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post #1 of 17 Old 09-06-2008 Thread Starter
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Angry Low Power in Fwd

Hello all-

I seem to have run into an issue this morning regarding engine power in fwd gear. It seems the engine (81' Yanmar 2QM15) will not reach RPMs any higher than 1650 in forward gear. Reverse gear will top out at about 2300 RPMs while neutral will reach 2600+ with out issue. In forward gear the boat is very sluggish and at 1650 RPM generates a lot of black smoke and seemingly raw diesel in the exhaust as though it is not being burnt off properly.

All filters and strainers seem to be fine with a visual inspection and there are no noticeable vibrations or strange engine knocks, etc. I have verified both gear and throttle linkages and found no issues. The boat was hauled out the end of July and prop/bottom cleaned....is it possible my prop could be fouled already?

TIA
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post #2 of 17 Old 09-06-2008
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wouldn't be surprised if the prop is fouled.

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post #3 of 17 Old 09-06-2008
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Fouled prop sounds likely to me as well.

John
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post #4 of 17 Old 09-06-2008 Thread Starter
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Seems there are quite a few similar posts lately....tis the season I guess. Looks like I will be getting wet. I will let you know how it turns out. Thanks for the replies!!!

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post #5 of 17 Old 09-06-2008
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MSter can you put a boarding ladder over the side, put on goggles or a face mask & look at the prop? i had to do that on my boat & found the trouble right away. also if you have the correct pitch on the prop the engine should be able to get up to rated RPM.
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post #6 of 17 Old 09-06-2008
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You don't say where you are located but I can tell you that here in Western Long Island Sound (NY USA), my prop has had to be cleaned at least 4 times this season. The symptoms are similar to yours. good acceleration in neutral but everything bogs down once you put it in gear.

One of the bad things about clean water is that things grow well in it.

Cheers,

MikeR

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Hello all-

I seem to have run into an issue this morning regarding engine power in fwd gear. It seems the engine (81' Yanmar 2QM15) will not reach RPMs any higher than 1650 in forward gear. Reverse gear will top out at about 2300 RPMs while neutral will reach 2600+ with out issue. In forward gear the boat is very sluggish and at 1650 RPM generates a lot of black smoke and seemingly raw diesel in the exhaust as though it is not being burnt off properly.

All filters and strainers seem to be fine with a visual inspection and there are no noticeable vibrations or strange engine knocks, etc. I have verified both gear and throttle linkages and found no issues. The boat was hauled out the end of July and prop/bottom cleaned....is it possible my prop could be fouled already?

TIA
MSter...
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post #7 of 17 Old 09-06-2008
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If it turns out not to be a fouled prop, check the throttle control.

These things have eccentric cams that put the gearbox into gear and then begin advancing the throttle (unless you have an unlikely setup with two levers). It is possible that the throttle in reverse is operating smoothly achieving full stoke and in forward it is sticking on the eccentric. You may get the impression that you're getting full stroke on the throttle lever but in reality not.

Just another option, perhaps.

Andre
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post #8 of 17 Old 09-06-2008
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Andre;

That wouldn't cause the high torque, bog down creating the black smoke and over fueling ( Raw diesel in Exhaust ) though...
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post #9 of 17 Old 09-06-2008
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Same problem here...prop fouled with barnacles. Cleaned the prop and sail drive and off I went.

Cheers,

Bob

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post #10 of 17 Old 09-06-2008
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Is it possible that you have a dirty transmission filter? I was once told by a mechanic (don't know if it is true for all trannys or not) that when in reverse fluid isn't pushed through the filter. It sounds like your transmission may be bogging the engine down in forward gear. Something to check anyway.

Fouled prop just doesn't make sense to me. You would have equally bad performance from the prop in forward or reverse.

Jon Caisson Bozeman
S/V Little Miss Magic, Pirates Cove, AL
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