Re: No more power past 3/4 Throttle
 

I did a plug reading at 4k which puts me just into the secondaries and the plugs were very lean. that was 80 front 82 back. So I upped to 82 front 84 back that worked good at 4k. I have not taken a reading at WOT yet I'm going to check that this weekend. Transom is clean though so I don't think I would be that rich.

Re: No more power past 3/4 Throttle
 

I'm running a -8 from the pump to the carb. Gauge is at the pump. I am running in line fuel filters by earls. They are after the gauge. I could try to move the senders up by the carbs to make sure I'm getting it up there. or take the filers out for a run.

A plug reading this weekend should tell me if I have a fuel problem. It does make sense. Especially the jet changes with no rpm or mph changes.

Re: No more power past 3/4 Throttle
 

Not sure if this will help but I had a 31 with 502's, hyd roller, dart int, stock heads with bowl blend, 800 carb, gill exh with a 4 1/2 tail pipe and ran 79 on GPS with 25 Mirage wheels at 5450. I figured the motors made 450hp or so. 27's ran 82 at 5200.

Re: No more power past 3/4 Throttle
 

Bob that does help. It helps me realize something is definatly wrong... What kind of 31. How much did it weigh.. I know this boat of mine should go deep in the 70's if not the low 80's.

Re: No more power past 3/4 Throttle
 

Are the carbs in box stock configuration? An 850 on a 502 should be real close the way it comes from Holley. If it isn't in stock configuration I would put it back and start over from ground zero. Have you tried to run the motors without the flame arrestors just to see if it makes a difference? I also wonder what a single plane manifold would do compared to the air gap on this motor, particularly over 5000 RPM. The headers are still your biggest problem.

Re: No more power past 3/4 Throttle
 

Vette I started from box stock. They ran good but it was lean.. So I started upping jets 2 sizes at a time 82's up front are good. I have not made a plug reading at WOT but I have stepped up from 78's in the rear all the way to 86's and there has been no change in rpm or speed. That and some of the responses on this thread are leaning me toward poor fuel delivery. I am going to yank the fuel filters this weekend. That will make my gauges more accurate. Currently my gauges are before some inline fuel filters I added. I am thinking they could be restricting flow. I also will be taking a WOT plug reading.

I agree manifolds are killing me but I think I still should see at least md 70's even with those manifolds.

As soon as I scrape up 5 grand I will replace them... Problem is they have to be custom made. so cost is crazy...

Re: No more power past 3/4 Throttle
 

Leathl I had a 31 Sutphen around 7500-8000#.

Re: No more power past 3/4 Throttle
 

I had mine on the scale with me in it and half tank of fuel it was 7200...