Engine backfired and now won’t start

[Jb44]

Hi all,
I have an 83 Sea Ray with an MCM120 2.5L and a first gen alpha one drive. I rebuilt the carb on day one and the boat would run great on muffs and would stay running in forward gear. On the water it would idle fine but would die with a bit of throttle in forward gear. I replaced the lower shift cable as it was corroded and seemed to be a glaring issue. Fast forward to everything hooked back up and adjusted. I start up the engine on muffs and put into forward gear and the boat seems to backfire out of the carb with plume of white smoke. I try again and have the same problem. I disconnected all cables and now I cannot get the engine to start at all. When I do crank it seems sluggish and now there seems to be a huge drain on my battery as it is brand new and has died twice after a charge in two days as I’m trying to get it started. Was it a bound up outdrive, did I uncover another issue by coincidence? Im really stuck on this one and hope someone may have some insight!

 

[kenny nunez]

Remove the spark plugs to check if there is water getting into the engine.
Try turning it over next.

 

[Bondo]

Ayuh,..... Welcome Aboard,..... Back-firin' through the carb, says it's lean, not gettin' enough gas,.....

The slow turn over while crankin' on the starter, is most likely corroded cables or their connections,....

If you think the drive is draggin', pull the drive, 'n try it,....

 

[Jb44]

Kenny, gonna go ahead with a compression test to rule out head gasket issues so I’ll check for water then. Bondo, thanks for the insight. I’ll pull the drive to rule out a binding issue and then go through the fuel system. Thanks for the quick replies y’all!

 

[Eric 3.7LX Alpha 1]

How old is the gas your using in the tank.

 

[Jb44]

Update time,
Eric, gas looks to be in good shape but not 100% sure on age. I’ll likely change it, just need to figure out where to take 30 gallons of it. So compression looks good and no water coming from the cylinders. New battery keeps the engine cranking for a lot longer but bad starter still isn’t ruled out. I found out if I remove any single spark plug the motor will start and run (rough obviously) anyone got any experience with this? Thank you all for the replies so far!

 

[Jb44]

Update,
Took the shift cables off and opened the throttle a bit with all plugs in. Starts right up. Looks like a carb adjustment is in order.

 

[Bifflefan]

I am not sure what ignition you have, but if its points I'd replace them and the condenser. Your issue sounds exactly like they have reached their useful end.