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Old 06-28-2014, 01:30 PM   #81
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Well said Mule, your savvy mechanic hit the nail on the head.
It is also surprising when changing air filters just how much dust they do accumulate, even way out at sea.
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Old 07-03-2014, 10:35 AM   #82
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I haven't done that yet, I too think running a cleaner through the system couldn't hurt. I know the hoses and heat exchangers are all clean as they are all new but the block, water jacket and tank could probably use a good chemical scrubbing.
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Old 07-03-2014, 10:37 AM   #83
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Originally Posted by manyboats View Post
Seems to me you should have 2.5-1 gears or a 3 blade like the stock boat. Just a case of too much blade area or not enough torque to turn the prop w the extra blade on it.

The stock boat is supposed to have 2-1 gears and a 3 blade prop.

Wxx3 wrote;
"According to the IG owners manual for 36' boats the standard issue for Lehman 120's on IG's is a gear box of 2:1 with 3 blade 24" props with a 16" Pitch. This is what my boat runs."

Why is this still a mystery? Or have I missed something?

jleonard is getting his rpm and performance w a 4 blade but only 20" in dia. Three inches in dia is a huge difference in load.
Eric, what kind of speed are you getting? Not that your hull will at all compare to my hull speed, just curious. I do think my prop guy was wrong and I intend on confronting him on the issue.
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Old 07-03-2014, 10:41 AM   #84
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Originally Posted by Irish Rambler View Post
Based on my own experience many boat engines don't have an efficient air filter, dirty air will wear the engine.
When talking of props and rpm I notice no one has mentioned the all important toque curve of the engine.
Personally I would use vicprop.com to calculate your prop, they've never been wrong on any I've done but as someone pointed out it doesn't take account of all the 'extra's & boys toys' we pile on adding extra weight.
I over prop to drop the rpm by 250 rpm and if necessary can run WOT for a half hour if I need to get out of trouble.
Yes, Rolls-Royce did actually test to destruction in many ways, you wouldn't believe the abuse a diesel will take before blowing. it's phenomenal.
The air filter is completely clean, I even ran it without just to be sure. I also have heard that a dirty filter will cause all of these symptoms. Thanks for the suggestion of vicprop.cm, I definitely give it a shot.
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Old 07-03-2014, 10:44 AM   #85
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personally I would not worry about your propping. It will give a surveyor something to complain about if you ever sell. the OP is by 600 RPM or more depending on which number you accept.

How big is your engine, 120HP??
Yes, its 120hp. I think the over propped load that it is causing thje engine is causing the exhaust to run hot (don't have a pyrometer to confirm) but a loaded engine will have hotter exhaust (you won't see it in your gauges so much) but this may be where the steam is coming from.
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Old 07-03-2014, 10:49 AM   #86
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Prop

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The most likely cause is over propping. The IP guy wasted your money.

Look at any engine curves and you will see a max output power curve and a prop demand curve. The prop demand curve is always lower on the graph than the max output curve. The curves meet only at max rpm. If the prop curve were higher than the max power curve the engine could not speed up. That is your condition.

Over propping means that you are loading the engine above the prop demand curve and probable hitting the max power output curve well below rated RPMs. The engine is putting out everything it can at that RPM. The problem is that the IP is set up to provide more fuel than needed by a prop curve at that lower RPM. That is the reason for more smoke. The engine is being given enough fuel to speed up but load wont allow it. Over fueling may cause hot combustion chambers and associated problems in addition to smoke. Smoke is good because it warns you that the engine is overloaded for its settings.

keep in mind that the same engine could be sold significantly derated HP to run at the RPM yours does but the fuel would be limited by the different IP settings to less than your current settings.

I suggest you take all your data to a good prop shop and ask their opinion on proper propping. You may find some calculators on the web but they are often for planning boats.

There will always be debate about over propping to save fuel but in reality each engine uses X amount of fuel to produce Y HP at any rpm it can reach within normal operating range. It is my opinion that over propping will generally use a bit more fuel at a particular load because the engine is being given extra fuel to allow increasing RPM that the load will not allow.
If you look at the fuel used on the two curves you can see that the engine can use the same amount of fuel at different RPM points on each curve.

Lower propping provides faster spin up which IMO gives quicker response when maneuvering and pushing through steep head seas.
Excellent info, thanks. I do think it is still an over propping issue. The engine checked out perfectly. At the suggestion of Brian at American Diesel, I even had the injector pump removed and sent off for calibration (thinking it could be a fuel delivery issue or timing issue). Turns out the pump is PERFECT! They didn't need to do anything to it. Another huge waste of money. Fuel, oil filters al new, new cooling system including the new lehman raw water pump (just in case), new hoses, new coolant. Based on all this, the boat has too much prop.

Obviously the only way to confirm this is to turn the prop down again, I just need to get my prop guy to do it for free now since I completely relied on him to get the correct size the first time. $800 to him plus another $150 to my diver to take the prop off and then put it back on! Ahhh! I'm going crazy over this whole thing!!!!
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Old 07-03-2014, 11:41 AM   #87
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RichF wrote;
"Eric, what kind of speed are you getting? Not that your hull will at all compare to my hull speed, just curious. I do think my prop guy was wrong and I intend on confronting him on the issue."

