Prop size and pitch
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Asuming the 5.2 kts at 2,200 rpm is at full wot throttle, then something is wrong. That engine should turn 2,600 at wot. Even if overpropped by 400 rpm I would have thought most single engine trawlers would go much faster, closer to 7 kts.
The easiest thing to check and maybe the most likely is that the throttle isn't opening all of the way and it should be a simple adjustment to fix it.
The other possibility is a very dirty bottom and/or a fouled prop. The exhaust riser could be plugged with scale and soot which will limit power and rpms. Also the filters could be clogged which restricts fuel.
Check all of these things before you think about tackling the prop.
David
The easiest thing to check and maybe the most likely is that the throttle isn't opening all of the way and it should be a simple adjustment to fix it.
The other possibility is a very dirty bottom and/or a fouled prop. The exhaust riser could be plugged with scale and soot which will limit power and rpms. Also the filters could be clogged which restricts fuel.
Check all of these things before you think about tackling the prop.
David
I understand that the engine revs up to 2800 rpm and there is a little left in the throttle. That’s why a suspect that it is under proped..everything I read shows around 1800 revs gives about 7 knots with the boats and similar hp engine..
Comodave
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If it is turning 2800 in gear at full throttle it may be a bit under pitched but not that much to only get 5.2 kts at 2200. I suspect there is something else like was mentioned before maybe a fouled bottom.
Also what is the boat. Single Perkins are found in up to 34' trawlers usually. Those should easily get up to 7+ kts with the Perkins running in the low to mid 2000s. What is your wot rpm and speed?
Still sounds like a fouled bottom to me.
David
Still sounds like a fouled bottom to me.
David
High Wire
Guru
My 36 with Perkins 135 goes 6.8 knots at 1650 RPM with 25"D X 22"P 3 blade. Yes it is over propped. Even with 1/2" of barnacles it only cuts that down to 6.3 knots.
Something is seriously wrong at 5.2 knots at 2200 rpm.
What is the transmission ratio?
BTW a Perkins 135 is a 2800 WOT engine.
Something is seriously wrong at 5.2 knots at 2200 rpm.
What is the transmission ratio?
BTW a Perkins 135 is a 2800 WOT engine.
Ross Woodhouse
Newbie
I own a 36' Grand Mariner with a Ford Lehman 120 HP with a 24"x 18" with a 1" cup. She runs at 1750RPM at a steady 7 knots burns about 6 litres/hr.
High Wire
Guru
At could also be that tach is reading too high. It is driven by the alternator so things that effect the alt speed, also reflect in the tach rpm. Worn belts, too small alt pulley or maybe someone tweeked the tach adjustment screw.
One quick look at the waterline will tell the dirty bottom story.
Cruise RPM is too high AND cruise speed too low!!!
One quick look at the waterline will tell the dirty bottom story.
Cruise RPM is too high AND cruise speed too low!!!
Last edited:
STB
Guru
Is it smoking when warmed up at cruise? I'd expect black smoke if a bottom issue or over propping or some other cause of overloading.
Buy a digital tachometer; https://www.amazon.com/Digital-Photo-Laser-Tachometer-Contact/dp/B001N4QY66
Calculate your propeller size; https://www.vicprop.com/calculator.htm
Doubt you are underpropped. Verify actual rpms on pulley and prop shaft first. Could be slipping transmission? Build a graph of rpm v. gps speed at slack tide. Should be linear until you start approaching WOT.
Calculate your propeller size; https://www.vicprop.com/calculator.htm
Doubt you are underpropped. Verify actual rpms on pulley and prop shaft first. Could be slipping transmission? Build a graph of rpm v. gps speed at slack tide. Should be linear until you start approaching WOT.
kapnd
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A quick check you need to do is to run the motor up to full throttle in neutral, and note the indicated rpms.
If it won’t make 2800 and likely a little more, a tach check is the next step.
Exhaust gas temperature measurement can be very helpful in propeller tuning too.
Clean bottom and running gear, chart all available info at 200 rpm intervals, then run your numbers on the prop calculator mentioned above.
I would not be surprised to find that it’s overpropped, it’s common throughout the pleasure craft industry to do so.
If it won’t make 2800 and likely a little more, a tach check is the next step.
Exhaust gas temperature measurement can be very helpful in propeller tuning too.
Clean bottom and running gear, chart all available info at 200 rpm intervals, then run your numbers on the prop calculator mentioned above.
