SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: patha on June 01, 2009, 09:16:29 PM
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Boat ran great all day and then between a stop and going again it was hard to start backfiring and sputtering. Won't idle below 1500 or 1600. Idle screw has no affect as it won't stay at 1000 RPMs. What could the problem be?
Got it to kinda run but it would idle at 2000 or so for a few minutes and then drop drop and stall out. Runs good above 2k.
ANy ideas before I start messing with the carb and idle settings...I found a post on here with instructions for it.
It's a Holly 750 DP on a Ford 460.
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Boat ran great all day and then between a stop and going again it was hard to start backfiring and sputtering. Won't idle below 1500 or 1600. Idle screw has no affect as it won't stay at 1000 RPMs. What could the problem be?
Got it to kinda run but it would idle at 2000 or so for a few minutes and then drop drop and stall out. Runs good above 2k.
ANy ideas before I start messing with the carb and idle settings...I found a post on here with instructions for it.
It's a Holly 750 DP on a Ford 460.
I will take a blind shot at it, either a sucked carb to manifold gasket or possibly an intake gasket.....
Otherwise the carb has a hairball in it :P
You don't live in Morgan Hill do you? (My nieghbor was running his boat in his backyard the other day and it sounded just like you describe) :-\
GT
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You mean the gasket could be shot and there is a vacuum leak?
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You mean the gasket could be shot and there is a vacuum leak?
Yup!
A cheat would be to spray a bit of WD40 around tha base of the carb an manifold while she's running, when/if you find the rpm stabilize, you found your leak. 8)
GT
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Will try tomorrow. Don't think the neighbors would enjoy the motor starting up right about now.
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I always used starting fluid to check for a leak, if the RPM's go up, well it's sucking in the fluid ;)
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It only takes a few minute to pull the carb off and the gaskets are pretty cheap...replace anyways. cheap insurance!
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Throw a power valve in there too
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Check your ignition timing as well. Might have a little effect on this, but the 460 likes between 10 and 13 degrees in my experience. (can be kinda hard to do this, as most marine engines have dampners from different years, etc.)
Best , and easiest, way to find true TDC on a 460, rotate the engine backwards (Tighteneing the crank bolt) until #1 is coming up on compression stroke, when at TDC, mark the dampner with a silver sharpie. rotate over again but watch #6 and when it starts to go down, mark it again. that should be 10 degrees BTC.
Also a good way to find out if your dampner/timing indicator are even remotely close.
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turns out i towed the boat home from the river for a $2 rubber vacuum cap.
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That sucks! Glad you got it figured out though!