1998 4.3L LH vortec Mercrusier top end issues

[Stillreelin]

Two years ago I put a remanufactured engine in my 21' sea pro. I put new exhaust, intake (Factory), edelbrock 600 4 barrel carb(Had the weber 4 barrel on it), electric fuel pump(gauge shows 7 psi) , plugs, wires, cap, module, icm, coil, and a fresh water system. The engine, carb and intake all came from Michigan Motorz. I have threw the kitchen at this thing. I have tried adjusting the carb with different jets and metering rods. Running .089 jets in the primary and secondary with the orange spring and .068x.057 metering rods. With the thunderbolt V ignition I have ground it and based the timing to 10 degrees BTDC. So on the trailer it runs great. In the water it will get up on plane fine but after 3400RPM the engine will start surging and you can hear little muffled popping noises. Any suggestions on What else I could try? Is that standard jetting and metering rods for this engine. If not what can anyone suggest to try? Any help would be great been trying to figure this out for a while now.

 

[Bondo]

Re: 1998 4.3L LH vortec Mercrusier top end issues

Two years ago I put a remanufactured engine in my 21' sea pro. I put new exhaust, intake (Factory), edelbrock 600 4 barrel carb(Had the weber 4 barrel on it), electric fuel pump(gauge shows 7 psi) , plugs, wires, cap, module, icm, coil, and a fresh water system. The engine, carb and intake all came from Michigan Motorz. I have threw the kitchen at this thing. I have tried adjusting the carb with different jets and metering rods. Running .089 jets in the primary and secondary with the orange spring and .068x.057 metering rods. With the thunderbolt V ignition I have ground it and based the timing to 10 degrees BTDC. So on the trailer it runs great. In the water it will get up on plane fine but after 3400RPM the engine will start surging and you can hear little muffled popping noises. Any suggestions on What else I could try? Is that standard jetting and metering rods for this engine. If not what can anyone suggest to try? Any help would be great been trying to figure this out for a while now.

Ayuh,.... My guess is, either the secondary jets are too small, the needles to big, or they're plugged up with something...

Yer description says it's goin' Lean....

 

[RogersJetboat454]

Re: 1998 4.3L LH vortec Mercrusier top end issues

What are your plugs saying when you read them?

 

[Stillreelin]

Re: 1998 4.3L LH vortec Mercrusier top end issues

Raining out today. But I just ran it the other day. I will pull and check again asap

 

[Stillreelin]

Re: 1998 4.3L LH vortec Mercrusier top end issues

Ayuh,.... My guess is, either the secondary jets are too small, the needles to big, or they're plugged up with something...

Yer description says it's goin' Lean....

Do you think I should go up to the a .101 secondary jet with the same metering rods or go to a 68x42 on the metering rods? Any ideas will help.

 

[Bondo]

Re: 1998 4.3L LH vortec Mercrusier top end issues

Do you think I should go up to the a .101 secondary jet with the same metering rods or go to a 68x42 on the metering rods? Any ideas will help.

What are your plugs saying when you read them?

Ayuh,.... Yer spark plugs will tell ya what needs doin', Better than We can....

 

[Stillreelin]

Re: 1998 4.3L LH vortec Mercrusier top end issues

Here is what I've done so far.Got out my vacuum/pressure gauge and run a clear hose so I could see if I was getting air bubbles. There was a good amount of air bubbles flowing through the line. The vacuum read between 4 and 5. I started from the fuel tank and made sure the vent hose was wasn't clogged. Then I cleaned and checked the screen and tube inside the tank. Then I replaced the check valve. Ran a new fuel line and double hose clamped it. Had no air bubbles and vacuum was a little under 2 on a 81 gallon tank. I now had a solid 7 psi at the carb, it bounced a few times to 6psi. Before it would bounce between 3 and 7 psi. So I will double check the timing today and take her out Saturday for a test run. I hope that it was the air bubbles causing the lean condition when the 4 barrel opens.

 

[achris]

Re: 1998 4.3L LH vortec Mercrusier top end issues

If you suspect a supply problem, take an outboard remote tank out with you. Hook it directly to the fuel pump and see how you go...