Engine RPM
 

I have a 1982 302 Formula with TRS drives Borg warner trannys and 468 cu. in. chevs running about 420 HP ( the original 330 motors bored ,re cammed, bigger valves etc). I am spinning 25 pitch props and can't seem to get the motors to rev over 4100 rpm. Is there a rev limiter I can adjust. On the GPS I'm getting 60 MPH with these stats. I tried 21 pitch props cupped to 23 and got more RPM and less speed . I would love some imput. Thanks Rick G.

that is a pretty heavy boat so the speed don't seem too far out of line.

as for the rpms that doe sseem low. Try smaller props to bring the rpms up. Maybe 4 or 5 blade mighthelp. I know i tried 5 blade and they hook up an slip WAY less than the 3 blades. I lost 1000rpms but actually gained 2 mph. Now i just need to get the right pitch and i'll be set.

try the mec 4 blades (i forgot the anme, but its not the bravo 1) MBAM love sthema nd recomends them for eveyone to try.

I have a similar setup Rick and for reference purposes: I run twin 330hp 454s bored to 468s with comp cam, rect port heads, crappy exhaust manifolds with imco risers (thru-hull). This is in a 1988 30' scarab panther. I get 68.1 with 25p mirages (non-plus) at 5000rpm. With 27p mirage plus I get 4500 rpm and 66.0 gps, but have a much better cruise speed.

You are definately low on speed and rpm. Things I would look at are: Is the throttle plate(s) open fully, depending on carb..... is the air valve opening correctly, what do the spark plugs look like, is the bottom clean, and are you trimming properly?

BT :cool:

BT The boat was painted last winter and is kept clean. I will pull the plugs this weekend. I agree I think my problems may be carb related. Possibly the timing may be abit retarded. I will let you know what this brings. Thanks Rick G.

if you have a different cam, you need different jetting too. make sure you are not extremely lean and about to burn holes in them pistons

I think that is part of my problem I had the carbs fattened up but I think I may have gone too far. Rick G.