rpm issue 350 gm

[kmadden1]

Hi,

Have a 350 gm and here is my problem. Last year ran around 4500 rpm at WOT, start of this year about 3600 and last trip was 2700. Thought this would be possibly a flapper problem in the exhaust, checked that and all looks well which I beleive I should have known as quick burst in neutral would run up to 5000 which i think would not be possible with an exhaust blockage. It is a 4bbl rochester carb and it is drowing with gas at wot so i'm pretty sure it is not a fuel blockage. Any ideas that I can try? oh yeah same size prop trhoughout all of this, 14.5 19 pitch although between last year and this year did switch to an SS from aluminum.

Thanks,
Kevin

 

[Gary H NC]

Re: rpm issue 350 gm

Revving the engine out of gear tells you nothing...It could be running on half the cylinders and still hit 5000 rpms...

How long since a full tune up and compression test??
Drowning with gas?? explain that please...

 

[kmadden1]

Re: rpm issue 350 gm

Revving the engine out of gear tells you nothing...It could be running on half the cylinders and still hit 5000 rpms...

How long since a full tune up and compression test??
Drowning with gas?? explain that please...

Tune- up a month ago Compression check on all cyls was great, seems to be hitting on all cylinders as at 2000 rpms all is well and just about where it used to be for speed etc. Basically on the gas front way more in the carb than i have seen it in the past.
Thanks!

 

[searay3]

Re: rpm issue 350 gm

If its flooding, time to pull the carb. Did the tuneup include all fuel filters in your system? Try running a remote tank plumbed to the suction side of the pump. Maybe it's not pulling fuel out of the tank as it should. Is this merc. volvo, omc??

 

[kmadden1]

Re: rpm issue 350 gm

Thanks, all the filters have been replaced, but I will try that again. and next i will try pulling the carb. If anyone thinks of anything else please let me know

 

[45Auto]

Re: rpm issue 350 gm

Did you actually do a compression and/or leakdown check, or did someone just say "the compression feels great!"?

If the test was done, do you have the numbers?

 

[kmadden1]

Re: rpm issue 350 gm

I checked the compression when I did the spark plug change ... betwwen 152 and 160 psi all eight.

 

[kmadden1]

Re: rpm issue 350 gm

OK that is great i will check the advance!

1989 and it is a Yamaha 260 hp