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8-9 pounds of fuel pressure is at idle, std HP carb fuel pump driven water pump pulley. My 96 2nd are huge & I even thought something was wrong, but thats kinda got me in ball park at full throttle. I chose the Merlin intake over dart as it was freely available right then & it had the bronze water jacket. I started off with stock jetting...way lean & it was just easier to get a base jetting by going pri/sec. I can fine tune it later. My hull is (24 Outlaw) very inefficient when it come to speed. So maybe it needs the bigger sec. to meet its fuel needs. I should have gone with 741 cam, the 731 is not that much of an improvement on stock. I wanted to be easy on the valve train. I just ordered a new set CMI headers today as my old set cracked in the collector area. I will try it this weekend again. I have about 25 hours on the motor incl. a Poker Run.
John

"I should have gone with 741 cam, the 731 is not that much of an improvement on stock. "

I'm not to sure if I would agree with that.;) If we are comparing stock hp500's with mild head work and the stock ignition.

I took a vacation day yesterday and went boating. Tried more jetting set ups. The motors are running very strong and responsive up to about three-quarter throttle. But she still seems flat when you give it the rest of the throttle and the plugs still show pretty white after a high speed run. Richening the jets has helped the low and midrange performance but has not affected the top end at all (up or down). I am really wondering if the fuel pumps have slowly gone away and are not delivering enough gas once the motors are up in the rpm range. I was going to hook up fuel pressure guages but had to scrap that plan yesterday. The allen head pipe plugs in the fuel line where the guage would connect were so tight that I was worried the hex bit wrench was going to strip them out. I didn't want to waste the day screwing aroung with that. I will figure out a way to rig the guages before I go out next time.

I have had boats in the past that lost top end speed, but otherwise ran normally. Changed the fuel filter as most people would suggest and it made no difference. Then put on a new fuel pump and the motor came back to life and the top end was there again. The pumps must gradually lose output (my guess would be somewhere either side of 200 hours). At some point the pump can not supply enough fuel at WOT, but the motor runs fine everywhere else. This would explain why putting in bigger jets won't help or hurt the top end - the motor is using as much fuel as the pump is putting out.

Does anyone have any thoughts on this?

"The allen head pipe plugs in the fuel line where the guage would connect were so tight that I was worried the hex bit wrench was going to strip them out. I didn't want to waste the day screwing aroung with that. I will figure out a way to rig the guages before I go out next time."




I have two stripped out plugs and two gauges still in the box:crazy:

Another winter thing!

Do you still have the anti-syphon check valve in you fuel line?

Yes, the fuel system is totally stock. I should double check, but I presume the anti-syphon valves are still in place. Boat is a 1999 and had 110 hours on it when I bought it used.

Those anti syphon valves are killing fuel pressure for sure. I pulled mine out and tried to blow thru them and was amazed at the restriction they caused, plus my motor starts with a flick of the ignition.

Where are the valves located?