1984 150 johnson after 30 mph

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mahan1957

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Need Help, hit some rocks at dock and ever since when I get to around 30 mph and try and go faster the motor seems to rev up but the boat doesn't go faster and in fack loses it's grip, have fixed the prop and also installed a new hub but it is still doing the same thing, I looked at the inner parts on part sheet and there is a clutch dog, spring, and pin could this be the problem or maybe the gears themselves....Thanks for any advice
 
Joe Reeves

Joe Reeves

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Re: 1984 150 johnson after 30 mph

If there was a problem with the gears, dog, etc, it would feel like you were hitting a submerged object every so often. Assuming that your propeller was re-hubbed properly................

If this engine ever ran properly on the boat in question, then I would suspect that either something has come loose on the outer hull that is throwing a air pocket into the propeller OR someone has added something to the hull/transom which would do the same thing.

If this rig is new to you, and the hull & transom etc are as they should be, then I'd suspect that the engine is mounted too high on the transom and is cavitating.
 
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mahan1957

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Re: 1984 150 johnson after 30 mph

The motor height is the same, however about the same time this all started happening A transducer for lowrance structure scan was installed on the bottom back of the transom, you think that this long transducer could be throwing air pockects to the prop and it's that simple?
 
Joe Reeves

Joe Reeves

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Re: 1984 150 johnson after 30 mph

Absolutely, and therein lies the problem. I've encountered that many times.
 
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mahan1957

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Re: 1984 150 johnson after 30 mph

Well, back to square 1. Moved all the transducers from the back bottom were the is nothing but the back of the boat and the motor and it still wants to over rev and lose it's grip after about 30 mph. Hope some one has encountered this before and has a fix..... Thanks
 
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hidef

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Re: 1984 150 johnson after 30 mph

I have you tried a different prop?
 
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mahan1957

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Re: 1984 150 johnson after 30 mph

The prop that was hit on the rocks has been repaired and I also purchaced another one for a back up and it doesn't make any difference
 
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mahan1957

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Re: 1984 150 johnson after 30 mph

mahan1957 said:
The prop that was hit on the rocks has been repaired and I also purchaced another one for a back up and it doesn't make any difference
Click to expand...

The prop shaft seems to have a pretty good wable now and when in gear and turning the prop by hand you can here a grinding in the lower unit about where the gears are? any thoughts?
 
Joe Reeves

Joe Reeves

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Re: 1984 150 johnson after 30 mph

If you have a bent propshaft, that'll need to be straightened out professionally by a propeller repair or machine shop, and to do that you'll need to remove and dismantle the gearcase anyway which will reveal any internal gearcase damage.
 
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