Cigatoo
Guru
As sneed said you may be fine where you are. Not much difference between 7.5 and 8 knots
what size prop do you recommend?
- Thread starter jeff brown
- Start date
The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
As sneed said you may be fine where you are. Not much difference between 7.5 and 8 knots
O C Diver
Guru
- Joined
- Dec 16, 2010
- Messages
- 12,868
- Location
- USA
- Vessel Name
- Slow Hand
- Vessel Make
- Cherubini Independence 45
Seems to me, if they were supposed to check the prop size, the mistake is on them. For the money you've spent in the boatyard, I would ask them to short haul the boat and get you the prop information N/C. A short haul is just lifting the boat out of the water long enough to complete a simple task and then put it back in. For what you've spent so far, that should be a reasonable no charge request.Thanks everyone for the information!
I had the bottom stripped,barrier coated 2 coats of paint. Bow thruster and new windlass installed, Hull painted with awlgrip new stripes. I asked them to check the prop size for me because I saw chips in the pictures they sent me(I'm 1200 miles away). It didn't happen before it was put back in the water 2 weeks ago. I like my toys dialed in right, so doing all the testing with a junk prop won't really give me a perfect baseline anyway. I'm told there's hundreds of these boats out there that's why I asked for help . I figured I would look for one while there was no rush and put it on the next haul out. Then send the original out to rebuild.
Ted
jeff brown
Veteran Member
- Joined
- Sep 9, 2018
- Messages
- 73
- Location
- usa
- Vessel Name
- Fuhgedaboutit
- Vessel Make
- 1966 38 CC COMMANDER, 1976 42 California LCR , 1991 42 Holiday Mansion
prop
The term dialed in might sound like overkill, I admit that, but I'm an old Indy car driver. However, most of the recommendations are quite detailed. An 8 knot boat was mentioned not requiring to be dialed in. So with that in mind I'll absorb all your suggestions . Happy New year
Thanks you very much.
The term dialed in might sound like overkill, I admit that, but I'm an old Indy car driver. However, most of the recommendations are quite detailed. An 8 knot boat was mentioned not requiring to be dialed in. So with that in mind I'll absorb all your suggestions . Happy New year
Thanks you very much.
psneeld
Guru
I am not saying its foolish...its just that other uncontrolled variables will vary your speed and economy probably more than a less than perfect prop.
You may not even have an idea what they are for a long time so I was only suggesting like part of the crowd....there's probably a lot on your plate to worry about and tweaking the route can come in time at your convenience.
You may not even have an idea what they are for a long time so I was only suggesting like part of the crowd....there's probably a lot on your plate to worry about and tweaking the route can come in time at your convenience.
Maerin
Guru
If you're turning the rated WOT rpm, and you're not perceiving vibration, I'd propose that you're already "dialed in" to the extent that you need to dial in a trawler prop. If you know the WOT rpm, but don't have the spec on the prop, as others suggest, you're nowhere on the factual spectrum, and any attempt to spec a replacement prop without that information will not yield dialed in results. Y' gotta start with a known quantity, then your prop shop will have a starting point to know if and how they can improve performance. The best approach is to take the prop to them and have them scan it. Then you'll be on track for accuracy.
Hope it works out for you.
C lectric
Guru
And if there is existing damage get that repaired. The do your testing.
As already suggested get a diver to pull the prop and take it to the shop for repairs and the scan. Then you can do the suggested testing with a good, maybe not best, prop that won't skew results due to the damage. Damage will skew results depending upon what the damage is and how bad.
As already suggested get a diver to pull the prop and take it to the shop for repairs and the scan. Then you can do the suggested testing with a good, maybe not best, prop that won't skew results due to the damage. Damage will skew results depending upon what the damage is and how bad.
Nomad Willy
Guru
Fish53,
I have the original skewed blade prop de-pitched to get 3000rpm (rated). Getting alittle thin but blessed by my prop man.
Been running the MP Michigan for some time only overpitched 50-75rpm. Thrust seems to be a bit off (5%?) but that is standard w the MP. It is smooth and has gobs of reverse thrust. Also a std feature of the MP.
The MP is a symmetrical blade prop whereas the leading edge is the same as the TE except the TE is “sharper” and the leading edge more rounded. I plan on having my prop man taking out an inch of pitch and putting a bit of cup on the TE. The cup just to keep the rpm below 3100. I would never use cup on a trawler prop for any other reason. But I know of nobody that changes a prop pitch 1/2”.
