All of a sudden my Tyler Crockett built 502 has become very hard to start. I believe it is getting too much fuel and flooding out. I am more of an automotive fuel injection guy... I see there are some adjustment areas on this carb, but I have no idea what each does. It is a marine 850 Mighty Demon carb, I believe the part # is 5563010GM? I bought boat with the engine already done by Tyler.


I have NGK TR8 plugs with MSD igntion gapped at .040

My fuel pressure regulator is reading 9 PSI with key on. The regulator seems to be making more noise than it has before.

I can see the carb squirt fuel


If anybody can please give me directions for how to adjust this carb (I cannot find the directions on the internet), that would be AWESOME!

Or maybe even some help diagnosing why it is very hard to start now all of a sudden


Thanks!!!!!!!

Im guessing it has a electric fuel pump? If 9psi is the reading on a mechanical gauge (don't trust electrics), that's too much fuel psi. It can be pushing fuel past the needle and seat and dumping in the engine. You want 6.5-7psi on a mechanical gauge. Carbs normally don't change tune out of no where.

Also, it can be clogged air bleeds. These are small little holes when looking from above the carb, in the main body. Normally you will have a total of 8 of them. 4 idle bleeds(larger ones), 4 high speed bleeds(smaller ones). Blow them out with carb cleaner using the little red straw thingy they tape to the can.

Yes it has an electric fuel pump and the regulator has a mechincal gauge. I noticed a sticker on the regulator that says it needs 14 psi inlet pressure? I'm not sure what that is supposed to mean.

For the air bleeds, it looks like they can be removed with a screwdriver? Should I remove them to clean them?

Thanks for the reply BTW

Check the float level too, when the boat is in the water. This will cause flooding also if they are not set correctly.

I got the boat running and starting good. Adjusted the fuel PSI and lowered the float bowls... What would have caused the fuel pressure to jump to 9 PSI?

Also, I was looking at my Dyno sheets from Tyler Crockett and it shows the fuel pressure to be set at 7.5 PSI.... Should I use the 7.5 PSI he used to dyno it, or lower it to the 6-7 PSI range?

Thanks again for the insite guys!!!!!!!!!!!!!!!

7 lbs and you will be good to go.