89 7.4 Bravo only hitting 4000 WOT

[stinger222]

just bought it last month, 2550 Chap 2550 SX, 5000lb boat, 23 pitch Mirage prop. Boat has been upgraded to GM Rect port heads, matching intake. still has stock Qjet carb.

Runs great otherwise, but I am thinking top end would be better. Prev owner says the Qjet is holding it back, 800 cfm holley will hit 5000 rpm. Not sure what the issue here is.

 

[jerryjerry05]

Re: 89 7.4 Bravo only hitting 4000 WOT

If you are doing 4000rpm at WOT.Then you need to go down in pitch from a 23p to a 21p maybe a 19p. Unless the motor is bogging down.That quad/jet has been working fine on millions of boats.Jerry

 

[stinger222]

Re: 89 7.4 Bravo only hitting 4000 WOT

I spk with previous owner today and he said the prop was tweaked to more like a 26 pitch...I guess that explains why I am only hitting 4000rpm. I have a spare 20 pitch that I'll throw on there and see where it lands WOT.

 

[stinger222]

Re: 89 7.4 Bravo only hitting 4000 WOT

put on the 20 pitch today, as expected I am getting 5000 rpm at WOT. Boat feels a lot faster as well. Speedo not hooked up so I can't tell. I think a 22 pitch would be right on. Anybody else agree?