1987, 454 Help!

[jmgutzz]

The boat is running rich, changed carburetor, plug wires, plugs, Dist cap, point. checked fuel pressure, changed fuel filters, water separator filter, good fuel, timing is dead on 8 degree. has good cylinder pressure. been at two mechanics and both says , I don't know, lets pull the motor. Another one tells me to cut my loss and move on. Good boat. Help!

 

[Lou C]

what? pull the engine because it's running rich? What kind of mechanic says that?!
Quadrajet carb? Is it set up correctly? These are complex carbs you have to know what you are doing to get them to work right. If the engine is running rich you need a real mechanic who knows Quadrajets if that's what you have. A good one set up right is an excellent carb. Rich running can be leaking needle valve, incorrectly intalled needle valve hanger (the hanger for the valve does NOT go in one of the holes on the float arm, it just hooks on the side) float level too low, leaky main bowl plugs, etc.
You can see the wire hanger for the needle valve in the bottom of the pic below.

 

[km1125]

I agree with LouC's post. Carbs are great when they're working and setup great. If it's running rich it's likely just something simple in the carb, like a float valve not seating properly. Do ALL the plugs show rich? Is it only rich at idle or rich under load/at speed too? Are you sure the choke butterfly is opening (and staying open) when it's warmed up? THe earlier units used a "divorced choke" and the bi-metal spring would come loose from the pivot, so the choke would close after the engine was warm, causing a rich condition. Easy fix for that one.

 

[jmgutzz]

what? pull the engine because it's running rich? What kind of mechanic says that?!
Quadrajet carb? Is it set up correctly? These are complex carbs you have to know what you are doing to get them to work right. If the engine is running rich you need a real mechanic who knows Quadrajets if that's what you have. A good one set up right is an excellent carb. Rich running can be leaking needle valve, incorrectly intalled needle valve hanger (the hanger for the valve does NOT go in one of the holes on the float arm, it just hooks on the side) float level too low, leaky main bowl plugs, etc.
You can see the wire hanger for the needle valve in the bottom of the pic below. View attachment 351548

New carb was put on and I even sent it back to the manufacture to have it checked out. the Mechanic said he ordered another one with out electric chock and the motor still did the same thing. When I bought the replacement carb, I went from intake choke to electric choke. The boat ran one day great , then the next day the plugs a fouled and can't get up on a plane.

 

[Lou C]

keep in mind that the electric choke needs a constant 12V supply or it will close, they are better called "electric opening chokes". Normally with no power to the terminals they will close and the engine will run very rich.
I have the old style divorced choke with the spring mounted on the intake manifold above the exhaust cross over and as long as the engine warms up properly it works fine.

 

[jmgutzz]

keep in mind that the electric choke needs a constant 12V supply or it will close, they are better called "electric opening chokes". Normally with no power to the terminals they will close and the engine will run very rich.
I have the old style divorced choke with the spring mounted on the intake manifold above the exhaust cross over and as long as the engine warms up properly it works fine.

I think I will pull the carb off send it back and exchange it for the old style carb which was on the boat before. I pick the boat up on Saturday and I will order one next week. I will let you know what happens..

 

[alldodge]

You sure its to much gas or burning oil?
Got pics of the plugs?

 

[Bondo]

I think I will pull the carb off send it back and exchange it for the old style carb which was on the boat before. I pick the boat up on Saturday and I will order one next week. I will let you know what happens..

Ayuh,..... Welcome Aboard,...... What carb is on it now,..??
What carb was on it before,..??
Does this motor have a block mounted mechanical fuel pump,..??

 

[Scott Danforth]

measure your fuel pressure for a carb, 3-7 psi

 

[Bt Doctur]

+2 check the pumps pressure

 

[Scott06]

New carb was put on and I even sent it back to the manufacture to have it checked out. the Mechanic said he ordered another one with out electric chock and the motor still did the same thing. When I bought the replacement carb, I went from intake choke to electric choke. The boat ran one day great , then the next day the plugs a fouled and can't get up on a plane.

And choke is fully opening every time? Verify its opening or turn the choke stove such that it cant close, clean or replace spark plugs.

had similar issue on my 3.0, went through needle and seat replaced float etc, at parts counter mechanic says what you working on…. Check choke is opening. sure enough i tear into carb without checking choke function. Of course choke wasnt opening …

 

[QBhoy]

Couple of things to add maybe.
I’d wonder around the choke sticking on for sure. Once it has and ran rich…it sure doesn’t take much to foul the plugs badly enough to have the effect of running poorly even after the choke has been sorted or ruled out. Can only rule this out with new plugs after each time it’s ran rich, I’d say.
Other thing I’ve seen twice this year for sure, is a rich running condition caused by the mixture setting being messed with to try and counter act the fact that the engine was getting occasionally starved of fuel, caused by the check valve after the fuel tank…restricting fuel intermittently. Can also cause a lean condition up the rpms and rich at low rpms. Can confuse the brain a little at first. But certainly this was to blame on both occasions. One was a 7.4 and the other was a 5.7.

 

[jmgutzz]

measure your fuel pressure for a carb, 3-7 psi

how

 

[alldodge]

They make better ones but the HF one will get it done
https://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html

Need to make a Tee and use fittings to connect between carb and pump.

Can also get the motor running for a few seconds so the pump fills the carb fuel bowl. Shut motor OFF and remove fuel line going to carb. With a rubber piece of fuel line connect gauge direct to fuel line and restart motor.

It will run for several minutes before fuel runs out. Check idle and rev it up to 1500 to 1800 and note readings

 

[Scott Danforth]

this fitting helps

Fuel Fitting Connector 91-18078 - CP Performance

Fuel Fitting Connector 91-18078

www.cpperformance.com