Loss of power over 3000rpm

[brpesa]

Hi
I have 1988 27' luhrs with 350 chevy PCM, borg warner tranny and straight shaft. Up to 3000 rpm runs good but when i push the throttle over 3100 rpm toward WOT engine losing power and boat slowing down instead getting faster.
On 3000 rpm boat speed is 10-11 knots which is not fast enough i should get at least 13-14 knots cruising speed.
What could be wrong with an engine that make it dies down and how can i know if i have correct prop, because somebody told me check the prop if i change it i might get on speed.
Thanks for help

 

[Bondo]

Re: Loss of power over 3000rpm

Ayuh,... Sounds like Water in the fuel,.... Check the Contents of the fuel filter,....

 

[brpesa]

Re: Loss of power over 3000rpm

Thanks I will replace fuel filter first.

 

[Bondo]

Re: Loss of power over 3000rpm

Thanks I will replace fuel filter first.

Ayuh,... That's fine, but inspect the Contents of the take off filter for Crud, 'n Water,...

 

[brpesa]

Re: Loss of power over 3000rpm

Ayuh,... That's fine, but inspect the Contents of the take off filter for Crud, 'n Water,...

I replace fuel filter today and take boat for a ride but didn't change much.
In filter I didnt see no water just a little dirt.
I think must be some issues with carburetor.

 

[brpesa]

Re: Loss of power over 3000rpm

https://www.youtube.com/watch?v=6sTHaJwPsAU

here is the link to the video what is going on

 

[Bondo]

Re: Loss of power over 3000rpm

I replace fuel filter today and take boat for a ride but didn't change much.
In filter I didnt see no water just a little dirt.
I think must be some issues with carburetor.

Ayuh,.... I think yer probably right,...

A diagnostic Tune Up, might point ya in the right direction,....

 

[redneck joe]

Re: Loss of power over 3000rpm

seafom is my best friend.

 

[278 Vista]

Re: Loss of power over 3000rpm

Awsome video. By seeing that, I guarantee its not an ignition problem. Your engine isn't breathing properly. I'd go with a full strength blast of Sea Foam too. Next, I'd replace the neoprene fuel lines. After that a fuel pump volume and pressure test are in order. Keep us posted please.

 

[brpesa]

Re: Loss of power over 3000rpm

Awsome video. By seeing that, I guarantee its not an ignition problem. Your engine isn't breathing properly. I'd go with a full strength blast of Sea Foam too. Next, I'd replace the neoprene fuel lines. After that a fuel pump volume and pressure test are in order. Keep us posted please.

What is the Sea Foam ?

 

[Bondo]

Re: Loss of power over 3000rpm

What is the Sea Foam ?

Ayuh,.... In this case, Google is yer friend,...

 

[brpesa]

Re: Loss of power over 3000rpm

Ayuh,.... In this case, Google is yer friend,...

interesting..... i don't know how i didn't hear about it before.
Will grab me a bottle tommorrow.

 

[Silverton34c]

Re: Loss of power over 3000rpm

interesting..... i don't know how i didn't hear about it before.
Will grab me a bottle tommorrow.

See if the 4 barrel is opening up...sounds like the 2 barrel is working and dying when the 4 barrel should be kicking in...would cause the same problem you are experiencing

 

[Capt Ken]

Re: Loss of power over 3000rpm

Something I've run into years past with inboards. The inner liner of the exhaust hose can tear and at a certain RPM, it will balloon out and block the exhaust causing too much back pressure. Had a Penn Yan drive me crazy years ago.