350 Chev OMC Loosing power at high RPMs - UPDATE

M

mtnrat

Chief Petty Officer
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Jul 29, 2006
Messages
419
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

When you check the fuel pick up in the tank, put in fresh gas.
 
C

Cptkid570

Ensign
Joined
Oct 18, 2005
Messages
967
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

That's it! Vapor Lock.. Thank you!

Anyway, if it's vapor lock, then wouldn't the engine run fine once everything cooled back down? I guess if he is having this problem right away (while everything is still cool) then it wouldn't be that.
 
subcrx

subcrx

Petty Officer 2nd Class
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Sep 3, 2007
Messages
197
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

do you smell anything funny when it does this?
 
H

HighLineCBR

Petty Officer 2nd Class
Joined
Jul 6, 2008
Messages
104
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

Vapor Lock??? Hmmm.... that actually sounds like it could be it. The boat seems to run fine for few good minutes when cool. Once its warms up it starts to have the problem constantly.

My fuel line from the pump to the carb runs along the engine block, so it definately gets real warm.

I will test this on Sunday as well.
 
C

Cptkid570

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Oct 18, 2005
Messages
967
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

Highline - I wanted your opinion on the 23' Donzi Ragazza -- you can email me at cptkid570@aol.com or just post it in here. I was wondering if you have enough cabin space, is there a sink, and if the porta pottie is in a separate compartment or under the vberth cushion. Also, (when working) how is the performance?

I've considered buying one at times... have to sell my current boat first though (looking to go from a 26' boat to something more in the 23 to 24' range)
 
H

HighLineCBR

Petty Officer 2nd Class
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Jul 6, 2008
Messages
104
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE - SOLVED!

Re: 350 Chev OMC Loosing power at high RPMs - UPDATE - SOLVED!

So I went to the lake yesterday and took a 5 gallon gas can with me. Once i ran the boat from the portable gas can it ran like a clock! No choking.

It?s always something stupid that causes problems. But at least now I have a new carburetor, pump and fuel lines.

I will replace the fuel pickup line this week and hopefully this will solve the problem once and for all. I have a feeling it?s completely corroded. We'll see


Thanks for all your input guys!
 
U

Uraijit

Banned
Joined
Feb 5, 2008
Messages
884
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

Check your anti-siphon valve while you're at it.

Glad you found the source of your troubles.
 
H

HighLineCBR

Petty Officer 2nd Class
Joined
Jul 6, 2008
Messages
104
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

Cptkid570 said:
Highline - I wanted your opinion on the 23' Donzi Ragazza -- you can email me at cptkid570@aol.com or just post it in here. I was wondering if you have enough cabin space, is there a sink, and if the porta pottie is in a separate compartment or under the vberth cushion. Also, (when working) how is the performance?
Click to expand...


I?m not sure how the original set up on the Donzi Ragazza 23' is. My interior was completely redone but im guessing it's close to the original format. I do not have a porta pottie, but I guess I could install one under the vberth cushion if I wanted to.

There is a sink, which is located under the glove box. I disconnected mine and converted it into extra storage. I do not have a need for a sink. But it would be nice to have a pull out shower to rinse off.

The cabin space is roomy for a 23 cuddy. I actually went camping over Labor Day weekend and slept on the boat for 4 nights. It is very comfortable and plenty of room.

Performance is great for this type of boat. At times I wish it had a bit more power but once I remind myself of the latest gas prices I am more than happy with the performance of my boat.

Let me know if you have further questions.

Thanks,
 
C

Cptkid570

Ensign
Joined
Oct 18, 2005
Messages
967
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

Thank you for the info. I'm glad you found your problem!
 
H

HighLineCBR

Petty Officer 2nd Class
Joined
Jul 6, 2008
Messages
104
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

I took out the fuel pickup tube last night and found it to be completely clogged. I couldn?t even blow air through it. Turns out it was clogged with not so much of the "usual" crap but a long piece of Teflon tape. Not sure how it got there, my only explanation is that the previous owner must have dropped it is the tank by accident and it got sucked up.

I've also added a clear inline filter and should be good to go for quite some time. Only too bad the season is coming to an end.

I learned my lesson with this. With this type of problem I should have started my search from the tank to the engine. I started with the Carb and worked my way to the tank, replacing everything along the way...

thanks again for the help guys, and I hope this thread helps others.
 
B

boat anon

Cadet
Joined
Jul 26, 2010
Messages
24
Re: 350 Chev OMC Loosing power at high RPMs - UPDATE

i am having a similar problem...have a mercruise 260 (gm350 5.7 on an '87 with alpha one outdrive.) i am using an auxillary 12 gallon tank brand new, new filter, new fuel pump, new 1409 edelbrock carb.

as soon as i hit 3000RPMs, the RPMs cut, and revs back to 3000, and cuts again. (sounds like someone reving a car and letting off the pedal every other second) as long as i hold the throttle at that level it will happen repeatedly, anything under that the engine runs fine. good compression, good water flow, even replaced my distributor and plugs about a month ago. everything is new and im giving up. any suggestions would be highly appreciated! btw this is not under load, this happens with muffs too.
 
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