2004 2 stroke hpdi 150 Yamaha "revved" at about 30 mph twice

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firemeddic

Recruit
Joined
Jul 9, 2011
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2
About 250 hours on my Yamaha 150 2 stroke. Ran fine all day before and after incidents. best way to explain is driving at about 2800 rpm and sounded like I went through a giant air bubble. Sounded like it was revving at 4500 rpm. I backed down the the throttle chrcked the cotter pin on the prop. It revved so loud I thought I lost the prop. anyone with a similar experience or an idea of what the problem might be would be appreciated. Engine did start right back up after each incident.
Regards and thanks
Sam:
 
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Bob Gilvary

Petty Officer 1st Class
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Apr 9, 2009
Messages
241
Re: 2004 2 stroke hpdi 150 Yamaha "revved" at about 30 mph twice

In a turn with the motor trimmed too high, spun prop? Seems like a cavitation issue from operation. Spun props don't fix themselves.
 
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seahorse5

Rear Admiral
Joined
Jan 24, 2002
Messages
4,698
Re: 2004 2 stroke hpdi 150 Yamaha "revved" at about 30 mph twice

It could also be a situation where raw fuel got into the crankcase and the motor would rev up - often from the fuel pumps leaking through the diaphragms or form some other source.
 
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firemeddic

Recruit
Joined
Jul 9, 2011
Messages
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Re: 2004 2 stroke hpdi 150 Yamaha "revved" at about 30 mph twice

I did notice that my fuel water seperator looks pretty rusty. Could that be the issue?
 
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Bob Gilvary

Petty Officer 1st Class
Joined
Apr 9, 2009
Messages
241
Re: 2004 2 stroke hpdi 150 Yamaha "revved" at about 30 mph twice

Rusty looking filter, I doubt it would have anything to do with it, but change it before it rusts through and floods the bilge with gas. Ruptured fuel pump diaphragms don't fix them selves either. Raw gas will wash away the crankcase lubrication and cause engine failure, but that doesn't seem to be your problem. Your explanation still indicates operation of the boat.

"Ran fine the rest of the day after the two incidents".
 
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