You can see the symmetrical v/s skewed blades clearly in the pics.
Attachments
Last edited:
Nomad Willy
Guru
Fish,
The original prop on the Willard was 18X14. Max rpm 2750. Willard overpropped their boats like many other manufacturers of the day. I had an inch of pitch taken out and the max rpm came right up to 3000. The engine sounded better at any speed and my idle speed was noticeably slower. Not nearly as much “in and out” of gear shifting in the harbor. At any speed of course the engine was under less load. If boats have a personality she was more relaxed.
But the old Willard prop (don’t know who made it) was getting thin and there was definitely a bit of pink showing. Decided to get a new prop.
1st bought a nibral prop from a distributor in Florida. Design wise it was between the two props I have now. Didn’t like it and don’t remember why. Mostly probably because I didn’t have it long.
Bought the Michigan from Tacoma Propellers. The Michigan MP prop was machine pitched ...hence the name. There was the same pitch from the hub right out to the blade tip. That’s probably mostly why they are not as efficient as most skewed props. The other is the wide tips that have greater “spill-off”. I knew about the lower efficiency but in view of the fact that this prop was ppobably the most common prop on commercial boats that I saw out of the water in SE Alaska and Puget Sound Wa. I assumed the lower efficiency was not much because the prop was so widely used. Work boat’s typically use reverse gear in the work that they do so the better reverse thrust no doubt was in the mix of desirability.
Michigan told me the blade area of the MP was about the same as my old Willard prop so I told Tacoma Propeller to take an inch of pitch out so it would be very close load/rpm wise to the old prop and thus buth prop would be 18X13. Somebody at Tacoma Propeller dropped the ball and it didn’t get done.
However I assumed it had. Mostly because the MP actually looked like it had more blade area.
On the boat the MP was a little bit shy (it seemed) of thrust. And the rpm was down 100 or so. I thought most TF members would be happy overpropped 100rpm so I decided to run it till the next haulout. But in Alaska (Thorne Bay) we did most of our bottom things on the tidal grid and several years went by before we were hauled whereas it would be handy to take the prop to the prop man and check out the prop. That was after we moved from Ak to Wn state. The first thing the prop man did was put it on the jig and check the pitch. It was 14. Only then did I discover I had been running a 14” pitch prop thinking all the time it wa 13. At that time I just decided to put the old prop back on after my prop man said the old dog was good enough for normal service.
Now I still have the old dog on the boat and it’s performance is good except I’ve got to start backing down much sooner because of the loss of reverse thrust. But I’d like to get the newer MP back on the boat after taking out the inch of pitch that Tacoma Propeller said they’d done. Should be perfect (but few props are lucky enough to be perfect) but it’s winter andthe old dog’s working fine.
The top two pics are of the MP and the bottom pic is of the original Willard prop.
The original prop on the Willard was 18X14. Max rpm 2750. Willard overpropped their boats like many other manufacturers of the day. I had an inch of pitch taken out and the max rpm came right up to 3000. The engine sounded better at any speed and my idle speed was noticeably slower. Not nearly as much “in and out” of gear shifting in the harbor. At any speed of course the engine was under less load. If boats have a personality she was more relaxed.
But the old Willard prop (don’t know who made it) was getting thin and there was definitely a bit of pink showing. Decided to get a new prop.
1st bought a nibral prop from a distributor in Florida. Design wise it was between the two props I have now. Didn’t like it and don’t remember why. Mostly probably because I didn’t have it long.
Bought the Michigan from Tacoma Propellers. The Michigan MP prop was machine pitched ...hence the name. There was the same pitch from the hub right out to the blade tip. That’s probably mostly why they are not as efficient as most skewed props. The other is the wide tips that have greater “spill-off”. I knew about the lower efficiency but in view of the fact that this prop was ppobably the most common prop on commercial boats that I saw out of the water in SE Alaska and Puget Sound Wa. I assumed the lower efficiency was not much because the prop was so widely used. Work boat’s typically use reverse gear in the work that they do so the better reverse thrust no doubt was in the mix of desirability.
