I have a 86 400 Scarab with twin gen 4 bbc .40 over 177 blowers stainless exhaust with 950 Holleys. 94 jets in front with 6.5 power valves , 98 in the rear no power valve. Holley 130 mechinacial fuel pumps and 3/8 fuel line, PSI set at 7

When I am cruising at 3000 boat will surge and sometimes pop. I back out of throttles motors will idle fine the a few seconds later when cruising again it will surge like it is running out of fuel. So back to the the dock I went. Any ideas

Thanks for the help

Steve

if you are not boost referenced the 6.5 power valve is your problem,or one of them.

Mike - can you elaborate? I am chasing a low power problem on my 540/250 combo but only on one engine. I am a running Nickerson 1050's with 98's in the front and rear with a 6.5 PV. AFR's on all banks are in the 10.5 range (plenty rich) at 3Kish but the port doesn't want to rev any more... Sorry for the thread high jack.

Do you think should go bigger or smaller. I had the 8.5 in before the 6.5 PV. Does the same thing with either ones. I

Thank you for your time,

Steve Vasquez



QUOTE=mike tkach;3987285]if you are not boost referenced the 6.5 power valve is your problem,or one of them.[/QUOTE]

most non referenced engines work best qith 10.5 or 9.5 pv,you may have other problems.

10.5 afr at part throttle is way to rich and robbing a lot of power,are you diluting the oil with fuel quickly?

I have a almost the same set up. I have a 24 Scarab with a blown 489. Small 174 blower. Dean did my 850. Its now flowing about 920. I have 4.5 pv front and rear. My jetting is 90/91 front and 92 rear. I run 7psi fuel pressure and my plugs look great. .I'm a hair under 80mph. Check you air bleeds. Check to see if your anti siphon valve from you tank is good (if you have one). I had one go bad on our express cruiser.