Engine just flutters and pops.

[Jerome Lowery]

My grandson has a 1972 Slickcraft, 188(302). Runs great for a while. Then out of the clear blue sky, it will pop, studder and carry on. Sometimes it just quits. Removed engine cover for a few minutes, sometime it runs great again, and then not so great. We are going to convert to pointless distributor. Will be checking carb, fuel pump etc. I can troubleshoot old school automotive engines no problem. Is there anything I need to do or need to know about marine engines? Going to change the thermostat for routine maintenance. I can't find what heat range to use. Any and all information will be appreciated.
Thank you....

 

[NHGuy]

Chase through the fuel delivery system. Dump the fuel separator and filter contents into clear containers to check for junk. Pop means lean. You should not heavily load the engine when it's popping or it could melt a piston.
Check for float setting and needle/seat condition. Carburetor condition...like a big ol american car!
It's old so see if it has mechanical timing advance, if it has make sure the mechanism is not stuck.

 

[Jerome Lowery]

Thanks, that's the 1st thing we will check. It has a Holly 2 barrel on it. My hotrod has 2 Holly 4 barrels on it, so I really know how to check and tune a Holly. 1 question. Do you think the mechanical advance could be sticking? I think it wouldn't do that only when it warms up. Thank you for the input. Appreciate it.

 

[Jerome Lowery]

Removed thermostat housing. No thermostat! Removed distributor cap. Does not have a vacuum advance. Does not seem to have a mechanical advance. Looks as if the plate is mounted solid. Never saw anything like it. I thought the timing needs to advance as RPM increases. I'm so confused. There is a spot for the thermostat, but empty. Do you need the thermostat?