I would not be surprised to find that it’s overpropped, it’s common throughout the pleasure craft industry to do so.
I am a little confused..if the engine is running at 2200 rpm and only getting 5.6nm wouldn’t that indicate it could be underpropped not overpropped? In any event I bought and received laser tac and we will see next week what is going on. I will use my gps phone to see the true speed and the tac to see the true rpm. Will also verify wot and note rpm and speed. Also verify shaft rpm and trans gear ratio. With all of this might be able to figure out something.
Comodave
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If you are not reaching the proper max RPM then you are overpropped if everything else is correct, bottom not dirty, etc. if you were under propped then you would be turning more than the proper full RPMs.
rsn48
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I also agree, low rpm's not high enough then an excellent chance your boat is over propped. My old boat came over propped, the last owner pretty much bragged about it, instructed me not to take the boat to WOT as it would stress the motor.
Why people over prop is a mystery to me, I don't think they understand what over propping can do to the motor.
Why people over prop is a mystery to me, I don't think they understand what over propping can do to the motor.
Tiffany
Veteran Member
My Apollo 32 with 6-354 Perkins and 22 X 24 prop
My Apollo 32, with a clean bottom, and new Michigan Wheel 4 bladed 22" X 24 pitch pushes along at 4.2 knots at 550 RPM / idle and 8 knots runs at 1,100 RPM. My 1982 Perkins T6-354 manual says that only short runs under an hour at 2,250 RPM. Given the semi displacement hull, I can't imagine getting the boat to reasonably achieve that engine speed, let alone 2,600.
I went through numbers with three different prop shops and their calculators. All returned very close similar numbers to what we settled on for speed, engine power and economy. 2,200 RPM is no where near what works for an old Perkins.
My Apollo 32, with a clean bottom, and new Michigan Wheel 4 bladed 22" X 24 pitch pushes along at 4.2 knots at 550 RPM / idle and 8 knots runs at 1,100 RPM. My 1982 Perkins T6-354 manual says that only short runs under an hour at 2,250 RPM. Given the semi displacement hull, I can't imagine getting the boat to reasonably achieve that engine speed, let alone 2,600.
I went through numbers with three different prop shops and their calculators. All returned very close similar numbers to what we settled on for speed, engine power and economy. 2,200 RPM is no where near what works for an old Perkins.
Perkins made many different engines. It may be capable of 2800 WOT intermittently and 2400 continuous. I suspect OP has T6-354-4 but he doesn't list the model.
I believe the OP's goal is to make a simple graph of rpm and speed. If he can reach 2800 rpm at idle, but can't reach 2800 rpm under way, then it might be an indication that he is over propped.
dardurfr
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I have a Perkins 135 naturally aspirated in my boat but also have the same issue with the rpm's. Revs fine in neutral(2800) but in gear barely makes 2200rpm. Not sure the size of the prop. It does carry a little bit of smoke on start up for the first 5-10 minutes but my mechanic says if I can figure out how to stop that to let him know. Had the injectors done but made very little difference although they were fouled really bad, next step clean the bottom and check prop size. I do have a new fuel pump to put on but not sure if that would remedy the problem either. Anxious to hear his findings. Might give me something else to look for.
STB
Guru
Hi all,
My last boat had Perkins 6.354MGT engines, and my current boat has Perkins 6.354M engines. 185hp in the first case, 135 hp or so in the second case. I've spent a lot of time working with them.
My experience is that these are very straight-forward, old-school diesel engines. They need air and fuel and run on compression. And, if things go wrong or get out of balance, looking at how they start and at the smoke can tell you a lot.
If the fuel is good, the supply is unrestricted, the filters are good, the injector pump is good, and the injectors are good, the fuel gets a nice spray pattern and can burn completely. If, in isolation, something goes wrong with this, one thing that can happen is that the fuel doesn't get a nice spray pattern, gets fewer larger globs, and doesn't burn completely. This presents as lingering white smoke that smells like diesel and often times a slick on the water.
On the turbo models, especially the MGT, the pump over supplies fuel at idle and lower RPMs, which results in some white smoke and possibly slicking at idle -- but the engine catches up at relatively low cruising RPMs and this goes away. This is just a case of the pump and injector combination not having a curve that can align perfectly with the engine, so it was tuned for cruise not idle. So, if the only problem is at idle, it can safely be ignored on turbo models.