Michigan told me the blade area of the MP was about the same as my old Willard prop so I told Tacoma Propeller to take an inch of pitch out so it would be very close load/rpm wise to the old prop and thus buth prop would be 18X13. Somebody at Tacoma Propeller dropped the ball and it didn’t get done.
However I assumed it had. Mostly because the MP actually looked like it had more blade area.
On the boat the MP was a little bit shy (it seemed) of thrust. And the rpm was down 100 or so. I thought most TF members would be happy overpropped 100rpm so I decided to run it till the next haulout. But in Alaska (Thorne Bay) we did most of our bottom things on the tidal grid and several years went by before we were hauled whereas it would be handy to take the prop to the prop man and check out the prop. That was after we moved from Ak to Wn state. The first thing the prop man did was put it on the jig and check the pitch. It was 14. Only then did I discover I had been running a 14” pitch prop thinking all the time it wa 13. At that time I just decided to put the old prop back on after my prop man said the old dog was good enough for normal service.
Now I still have the old dog on the boat and it’s performance is good except I’ve got to start backing down much sooner because of the loss of reverse thrust. But I’d like to get the newer MP back on the boat after taking out the inch of pitch that Tacoma Propeller said they’d done. Should be perfect (but few props are lucky enough to be perfect) but it’s winter andthe old dog’s working fine.
The top two pics are of the MP and the bottom pic is of the original Willard prop.
Last edited:
Nomad Willy
Guru
Fish,
I’m running a Mitsubishi S4L2 universal service diesel engine that usually finds itself on small front end loaders and other industrial applications.
Bore and stroke of 92X78. The same as the old 4-107 Perkins that we replaced. Cylinder head design is like the old Perkins also w a pocket pre-chamber where the fuel in injected. This design typically has glow plugs to assist starting. That was high on my desireability list thinking soon we’d be in some remote place in Alaska starting our engine in the morning when it was quite cold. The S4L2 was a plain jane design w no modern features.
I also was strongly drawn to the Mitsu marinized by Klassen because they provided a special steel exhaust manifold. They rust so slowly that almost none have ever been replaced. They have been using the steel manifolds since the 60’s. This engine was widely used for generators in the northern fishing fleet. I had corrosion proplems on my Yanmar on my previous boat and was looking to an engine w no aluminum. FYI Vetus and Westerbeke offer the same S4L2 engine but w aluminum manafolds.
This engine is rated at 37hp at 3000rpm. We use a BW gear (2.57-1) w some internal mods due to the low power. The BW gear is also used on engines w 200 and more hp. 1 1/4” prop shaft.
I’m running a Mitsubishi S4L2 universal service diesel engine that usually finds itself on small front end loaders and other industrial applications.
Bore and stroke of 92X78. The same as the old 4-107 Perkins that we replaced. Cylinder head design is like the old Perkins also w a pocket pre-chamber where the fuel in injected. This design typically has glow plugs to assist starting. That was high on my desireability list thinking soon we’d be in some remote place in Alaska starting our engine in the morning when it was quite cold. The S4L2 was a plain jane design w no modern features.
I also was strongly drawn to the Mitsu marinized by Klassen because they provided a special steel exhaust manifold. They rust so slowly that almost none have ever been replaced. They have been using the steel manifolds since the 60’s. This engine was widely used for generators in the northern fishing fleet. I had corrosion proplems on my Yanmar on my previous boat and was looking to an engine w no aluminum. FYI Vetus and Westerbeke offer the same S4L2 engine but w aluminum manafolds.
This engine is rated at 37hp at 3000rpm. We use a BW gear (2.57-1) w some internal mods due to the low power. The BW gear is also used on engines w 200 and more hp. 1 1/4” prop shaft.
Last edited:
Sounds like 37hp is working good for you. I don't know what your boat weighs and of course it's quite a bit larger than mine. Mine I believe will weigh about 7000lbs. when finished and I'm using a two cylinder Lister Petter LPWS which rather than using the 20hp @ 3000rpm rating I'm putting a fuel stop at 2600 which will be 18hp intermittent and 16.7 continuous. I have a 3 to 1 PRM150 hydraulic gear to a 1.25" shaft and a 18x14 three blade propeller. The boat originally had a Perkins 4-108 with a BW 72c 2.57 to 1 which was turning a 17x16 four blade prop. With the Perkins the boat had way more power than it needed but of course it was a military boat designed to carry 20 men and two crew.
ssteakley
Member
- Joined
- Aug 5, 2016
- Messages
- 19
- Location
- United States
- Vessel Name
- SNOWBALL
- Vessel Make
- Catalina 36 Mark II
Mtoa
Join the Marine Trader Owners Association, you can get the right answer there
https://mtoa.clubexpress.com/content.aspx?sl=1076077805
Having. Hundreds of owners respond who own the exact same vessel is priceless.
