Ignition Problem?????
502 Mag 91' 242LS model stock,got a bad shutter under power started hearing strange pop not like a backfire and not thru Carb but sounded from in the motor itself. Couldnt tell anything unusual @ idle, no overheat, oil pressure good, just when I try to plane,motor shutters and makes this poppng noise. Ordered all new ignition parts less coil reckon this is good start. Only had boat since last June, never missed ever, Please dont let this be catatrophic right at the start of this good weather......... any other sugestions as to where and what else I should keep my eye on wondering bout the timing possibility it jumped? Engine fires on first turn still and idle to my best guess still normal, but this past weekend wanted to shut of while idleing round docking area but it cleared. Didnt think much more about it till now. Havent got to do anything in depth yet parts will be in Wendsday.... This probably dosen't sound like much but ....... HELP
Posted in Tech sight havent gotten lot of response figure I m heading in some direction anyway. Man this is driving me nuts I need my @#$% parts so I can figure out this BS

It might be a lean misfire ( the pop). Straving for fuel may be an answer. On your fuel tank, there is a fitting which screws into the tank. If you remove the fuel line and then the fitting, you will find a check ball. Look for an obstruction either there or in the pick up tube. You can clear the checkball or take a punch and drive it out with the spring. It is only there to prevent the fuel from running back into the tank from the carb. This makes it easier to start. Just a guess but you never know!
Dave (AXA)

That strange popping noise sounds like a valve to me not ignition.Is it constant and does it increase with RPM? If so better pull vave covers and check springs or push rods. MFB

Thanks, I ll be looking in all directions..... Waiting patiently (tapping foot) , for parts to come in, supposed to be now. Taking off as soon as they are in hand. Taking compression gage also. fingers crossed.

I agree with 357. It sounds like a possible broke valve spring or maybe a wiped cam lobe. While your waiting on the ignition parts, I'd pull the valve covers off and roll the motor over and check things out.

Well, the " just know enough to be dangerous... tune up" didn't fix the problem. Dropped boat off at shop this A.M., sittin here in a daze figuring how much this summer boat f.u. is gonna cost Wondering now.... hummm.. is it bad enough to talk my wife into "The it really needs a blower speach."

Had similar problem. Mine was a blown headgasket. Caused valve to bend pushrod. Check oil. if coffee colored already blown.
Also lack of oil changes could cause rocker to wear out. As recommended before, best to pull valve covers and check for build up or worn rockers.
It is hard to find a blown head gasket because raw water cooled, doesn't overheat. My engine idled fine but couldn't get over 1000 rpm @ it's worst.
Sorry
Happy Captain Bob

Much worse than a head gasket, Lost a couple of lobes on cam! Total rebuild, scarred up 8 JE 700 pistons and lost cam but block cleaned up with hone job, saved crank also all was not lost...... but most! what a great time to free up some flow on those heads huh!!! gotta laugh to keep from cryin!!! F&%$ summer! aint no fun without my boat, I belive Ive started a dependency problem
Rocket

OK so now your hooked-- WELCOME TO THE CLUB.

Damn, that's too bad. Did they say what they think caused it?