If the fuel filters get clogged (or there is some other constriction, or fuel is running low and not supplying well), this can present as being hard to start and/or white smoke. White smoke is possible because if things get really clogged, fuel supply is restricted and the injector pump can't create enough pressure for a good injector spray pattern. Another thing that can happen is that RPMs can surge. The restriction slows the flow of fuel so the governor opens up wider. Fuel rushes in, maybe past a by-pass, and the RPS surge to something appropriate for the governor that is open too much, and the governor closes down a bunch and RPMs fall. Wash rinse repeat.
If everything else is as it should be, but the air is restricted, the fuel will burn incompletely, because there is good fuel spray and enough compression to burn it - but not enough oxygen for the chemical reaction. So, the burning produces less energy and different chemicals as exhaust. The exhaust is filled with carbon and therefore has more dark grey and black. This can happen with a clogged air filter, but that is rare (Perkins don't always have air filters and engine rooms are relatively clean places). That can happen with Turbos if they aren't as efficient as they should be and aren't pushing as much air in as they should, leaving less oxygen than is needed for the fuel. It can also happen during brief periods when the load or throttle are initially advanced, as the turbo, which is driven by exhaust gases from before advance, needs time to "catch up" and develop the boost to push in enough air. It can also happen when the load is too high, e.g. by over propping or dirty bottoms. In this case the throttle is advanced supplying more fuel, but the load on the engine prevents it from getting higher RPMs. So, there is more fuel from the advanced throttle, but not enough RPMs to get enough air to burn it. In other words, the low RPMs from the load lead to a relative surplus of fuel and relative shortage of oxygen.
If an engine has low compression, this can show up as excessive white smoke, black smoke, or more likely both -- grey smoke. Basically, if compression is bad, fuel could be left unburnt or be burt badly.
If injector timing is off, the engine may be hard to start or produce white smoke, or both. Basically, injecting fuel too late or too early in the cycle will lead to it not all burning. On the 6.354, the timing is most commonly adjusted at the injector pump, but it can also be adjusted at the auxiliary gear and the auxiliary gear shaft.
Blue in the smoke is, as one would expect, motor oil working its way in, and burning.
Valve timing being off can lead to white smoke, especially if they are too tight. It chances the timing of the compression cycle, leading to fuel not being burned.
White smoke that doesn't linger and doesn't smell like diesel is likely coolant or raw water, e.g. a bad cooler or head gasket.
With no load, the max RPM is controlled by the governor setting on the injector pump.
So, if we take a naturally aspirated 6.354 engine and start it in moderate weather, we should see some smoke at the slip. They aren't precisely dialed in engines, ever. In a naturally aspirated engine, it is likely to be grey in color, which is a little white and a little black mixed. On a turboed engine, there is likely to be more smoke and it is likely to be more white in character -- more unburned fuel to the same incompletely burned fuel.
At cruise, this smoke should totally go away. In part, the engines should run cleaner. But, in part, the small amount of smoke is just spread out over distance instead of staying in one place. If one sees smoke at the low end of cruise, something is up. The color can help to diagnose it.
If the boat has enough more horsepower than it really needs, e.g. the 6.354MGTs in my old boat, as the boat gets past cruise range, it starts pushing into and climbing up the bow wave more and more. This load limits RPMs. The smoke starts to get darker and darker as one opens the throttles more and more. The boat can go faster, but runs dirtier and dirtier as it runs less and less efficiently.
The point at which this happens can come sooner if a load is imposed by a dirty bottom or over propping. But, the tell-tale for overloading is that smoke that was absent, white, or light grey becomes dark grey or black and much more prominent.
So, in my mind, one wants to get the boat cleaned really well and take the boat out and up to WOT. At this point, one should see some grey or black in the smoke. If not, the boat may be underpropped, underpowered, or have the governor set wrong. Underpowered isn't a problem. The governor set wrong can be adjusted by turning the screw at the slip. And, underpropped by a little isn't a big deal.
The next thing that one wants to do is to back down the throttle until the smoke, or at least the blackness/greyness, clears up completely, or as close to completely as it will. This will probably be about 80-85% of WOT RPMs. Now you've found your cruise speed.
If one has to lower RPMs much more than that, then the boat might be over propped. It could also be an older engines, be lower on compression, and just like to run at lower RPMs. But, even in this case, reducing prop pitch might let it run cleaner at higher RPMs.