I get a max around 7 knots and cruise at 6.15. But I have only 40hp and a full disp heavy 30' hull. I do max out at 3000rpm at WOT. Run 2300 at cruise.

I think your problems would be over if you adjust your engine load to allow your Lehman to max at 2500rpm. Did you ever firm up the gear ratio? If you've got 2-1 you need 3 blade props IMO.
OK I read back and see you have confirmed the 2-1 gear ratio. Think 3 blade props. If you get real lucky you could find them used but ....

I went back all the way to your #1 post. It seems you have tried the 23" three blade prop and only got 2000rpm. Is that correct? And I gather you're a single engine boat. If that's so I'm not sure what to say and I'm not often speechless.
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Old 07-03-2014, 12:12 PM   #88
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RichF wrote;
"Eric, what kind of speed are you getting? Not that your hull will at all compare to my hull speed, just curious. I do think my prop guy was wrong and I intend on confronting him on the issue."

I get a max around 7 knots and cruise at 6.15. But I have only 40hp and a full disp heavy 30' hull. I do max out at 3000rpm at WOT. Run 2300 at cruise.

I think your problems would be over if you adjust your engine load to allow your Lehman to max at 2500rpm. Did you ever firm up the gear ratio? If you've got 2-1 you need 3 blade props IMO.
OK I read back and see you have confirmed the 2-1 gear ratio. Think 3 blade props. If you get real lucky you could find them used but ....

I went back all the way to your #1 post. It seems you have tried the 23" three blade prop and only got 2000rpm. Is that correct? And I gather you're a single engine boat. If that's so I'm not sure what to say and I'm not often speechless.
Yes, single engine and yes I did also try a 3-blade although it was a large 3 blade). I just talked to my prop guy and he is standing by his choice on the new prop size he gave me. (23x15-14; 4-blade) I told him to humor me and say he is wrong, what size would I need to get to 2,500 rpm if the one he made for me was only getting me 2,000 rpm. He said look for a 3 blade 22" x 14", 15" or 16" pitch. I just talked to the guys a Vic Prop too and here are their calcs. What do you know, calling for a 22"x15"-16" THREE blade, smaller size and pitch if I want a 4 blade but that's a pretty much impossible prop to find. So now I go prop hunting....

Could have bought a nice new electronics package with what I have wasted on money here....

I'll post back later with results (no doubt I am NOT the only guy out there having this issue). I sure hope this info. will help some other poor soul...
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Old 07-03-2014, 02:18 PM   #89
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RichF,
Apologies I don't wish to be rude but time spent on reconnaissance is never wasted.
I'm glad the guys at Vic prop sorted your problem, they're very helpful.
Put a few ads out for the prop you want but bear in mind that any s/hand prop will need checked and balanced BEFORE fitting.
Like you I couldn't get a 4 blade so I got one made, don't discount it, shop around and you may just find one.
Good Luck.
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Old 07-03-2014, 02:43 PM   #90
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RichF,
Apologies I don't wish to be rude but time spent on reconnaissance is never wasted.
I'm glad the guys at Vic prop sorted your problem, they're very helpful.
Put a few ads out for the prop you want but bear in mind that any s/hand prop will need checked and balanced BEFORE fitting.
Like you I couldn't get a 4 blade so I got one made, don't discount it, shop around and you may just find one.
Good Luck.
I know, its just super frustrating. I know everything I have done to the boat are good things to have had done and I know my engine better than ever, it would have just been nice to have resolved this months ago.

I may have already found a 22x16 3-blade for only $99 locally. I'll give it a test first and if it works I'll spend some money on it having it tuned and balanced. Fingers crossed!
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Old 07-03-2014, 03:00 PM   #91
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I hope it comes good for you. I know from experience how frustrating it can be when you are trying to resolve a problem and it doesn't go as quickly as you hoped.
Perseverance pays off though because you've self taught yourself more about your boat than you ever knew before and that will stand you in good stead some day.
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Old 07-03-2014, 05:41 PM   #92
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Call Marine Connection, Fort Pierce, Fl. They have hundreds if not thousands of props. 772 265 6460.. They are liquidators tha buys up inventory. You can work with improper shaft size with prop machining or bushings. See if they have something close then talk to ur prop guy. Also Dons Marine salvage in Clearwater Fl. 20 acre marine junk yard but their props are semi organized.
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Old 07-23-2014, 01:25 PM   #93
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Speed and RPM dilemma on 36 Island Gypsy - YouTube

I put this vid on from a few weeks ago. The temp issue must have been a lose wire. I was going to change the sender unit so I was poking around to get a part number (didn't think anything of it). The next weekend the temp never went above 195F. Nothing changed! The only thing that might have happened is that I jiggled the wire a bit and it works. Anyway they doesn't solve the prop issue. I am buying a new prop, I'll post the performance as soon as I get it on and tested.
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Old 07-23-2014, 05:15 PM   #94
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You need to check your temps with a mechanical gauge or an IR gun. 195 Deg. is a bit on the high side. If that temp. reading is accurate.
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