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New problem, WOT bog/surge

1456 Views 3 Replies 4 Participants Last post by  RSCHAP1
Let me clarify when im pushing 4500-5000 rpm I lose power and then it comes right back, but its very intermittend. at first thought it was carb so I rebuilt it, and it was running awesome, and then all the sudden it started doing it again. I have a hunch it may be the IGN Module (thunderboltIV), but would like to test it to be sure, because a new one of those badboys is now 350.00 bones. Thats a very expensive part swap. Any help would be great.

What Ive done so far...
Rebuild carb-Quadrabog stock
Changed fuel filter water seperator
Found vent tube from fuel pump to carb clogged so I cleaned that out.
Replace plugs, wires, cap, rotor

So that where I'm at, done preety much everything fuel side, except fuel pump, but boat runs good, and starts good, and fuel press is good and consistent even when it bogs, that what got me thinking its on the ignition side. Thanks Guys........
1 - 4 of 4 Posts
There really is no way to test it for that issue. In Mercruisers eyes its either good or its bad.
check all your fuel lines for tight fittings and or cracks. My buddy went through the same thing until they found a crack in his fuel line started to suck air at WOT no power or top end sounds a bit like your situation and it is easy fix if you find a bad one. Unforunately he did all the things you mentioned first also :(
Spray brake cleaner or similar all around intake. Where intake meets heads, carb base etc. Change in rpms will tell you if there's a leak in those areas...Helped me find a few leaks before. Good Luck
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