I am a new guy here, have a 35hp stock mud buddy on a 3 man gator hide
been out a couple of times with the boat since I purchased it two months ago, have had an absolute blast with it

run the motor every couple of weeks to keep things charged and running

last night I went to start it, but first I disengaged the trailering lock pin, and let the motor down
went to start it and starter would make a half turn, then bounce back, tried it a couple of times and it seemed like the motor had a hydro lock on it,
put the motor back up on the locking pin, after a few minutes it turned over fine and ran great

lowered it while running, and started to back fire at higher rpms.

could the oil somehow be causing a hydro lock in the engine?

when tilted down the oil level reads full, when the engine is level it reads less than full on the stick

5W30 mobile one synthetic

Could be the float tab is a bit out of adjustment. That will fill up a cylinder with gas. Make sure u dont have gas in the oil. Also make sur tank is vented good

found the problem yesterday, started it and only had one head generating heat, shut it down pulled the plug and the top of the plug was squished, some porcelain knocked off.
so I stripped down the motor, took off that side head , found out in disassembly that the muffler is toast, all loose inside
something must have fell inside the head and busted the plug
the head inside looked good, so the piece must have exited the exhaust port.
just waiting on a head gasket and will re assemble this week . need a new muffler will get a SS model
lucky no scoring inside the cylinder wall, everything looked good inside.

Glad u found it. While the head is off at least check the valves for leaks or you might put head back on for nothing.

You know they're leakin'

leak a bit, it will fly. Leak alot or bent. At least u will have practice for the next time

finally had a chance to put it all back together yesterday, a slip up at the local shop had me waiting 2 weeks extra for a head gasket
also put a new SS exhaust on it, new gaskets,
fired it up and all seems good to go. will have to wait til the weekend to get it on the water and give it a tryout.

all in all a fun job to do