Also, the entire underway part of this discussion assumes the transmission ratio is right for the intended use. Obviously, if that isn't matched, the boat can end up in the wrong RPM band for the load.
The boat that I own now had the same owners for many, many years. They cruised it very extensively at about 8kn. This is apparently what the prior owners had told them was its cruise speed. It is a little surprising since its hull speed is right about there, so one might assume a faster cruise speed. The next owner, who had the boat for about 3 years, wanted more speed out of it. He had the engines rebuilt and the props refurbished and dynamically balanced, etc. It cruised for him at -- about 8 kn. I bought the boat, figured it might run faster if only I wished it to, gave it a good tune up and took it out. You know where it wanted to cruise for me? 8.3kn.
Why is that an 8.3kn boat, not a 9.3kn boat? I don't know. Maybe I'll figure it out and understand. Or, maybe I'll figure it out and tweak it. But, probably not. The history is that it has been an 8kn boat since it was new. Most likely there is something about the hull shape or rudder drag or whatever that I don't understand. What I can say is this --
it runs nice and fuel efficient at 8kn, which is apparently what it was designed to do.
So, what I'm suggesting here is that:
1) I agree 100% with the suggestions to get a phototach to check RPM and use GPS or some other tool to check speed, as the speed instrument and tach gauge can easily be off. Good data is essential.
2) I wouldn't expect a Perkins 6.354 of any kind to reach it WOT (idle) speed underway. I've always seen the engines to have lower WOT RPMs under load than at idle. And, I've never seen black smoke to indicate this is a problem.
3) If true, that RPM does seem high to me and that speed does seem low to me, so I'm wondering about /under/ propping (not over propping or a dirty bottom).
4) There has been no discussion about the smoke or RPM stability here. And, that is really important data, especially the smoke color and volume at the slip, underway, at WOT, etc.
5) See #1. It is worth reading twice.
Cheers!
-Greg
My last boat had Perkins 6.354MGT engines, and my current boat has Perkins 6.354M engines. 185hp in the first case, 135 hp or so in the second case. I've spent a lot of time working with them.
My experience is that these are very straight-forward, old-school diesel engines. They need air and fuel and run on compression. And, if things go wrong or get out of balance, looking at how they start and at the smoke can tell you a lot.
If the fuel is good, the supply is unrestricted, the filters are good, the injector pump is good, and the injectors are good, the fuel gets a nice spray pattern and can burn completely. If, in isolation, something goes wrong with this, one thing that can happen is that the fuel doesn't get a nice spray pattern, gets fewer larger globs, and doesn't burn completely. This presents as lingering white smoke that smells like diesel and often times a slick on the water.
On the turbo models, especially the MGT, the pump over supplies fuel at idle and lower RPMs, which results in some white smoke and possibly slicking at idle -- but the engine catches up at relatively low cruising RPMs and this goes away. This is just a case of the pump and injector combination not having a curve that can align perfectly with the engine, so it was tuned for cruise not idle. So, if the only problem is at idle, it can safely be ignored on turbo models.
If the fuel filters get clogged (or there is some other constriction, or fuel is running low and not supplying well), this can present as being hard to start and/or white smoke. White smoke is possible because if things get really clogged, fuel supply is restricted and the injector pump can't create enough pressure for a good injector spray pattern. Another thing that can happen is that RPMs can surge. The restriction slows the flow of fuel so the governor opens up wider. Fuel rushes in, maybe past a by-pass, and the RPS surge to something appropriate for the governor that is open too much, and the governor closes down a bunch and RPMs fall. Wash rinse repeat.
If everything else is as it should be, but the air is restricted, the fuel will burn incompletely, because there is good fuel spray and enough compression to burn it - but not enough oxygen for the chemical reaction. So, the burning produces less energy and different chemicals as exhaust. The exhaust is filled with carbon and therefore has more dark grey and black. This can happen with a clogged air filter, but that is rare (Perkins don't always have air filters and engine rooms are relatively clean places). That can happen with Turbos if they aren't as efficient as they should be and aren't pushing as much air in as they should, leaving less oxygen than is needed for the fuel. It can also happen during brief periods when the load or throttle are initially advanced, as the turbo, which is driven by exhaust gases from before advance, needs time to "catch up" and develop the boost to push in enough air. It can also happen when the load is too high, e.g. by over propping or dirty bottoms. In this case the throttle is advanced supplying more fuel, but the load on the engine prevents it from getting higher RPMs. So, there is more fuel from the advanced throttle, but not enough RPMs to get enough air to burn it. In other words, the low RPMs from the load lead to a relative surplus of fuel and relative shortage of oxygen.
