1992 Malibu skier bogging down at 3000 rpm

[Jdbro82]

The boat will idle great and cruise around in gear at low speeds no problem. But once you get to about 3000 rpm it will start bogging down and go up and down with speed until I pull the throttle back and start over. I have changed the two filters and the fuel pump so far and still doing it. Should I look into the MAP and IAC sensors? 

[Jdbro82]

Also the spark plug wires and spark plugs, cap and rotor as well as the coil was replaced just last year. But a buddie of mine is saying he thinks the coil was defective so I will replace that and the fuel line that goes from the gas tank to the fuel water separator next. Some advice would be great because this thing is whooping me 

[justgary]

Carb or injected?  Did it go bad slowly or all of a sudden? 

[Jdbro82]

It’s a carb, and all of a sudden started doing the problem 

[drh]

Have you checked the carb yet? Sounds like it could be a problem with the secondaries. I would verify you're still getting fuel to the secondary bowl and that the secondary plates are opening fully. Assume they are vacuum secondaries so the diaphragm may have gone bad, or if it happened suddenly maybe the linkage came off.

[Jdbro82]

Ok I will check it tonight after work 

[justgary]

Or a float quit floating, or a jet got crud in it, or....  If you don't know when the carb was last rebuilt, or if you do know and it was a long time ago, it is time to do it.

You could try a quick fix:  Run the engine at a slightly high idle and use your hands to suddenly and completely cover the horn until the engine dies.  The engine will tend to try to suck your hands in, so it will scare you the first time you try it.  If you can get the choke to close completely, you could do that instead and then immediately cover the horn with your hands to shut off the rest of the air flow.  The idea is to do it fast enough that you severely choke the engine so that the vacuum pulls any crud through the jets in order to clear them.  Getting the carb horn covered quickly is the key, since you need plenty of vacuum to pull junk through the jets.  After you do this, the engine will be flooded, so you may need to crank it at wide open throttle to clear the excess fuel.

If your problem was crud in the jets, this should pull it through and restore performance until the next glob of crud gets in the way.  A carb bath is really the only way to get it squeaky clean inside, but this will do in a pinch.

[Jdbro82]

Ok yes don’t think it was ever rebuilt so I agree probably time. But I will try that tonight and see if it can clear it up a little I appreciate everyone’s suggestions. Just got the whole interior done and now giving me this problem so it’s more than aggravating 

[Woodski]

There is an anti siphon valve on the fuel tank vent line, if this sticks closed it can create a vacuum in the tank.

[Jdbro82]

I really appreciate everyone’s advice on here if your ever in central Florida give me a call. Pulled people all day on it had a blast. But I ran some more carb cleaner through it yesterday and checked the carb real good looks fine and is running better now. Had to change all my spark plugs because i sprayed a bunch of carb cleaner in there when the motor was off like a dumbass, and now it’s running like a champ. But taking like three cranks to fire up and have to have it in neutral wide open in reverse and once it fires up runs great. What could be causing this issue? I was thinking spark plug wires but don’t know. 

[justgary]

1 hour ago, Jdbro82 said:

I really appreciate everyone’s advice on here if your ever in central Florida give me a call. Pulled people all day on it had a blast. But I ran some more carb cleaner through it yesterday and checked the carb real good looks fine and is running better now. Had to change all my spark plugs because i sprayed a bunch of carb cleaner in there when the motor was off like a dumbass, and now it’s running like a champ. But taking like three cranks to fire up and have to have it in neutral wide open in reverse and once it fires up runs great. What could be causing this issue? I was thinking spark plug wires but don’t know. 

A can of carb spray and a real dip in carb cleaner are different.  The one gallon can of cleaner (with a parts basket inside) is a good choice.  While you are at it, get a carb kit so you have new rubber parts in it.  Use compressed air to blow each tube and orifice as well as the jets.  If you don't have compressed air, that's when you can use the spray can of cleaner.  You might be surprised at the difference once you get it all back together.

It is also probably time for a complete tune up, which includes plug wires in addition to the regular stuff.