4.3 poor performance...?

[sirfoulsalot]

Hello Everyone,
I have a 1996 Cobia 188 (18') bowrider.
Volvo Penta 4.3 160hp..rebuilt last year because of hydrolock
1.85 Gear Ratio
2,200 Dry Weight
3/4 tank of gas
Quicksilver Hydrofoil
New Michigan Match Aluminum 14x19 prop..

Out on the lake the other day (alone) with the GPS, I'm going 36 mph WOT at about 4,200 RPM. I'm not 100% sure, but I believe I had a 21' prop on it for a little bit last year and still had the same issue. I just thought this was as fast as this boat was supposed to go until I started looking on here and noticed my boat should be going at least around 45mph. When I'm at WOT the motor really does sound maxed out. It sounds like it is revving pretty high..(like at peak RPM). I will admit my Tach might not be completely accurate as well.(it shows I am idling at 10,000..I know I'm not idling that high.) Which really makes the 4,200 at WOT even worse!
I have done a little research on here, including the sticky on diagnosing low WOT in the i/o forum. I guess the first thing to check would be the fuel system. That may be a little over my head, and I'm trying to avoid a mechanic unless it is necessary.
Any idea's?
Any and all help/advice is greatly appreciated.
Thanks,
Randy

 

[hwsiii]

Re: 4.3 poor performance...?

Randy the first thing you need to do is chek your tachometer. Iy is a pretty safe bet that it is not working right, and without that correct information I certainly can't help you. Sorry.

H

 

[strocker383ca]

Re: 4.3 poor performance...?

first thing to fix is your tach... after check your ignition timing if the motor doesnt look to have power check maybe someone put the timing retard on it ... its the heart of the motor ...

 

[sirfoulsalot]

Re: 4.3 poor performance...?

Thanks for the help!
I will check out the Tach first and go from there. I will also update what I find out.
Randy

 

[hwsiii]

Re: 4.3 poor performance...?

Randy, that will be great, let us know.

H