If an engine has low compression, this can show up as excessive white smoke, black smoke, or more likely both -- grey smoke. Basically, if compression is bad, fuel could be left unburnt or be burt badly.
If injector timing is off, the engine may be hard to start or produce white smoke, or both. Basically, injecting fuel too late or too early in the cycle will lead to it not all burning. On the 6.354, the timing is most commonly adjusted at the injector pump, but it can also be adjusted at the auxiliary gear and the auxiliary gear shaft.
Blue in the smoke is, as one would expect, motor oil working its way in, and burning.
Valve timing being off can lead to white smoke, especially if they are too tight. It chances the timing of the compression cycle, leading to fuel not being burned.
White smoke that doesn't linger and doesn't smell like diesel is likely coolant or raw water, e.g. a bad cooler or head gasket.
With no load, the max RPM is controlled by the governor setting on the injector pump.
So, if we take a naturally aspirated 6.354 engine and start it in moderate weather, we should see some smoke at the slip. They aren't precisely dialed in engines, ever. In a naturally aspirated engine, it is likely to be grey in color, which is a little white and a little black mixed. On a turboed engine, there is likely to be more smoke and it is likely to be more white in character -- more unburned fuel to the same incompletely burned fuel.
At cruise, this smoke should totally go away. In part, the engines should run cleaner. But, in part, the small amount of smoke is just spread out over distance instead of staying in one place. If one sees smoke at the low end of cruise, something is up. The color can help to diagnose it.
If the boat has enough more horsepower than it really needs, e.g. the 6.354MGTs in my old boat, as the boat gets past cruise range, it starts pushing into and climbing up the bow wave more and more. This load limits RPMs. The smoke starts to get darker and darker as one opens the throttles more and more. The boat can go faster, but runs dirtier and dirtier as it runs less and less efficiently.
The point at which this happens can come sooner if a load is imposed by a dirty bottom or over propping. But, the tell-tale for overloading is that smoke that was absent, white, or light grey becomes dark grey or black and much more prominent.
So, in my mind, one wants to get the boat cleaned really well and take the boat out and up to WOT. At this point, one should see some grey or black in the smoke. If not, the boat may be underpropped, underpowered, or have the governor set wrong. Underpowered isn't a problem. The governor set wrong can be adjusted by turning the screw at the slip. And, underpropped by a little isn't a big deal.
The next thing that one wants to do is to back down the throttle until the smoke, or at least the blackness/greyness, clears up completely, or as close to completely as it will. This will probably be about 80-85% of WOT RPMs. Now you've found your cruise speed.
If one has to lower RPMs much more than that, then the boat might be over propped. It could also be an older engines, be lower on compression, and just like to run at lower RPMs. But, even in this case, reducing prop pitch might let it run cleaner at higher RPMs.
Also, the entire underway part of this discussion assumes the transmission ratio is right for the intended use. Obviously, if that isn't matched, the boat can end up in the wrong RPM band for the load.
The boat that I own now had the same owners for many, many years. They cruised it very extensively at about 8kn. This is apparently what the prior owners had told them was its cruise speed. It is a little surprising since its hull speed is right about there, so one might assume a faster cruise speed. The next owner, who had the boat for about 3 years, wanted more speed out of it. He had the engines rebuilt and the props refurbished and dynamically balanced, etc. It cruised for him at -- about 8 kn. I bought the boat, figured it might run faster if only I wished it to, gave it a good tune up and took it out. You know where it wanted to cruise for me? 8.3kn.
Why is that an 8.3kn boat, not a 9.3kn boat? I don't know. Maybe I'll figure it out and understand. Or, maybe I'll figure it out and tweak it. But, probably not. The history is that it has been an 8kn boat since it was new. Most likely there is something about the hull shape or rudder drag or whatever that I don't understand. What I can say is this --
it runs nice and fuel efficient at 8kn, which is apparently what it was designed to do.
So, what I'm suggesting here is that:
1) I agree 100% with the suggestions to get a phototach to check RPM and use GPS or some other tool to check speed, as the speed instrument and tach gauge can easily be off. Good data is essential.
