problem diagnosis needed, no speed, smoke, low rpms - SailNet Community
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post #1 of 26 Old 01-09-2013 Thread Starter
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problem diagnosis needed, no speed, smoke, low rpms

I'm relatively new to sailboat maintenance and I've got problem. My engine is a Yanmar 75 turbo with a hurth v-drive and maxprop. boat is csy 44. I've been on a mooring for 5 months at st augustine and have not done any bottom maintenance since we arrived and planned on doing so only when we were moving the boat. I took the boat out for a short spin yesterday and could not get 1/4 knot of speed and would not tach up over 1500 rpms. I saw black smoke and some oil spitting out of the exhaust when trying to rev over 1500. The engine usually cruises at 2700 rpms. I dove under the boat very briefly due to very cold water and saw about 20 barnacles on the prop, small, but nothing that would cause that kind of performance. It seems like the shaft is somehow restricted. I didn't immediately see anything caught on running gear, but again, it was very cold. The speed was fine upon arrival in st augustine in August. I expected performance loss from growth, but not rpm restrictions. In neutral, it will tach up no problem. I have not changed the fuel filters yet. The performance issues are the same in forward and reverse. I will be under the boat tomorrow with a wet/dry suit and have more time, what should I look at? During the summer we were having a significant shaft vibration, I'm thinking maybe the cutlass bearing is going bad. Any thoughts would be appreciated.
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post #2 of 26 Old 01-09-2013
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Re: problem diagnosis needed, no speed, smoke, low rpms

I would try the simple fix first-- hire a diver to clean the prop, shaft, and the bottom. Also have him make sure there are no rope or fishing lines restricting the prop and shaft.
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post #3 of 26 Old 01-09-2013
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Re: problem diagnosis needed, no speed, smoke, low rpms

You problem is proababaly shaft related, whether its growth or cutlass.

I would venture to say if all was fine before it is growth. Its amazing how a few barnacles can retard the boat speed.

Thats the simple solution. More complicated could be shaft misalignment, a bad cutless bearing, or the coupling especially since you said you felt vibration, but again growth can cause that also. Think simple first.


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post #4 of 26 Old 01-09-2013
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Re: problem diagnosis needed, no speed, smoke, low rpms

Since we're all guessing here...

Since it ran correctly in August, I'm more inclined to think it's likely not an alignment or cutlass bearing issue. Prop wrap seems much more likely.

How about the v-drive? Can you freely turn the shaft by hand when the tranny's in neutral? Is the fluid at the proper level?


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post #5 of 26 Old 01-09-2013 Thread Starter
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Re: problem diagnosis needed, no speed, smoke, low rpms

I haven't tried to spin the shaft in neutral, I will tomorrow..The fluid level is normal, the transmission is rather loud going into and out of gear, I'm guessing that is because the shaft doesn't want to turn right away and the trannie has to provide alot of torque for the first rotation. The exposed shaft in the engine room is under the engine, kinda hard to get a hand on it, I will try to spin it from the prop under water. I've got a diver cleaning it up today. Is it common to drop 50% of your rpms just due to barnacles? If any growth was restricting the cutlass, wouldn't it have broken loose immediately. Just for arguments sake, if the running gear is clean, and nothing stuck on the prop, what else could cause the shaft to not want to rotate?
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post #6 of 26 Old 01-09-2013
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Re: problem diagnosis needed, no speed, smoke, low rpms

Its the bottom and the prop growth.

Don't worry about expensive things like cutless barings, shafts and engines. it will be the barnacles on the prop and grown on the bottom.

First Mate Yachting Services have a diver contracted to them. Give them a yell and get your bottom done then give it another go. It's a cheap, simple cure to what appears to be a huge problem.




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Last edited by MarkofSeaLife; 01-09-2013 at 09:40 AM.
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post #7 of 26 Old 01-09-2013
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Re: problem diagnosis needed, no speed, smoke, low rpms

My first suspension is that a fishing line may be causing that shaft not to spin properly. However after you dive on the boat and can turn the shaft while in neutral that would rule that out. I too have a max prop and while it has been flawless in the past 25 years of use just as a check make sure that it is rotating properly.
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post #8 of 26 Old 01-09-2013
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Re: problem diagnosis needed, no speed, smoke, low rpms

I think the first thing I would do is get a pair of good gloves and a paint scraper, scrub brushes, scrubbing pads, put on a mask and fins to try cleaning it up a bit myself to see if that makes a change.

It seems deferring maintenance is never a good idea.
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post #9 of 26 Old 01-09-2013
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Re: problem diagnosis needed, no speed, smoke, low rpms

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Originally Posted by thegreenflash View Post
I haven't tried to spin the shaft in neutral, I will tomorrow..The fluid level is normal, the transmission is rather loud going into and out of gear, I'm guessing that is because the shaft doesn't want to turn right away and the trannie has to provide alot of torque for the first rotation. The exposed shaft in the engine room is under the engine, kinda hard to get a hand on it, I will try to spin it from the prop under water. I've got a diver cleaning it up today. Is it common to drop 50% of your rpms just due to barnacles? If any growth was restricting the cutlass, wouldn't it have broken loose immediately. Just for arguments sake, if the running gear is clean, and nothing stuck on the prop, what else could cause the shaft to not want to rotate?
Can't you grab the prop shaft where it comes out of the back side of the Hurth V drive on the shaft coupling rather than try and reach under the engine?
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post #10 of 26 Old 01-09-2013
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Re: problem diagnosis needed, no speed, smoke, low rpms

I would guess the max prop is stuck in the feathered position. Doesn't take much growth to keep the blades from rotating. My brothers Auto prop was stuck from non-use, had the same symptoms you are describing.
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