Im scratching my head here trying to figure out why this thing wont pull the RPM's. Ive read through most of the posts on Timing and Advance trying to get some clarification and understanding what I am looking at, but still find myself wanting to ask questions to get a better understanding of what to check and adjust.
What I do know:
90' 20.5 Carrera Elite
Edelbrock Hi-Rise Manifold
750cfm Holley Marine - Rebuilt, had a TON of corrosion
Mallory ProComp 9000 Megnetic Breakerless Ignition (Mechanical Adv)- New
Mallory Coil - New
Pump Super Gas
New AC Delco MR43T's
No Leaks, just got done cleaning up corrosion on exhaust manifold and resealing
12JG Pump completely rebuilt with new split bowl, new shaft, new Impeller by Dan at Jett Marine Performance. He said he cut the imeller back and put an A/B cut on it.
Everything is fresh, but its only turning 4500 RPM.
We went to checking the timing this weekend, but forgot to grab some timing tape, but we decided to at least check it anyway.
It fires up with a little pump/help from the throttle, and idles at 900rpm on the water. When we hit it with the timing light, it was a solid 8 degrees BTDC. Because the timing marks only go to 16 on the plate, we really couldnt get an accurate reading, but at 2000rpm, it was about 3/4" past the 16 degree mark. When I spoke with Dan, he said it should be pulling a solid 4600-4800 rpm's with bone stock motor with the cut he put on the impeller. So now its down to trying to figure out why this thing wont pull the RPM's. We pulled the plugs. They look good, they arent brown or black.
So now its down to timing and advance, or there is still some crap in the carb. This carb appears to have had a bunch of custom work done to it by JP Marine. I bought this boat in Huntington Beach, CA, if that makes a difference. Im not trying to factor in the MPH here, but its only pulling 51mph on GPS with a place diverter, when it should be 55-58mph.
My cousin has 20.5' Eliminator Daycruiser with a 454bbc 2-bolt, 600cfm holley, no hi-rise intake, and completely stock pump from 1988 w/o a diverter and he's pulling 4700rpm and 52mph.
Nevertheless, something still isnt right, and I already have enough gray hair...
So should I be looking at the timing and advance, or looking back into the carb, or both?
Thanks in Advance