5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HELP

[FishnFreak75]

Just bought an 1988 Seebold Eagle with 5.7 Mercruiser 350. It runs ok but has no bottom end power and takes forever to plane off. When it finally does it porpoises really bad if I try to trim up. This is my first i/o and not sure where to start. Thank you

 

[Bt Doctur]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

Well, what else have you done to it? some hull pics of the bottom, it might be "hooked" causing the porpoising. All filters, full tune up, good fuel, timing, sparkplug firing order, to name a few things to do.

 

[FishnFreak75]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

Well, what else have you done to it? some hull pics of the bottom, it might be "hooked" causing the porpoising. All filters, full tune up, good fuel, timing, sparkplug firing order, to name a few things to do.

I havent made any changes to the boat since I bought it. Sorry, dont know what "hooked" is. Engine sounds like it is running ok, but lacking rpm's maybe. In nuetral revs beautifully.

 

[Bt Doctur]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

your mechanical ability on a scale of 1-10?

 

[FishnFreak75]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

your mechanical ability on a scale of 1-10?

Prob an 8.

 

[Bondo]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

I havent made any changes to the boat since I bought it. Sorry, dont know what "hooked" is. Engine sounds like it is running ok, but lacking rpm's maybe. In nuetral revs beautifully.

Ayuh,... Welcome Aboard,... Hold a straight edge against the keel line on the bottom of the hull,...

It should be Straight for the last 4 to 6',...

If ya see daylight under the bar, that's a Hook,...
If the bar rocks over a hump, that's a Rocker,...

Revin' in neutral is irrelevant,...
Do a compression test, 'n tune up,...

What prop pitch, 'n blade design is on it,..??
What rpms is it runnin' at Wot,..??

 

[FishnFreak75]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

Thanks for the help, Prop is a Precision Perf Turbo three blade 14.5x22. Wot is 4000 rpms at 50mph.

 

[stonyloam]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

Sounds like some trim tabs might be of help.

 

[Bondo]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

Thanks for the help, Prop is a Precision Perf Turbo three blade 14.5x22. Wot is 4000 rpms at 50mph.

Ayuh,... Yer Way over proped,... Ya oughta be seein' 4600/ 4800 rpms, at Wot,...

Or yer motor ain't makin' the power it did,...
hence a tune up, 'n compression test is in order,...

 

[FishnFreak75]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

What prop do you recommend?

 

[Bondo]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

What prop do you recommend?

Ayuh,... I'd recommend ya get the Motor up to snuff, 'n then worry 'bout the prop,....

I see ya got a thread in the Prop Forum,... you'll get the prop info ya need there,...

 

[FishnFreak75]

Re: 5.7 Mercruiser, No bottom end power, throttle sluggish, horrible porpoising HEL

Ok, thank you