1993 5.0L Mercruiser v8 305 choking after 3500 rpms

[dlogvine]

This is newly rebuild engine that I installed on 2006 Baja Islander 202. This engine was completely rebuilt late in 2017 and was waiting to be dropped in the right boat. New gaskets, bored .30 over, rebuild heads, new oil pump, pistons, new camshaft, polished crankshaft. Basically new engine. 4 barrel Rochester Carburetor was also rebuild. Last year I bought a beaten up but still solid 2006 Baja Islander 202 hull and re-upholstered it, dropped this engine in (wiring was the same with exception of the gear lube monitor and older, mechanical fuel pump. It starts from the turn of the key. Runs fine on idle and lower rpms up to 3500 and pulls strong, towed a large 4000lbs+ boat without a problem. Prop was originally aluminum 14.5X19, was replaced with 14X17 SS propeller a couple weeks ago. The main problem is when the gas lever is pushed the engine goes up in RPMS to about 3700-4000 rpms and then chokes for a sec, drops to 3200-3400 rpms and then catches up and repeats the same. Does not go higher than 4000rpms. My guess is that carb is getting overflown with gas and needs adjustment, but just wanted to ask if there could be anything else causing that. Timing is set correctly, it idles at 700rpm perfectly, purring very quietly like a big cat.
Thank you

 

[Scott Danforth]

check your float level and fuel pressure

 

[Bondo]

My guess is that carb is getting overflown with gas and needs adjustment, but just wanted to ask if there could be anything else causing that.

Ayuh,..... If it's over-fuelin', the plugs will be black,.... If lean, they'll be white,.....

 

[dlogvine]

I am replacing the fuel pump. It was more than a year ago since i rebuild this engine and i completely forgot that i wanted to switch the pump at a later time. The one currently sitting is from 1993 original. If the problem persists, will start going along the fuel line.

 

[tank1949]

Check fuel/line/filters. It sounds like starving for gas. I had a Proline MC dual V8s that had screen inside fuel pick up that became clogged with crappy gas. I suspect it had sat for some time. I removed tubes and cleared and recycled all gas back through filter until MOST crap removed. One was complete blocked. The former owner had also installed automotive electric fuel pumps that was no match to Sierra marine pumps that I later installed.

 

[dlogvine]

Im putting a new fuel pump, old one looks like is original from 1993. Will go from there.