2) I wouldn't expect a Perkins 6.354 of any kind to reach it WOT (idle) speed underway. I've always seen the engines to have lower WOT RPMs under load than at idle. And, I've never seen black smoke to indicate this is a problem.
3) If true, that RPM does seem high to me and that speed does seem low to me, so I'm wondering about /under/ propping (not over propping or a dirty bottom).
4) There has been no discussion about the smoke or RPM stability here. And, that is really important data, especially the smoke color and volume at the slip, underway, at WOT, etc.
5) See #1. It is worth reading twice.
Cheers!
-Greg
Last edited:
STB
Guru
Quick suggestions...
1) Note the units on your app, whether they are miles/hr or knots/hr. A knot is about 1.15 miles, so, if measuring in miles/hr, divide by 1.15 to Get knots/hr. Alternatively, multiply knots/hr by 1.15 to Get,miles/hr.
2) Try to run the boat along parallel paths in opposite directions pretty, close together in time and space. In one direction the water movement will push one way, in the other direction it will push the other. Nothing is perfectly symmetric, but the truth is pretty likely to be pretty close to the middle (average), especially if done in relatively calm water. To make it is easy for me to do, I usually go as close,to perfectly head in and then following as I can, rather than at angles. But, in any case, the compass is one's friend. Take the initial heading and go around 180 for the new heading. Try a couple or small few headings to get more data points, if there is time.
Cheers!
-Greg
1) Note the units on your app, whether they are miles/hr or knots/hr. A knot is about 1.15 miles, so, if measuring in miles/hr, divide by 1.15 to Get knots/hr. Alternatively, multiply knots/hr by 1.15 to Get,miles/hr.
2) Try to run the boat along parallel paths in opposite directions pretty, close together in time and space. In one direction the water movement will push one way, in the other direction it will push the other. Nothing is perfectly symmetric, but the truth is pretty likely to be pretty close to the middle (average), especially if done in relatively calm water. To make it is easy for me to do, I usually go as close,to perfectly head in and then following as I can, rather than at angles. But, in any case, the compass is one's friend. Take the initial heading and go around 180 for the new heading. Try a couple or small few headings to get more data points, if there is time.
Cheers!
-Greg
Nomad Willy
Guru
gkesden,
I usta do that often and I still do at times.
Re prop “size and pitch” per this thread subject the relationship of dia and pitch is IMO very important. Too many trawlers have too much dia and too little pitch. Probably from thinking 4 blade props are better than 3. Usually it’s not the case but the relationship between pitch and dia should be right for good performance. Exactly what is right I don’t know. But there may be a good relationship ratio number that could be applied to the average trawler. Then I think one would need lots of numbers from lots of variables but pitches like 24X24 is not something you’d want on a trawler. Nor would 32X18. Somewhere like 27X 22 would seem about right.
Too much dia and there’s too much drag from surface area of the blades and too much pitch results in too much tip loss from water spilling over the blade tips. The trick is to spec a prop that has about equal losses of each so the overall losses will be less .. or minimal.
I usta do that often and I still do at times.
Re prop “size and pitch” per this thread subject the relationship of dia and pitch is IMO very important. Too many trawlers have too much dia and too little pitch. Probably from thinking 4 blade props are better than 3. Usually it’s not the case but the relationship between pitch and dia should be right for good performance. Exactly what is right I don’t know. But there may be a good relationship ratio number that could be applied to the average trawler. Then I think one would need lots of numbers from lots of variables but pitches like 24X24 is not something you’d want on a trawler. Nor would 32X18. Somewhere like 27X 22 would seem about right.
Too much dia and there’s too much drag from surface area of the blades and too much pitch results in too much tip loss from water spilling over the blade tips. The trick is to spec a prop that has about equal losses of each so the overall losses will be less .. or minimal.
Last edited:
So the mystery is solved...the boats tacs are inaccurate as is the paddy wheel speed indicator. Using the laser tac and my navatronics app the rpm and speed is about what everyone says it should be. Bought the boat now need to figure out how to calibrate the tacs. Thanks for all your help.
STB
Guru
On many tachs, there is just a screw on the back that sets the ratio, e.g. the RPMs measured at the alternator or auxiliary shaft or wherever to engine RPM. On some, it "clicks" between fixed ratios, on others itbis a continuous adjustment. On some, there are jumpers to set that may (or may not) be labelled. In any case, you can almost always google and find the instructions.
Cheers!
-Greg
Cheers!
-Greg