Join the Marine Trader Owners Association, you can get the right answer there
https://mtoa.clubexpress.com/content.aspx?sl=1076077805
Having. Hundreds of owners respond who own the exact same vessel is priceless.
foreverunderway
Senior Member
Every prop manufacturer has a form you can fill out online at no charge which, if you have all the pertinent information, should give you their recommended prop for your boat.
Do several and see what the professionals have to say.
Your boat or someone with the identical boat could have lots of changes over the 40-year lifespan of this boat. One may have a different trany, gear ratio or shaft size, which will lead you astray.
Do several and see what the professionals have to say.
Your boat or someone with the identical boat could have lots of changes over the 40-year lifespan of this boat. One may have a different trany, gear ratio or shaft size, which will lead you astray.
Several prop shops I've talked to just use the Boatdiesel calculator. I've checked a number of props on Boatdiesel and then did the calculation using Dave Gerr's Propeller book and they all matched. The advantage of having a prop shop spec your propeller would that if it's wrong they I assume would make it right, never having had that scenario I'm not sure though.
Is that a Walters keel cooler hiding behind that rebar?
Yes, The boat was built for me in 1982 by Yank Boat Works of Tuckerhoe.NJ. My friend Walter who worked at Lehman was able to get me the engine, keel cooler, prop, 2 inch shaft, at Lehman cost. Yanks Boat Eorks did
the steel work. The original mast came off a USCG 30 footer that I ran boat while in the CG. As built in 1982 the paint came from TEXACO Marine where I worked as mate on the tug TEXACO Sky Chief. Named after my son the boat is surely a "One Piece At A Time" boat. Lol
the steel work. The original mast came off a USCG 30 footer that I ran boat while in the CG. As built in 1982 the paint came from TEXACO Marine where I worked as mate on the tug TEXACO Sky Chief. Named after my son the boat is surely a "One Piece At A Time" boat. Lol
foreverunderway
Senior Member
I can't count the number of times I've had to have a prop shop tweak (change the pitch) a new prop to get absolutely the best performance out of it. The actual tweaking is usually included in the deal, if necessary, but if you are not a diver that end can get a bit expensive.
I just let the tide go out if I need to remove/replace my props. The only time I've ever had to have the pitch changed on a prop was when I bought a used prop from another boat an inch or so off on pitch.
I almost bought a little tug similar to yours, it had a Detroit 110 and was 31'. I was thinking of doing commercial towing on the Erie canal. I used to live near the canal in Spencerport, sort of a nostalgia thing. Nice boat.
Jeff -- there are a lot of good information being supplied by members is great but I will guarantee you will never reach your desired goal if the tachometer is not calibrated properly -- for about $35 you can buy an optical tach and make sure the tach you are propping to is reading correctly. Saves a boat load of money in wrong props.
Great point, I think I paid a bit more than that for mine ($200?) but it's a handy tool. Another thing that's quite helpful is a pyrometer which can be had for around $100.00 and gives a much better indication of engine load.
Last edited:
garycasey
Veteran Member
Just to add what might be useless information, I like to evaluate what's known as "propulsion efficiency." That's nothing more than the speed of the boat divided by the speed it would go if the prop was not slipping in the water. The efficiency of my sailboat prop was about 55%, my tug is 65% and airplane propellers are about 85%. So, at 10 knots, 2500 rpm, 2.5 gearbox, 65% propulsion efficiency gives a prop pitch of 18.6 inches. Interesting how close it is to the other answers. The equation is: Pitch(in) = boat speed(kts) X gear ratio X 1207(constant) / engine speed(rpm) / propulsion efficiency.
FF
Guru
- Joined
- Oct 12, 2007
- Messages
- 22,552
The hardest item to enter in most calculations is the actual weight of the boat.
Perhaps selecting a yard that can weigh the boat for the next bottom job might pay ?
Perhaps selecting a yard that can weigh the boat for the next bottom job might pay ?
Last edited:
