99 moomba outback Noise under load

[Bondo]

Re: 99 moomba outback Noise under load

More bad news. I have milky brown oil now on the dipstick. Did not have it on Sunday or Monday when I first heard the knocking sound. Checked the oil a little while ago and saw the water in it.

I think I'm in for an engine overhaul. The sound is the same as when it first happened. I think the bearing was going all year and then finally gave out. I probably damaged it more by having several people hear the sound it made, and then running it with higher octane fuel.
Possibly damaged the jacket from the rod and piston clattering about.

Ayuh,... How over-full is it on the stick,..??

Before ya put another motor in that boat,...
Thoroughly check out the Fuel System...
From the tank vent, All the way through...
I'd bet ya ran lean, 'n detonated it to death... It's really hard to hear in a boat...

The Best, Quickest, 'n in the long run, Cheapest way out is a reman Long Block on a pallet....
Throw yer hardware on it, 'n go Boatin'....

Btw,... I'd rebuild the Carb, just to look it over...

 

[mr408]

Re: 99 moomba outback Noise under load

We found an air leak when we looked at it this a.m. causing it to lean out. The carb has a angle block to help the carb get level. There was no gasket between the carb and the block, only the angle block and the intake. Will check fuel system, tank vent, etc. Changing oil, filter and fuel separator and putting new gaskets on at 5 pm.

Found out that it was gas in the oil. Dip stick wasn't over full by much. Strong gasoline smell from the oil filter. Fuel filter had crud, but zero water. Changed oil and will put the gaskets in and water test it tonight.

 

[mr408]

Re: 99 moomba outback Noise under load

Knock is still there after oil change, filter and two gaskets. Sounds just like it did on the Sunday the 31st. Running a bit rough. Could it be valve clatter? Maybe loose valves?

We're going to try a hotter plug.

 

[mr408]

Re: 99 moomba outback Noise under load

Boat ran very smoothly after the rebuilt carb was put on with two gaskets. Idle - 850 no skips. Could hear a slight knock when hitting the throttle hard in neutral. Put it in the water and idled it for a minute and then it started to run rough. Shaking the boat rough. Knock was back just like before. Idle shot up to 1700 rpm from 850 and stayed there until I fiddled with the idle screw. Calmed down to 1000 but still running rough. Put a quart of engine oil additive/cleaner in (took out a quart of oil first) ran it for 1/2 hour in idle speed around the lake. No change. Had a timing light on it and it was advanced a few degrees. Set it to where it should be.

 

[mr408]

Re: 99 moomba outback Noise under load

Put a hotter plug in and retarded the timing. Knocking is gone. Will run the 25 gallons of fuel left through it and then put fresh gas in and advance the timing back, as well as putting the old cooler plugs back in. Put the plugs under a magnifying glass and saw no pitting around the electrode due to excessive detonation.

 

[mr408]

Re: 99 moomba outback Noise under load

Boat has 20 gallons of 93 octane in it. Advanced the timing a bit - no problem - power was better. Advanced a bit more and the knock came back, although it was to a lesser degree.

Electronic distributor, not loose, no play, no 'hanging springs' on this model. Oil pressure is fine, it isn't valve clatter. Still idles poorly. After a ski run the idle will run up to around 1500 rpm and then slowly back down to around 1000. Boat will barely idle out of the cove at 750, and then stick at around 1000 after a ski run.

Boat is at operating temp of 160 -170 not overheating or cold when this happens.

Changed cap and rotor but not plug wires yet. May have to re check the carb rebuild. Any suggestions?

 

[mr408]

Re: 99 moomba outback Noise under load

New plug wires are in. Boat runs a bit better. Will check the timing chain and see if it has stretched.

 

[mr408]

Re: 99 moomba outback Noise under load

New plugs in and it is idling better and holding speed. Advanced the timing a bit and the knock came back. Checked for air leaks all around manifold, carb hoses etc. Nothing. Any ideas?

 

[keehr]

Re: 99 moomba outback Noise under load

Hate to say it, but it sounds like a bad head gasket. Have a leak down test completed with cylinders 3, 5, 4, and 6. I've had 2 of these 5.7 Vortecs blow head gaskets between the middle cylinders. Heat is the cause. The longer you run it the worse off you'll be. I made the mistake the first time, and when I finally figured it out, not only was the gasket gone, but the heat and pressure had also torched the mating surface on the block side..full engine replacement. On the 2nd boat, I was able to get away with having heads machined and new gasket put on.

Good luck!

 

[mr408]

Re: 99 moomba outback Noise under load

Will do a leak down this week and get back to you. Thanks

 

[mr408]

Re: 99 moomba outback Noise under load

Gasket was shot between cylinders on both sides. Heads were damaged as well. New block and heads and I was back on the water in two weeks. Thanks for the help, and next time I'll know as soon as it happens.

 

[Bondo]

Re: 99 moomba outback Noise under load

Gasket was shot between cylinders on both sides. Heads were damaged as well. New block and heads and I was back on the water in two weeks. Thanks for the help, and next time I'll know as soon as it happens.

Ayuh,... Thanks for the update,... Glad to here yer back on the water,...