‘89 Johnson gt150 v6 fuel in exhaust?

[Zep25]

Looking for some help tracking down a fairly significant fuel leak coming out the main exhaust port while running AND not. 8’x8’ solid sheen on water after 5 mins stopped. Not gear oil, def fuel/oil mix. Rebuilt carbs recently that didn’t seem to help much. Compression is low, but all within 10%. Fires right up cold. See no visible fuel line leaks/issues under cowl. A little slow out of the hole, but happy with about 45mph top speed on plane. Sometimes does stall at idle and in gear on the water, but runs like a top on the muffs? Can’t in good conscience put this boat in the water with a leak. Any ideas would be appreciated.
Vro pulled by previous owner. Would a bad pump diaphragm cause the excess fuel out? Bad reeds?
Thanks!
j150stlcem 150 Cross Flow pushing a 18’ bumblebee

 

[racerone]

It only sounds good on a hose.---They all " bark and roar " and sound good even in gear on a hose.----There is no work done to turn a prop in air.------What are the actual compression numbers.----Or pull bypass covers to look at pistons and rings.----Yes a hole / tear in a standard type pump will leak fuel straight through the engine.---Not likely to be a reed valve problem unless it has composite reeds..

 

[Zep25]

Compression is 60, 62,60,61,56,63. I know.. not great. Can just low compression cause all that fuel in the exhaust? Seems to still run pretty well. ??
What should the pistons and rings look like?
Still has the original oil and gas combo pump installed. Is there an easy way to check the diaphragm? Will a visual inspection show any issues?

 

[racerone]

You either have a poor quality gauge or serious motor problems.---Test with another gauge first.----Does gas primer bulb on the hose go hard when you squeeze it , yes or no ?

 

[Zep25]

Would you even get any power out of such low compression? I assume it would be a bear to even start. ?
Gauge is a cheapy harbor freight tester tho.
Yes. Bulb seems to firm up fine.

 

[racerone]

Your motor, so up to you to do some testing / inspection as per posted info.----Guessing just does not work on these motors.

 

[Zep25]

Will def try a different gauge. Really hope that’s it.
Will also pull the fuel pump and check th diaphragm as well.
Anything else you recommend?

 

[Zep25]

Tried new gauge, slightly better but still all numbers around 65. Is this a lost cause?
Can bad compression alone cause all that fuel
in the exhaust?

 

[racerone]

Remove the bypass covers and inspect pistons and rings !!!-------Likely you will see the damage.

 

[jimmbo]

It runs on the muffs, no load or backpressure on the exhaust. I doubt it would do more than cough if the boat was sitting in the water with those compression numbers. You could pull the heads and look at the gaskets, there is a very slim chance the head bolts weren't torqued properly. Previous owners tend to forget to mention things like low compression numbers, water in the gear oil, etc, when they are selling

 

[Zep25]

That’s the thing... On the water, it idles a little rough but it gets up on plane and runs about 45mph. That’s why I didn’t understand the low compression numbers. I’m just concerned with all that fuel getting pushed out of the exhaust.
Probably just need to pull covers and take a look at the pistons and rings.
Would loose head bolts cause the poor compression problem?

 

[racerone]

After a severe overheat the head bolts will be loose.----Myself I would pull the cylinder heads off to inspect things.

 

[Zep25]

Pulled heads this morning....
I’m no mechanic so I’m not exactly sure what a scored piston feels like. But, I would guess two of my pistons are scored (#5 and #6), two others show signs of scoring but are still smooth to the touch (can’t catch my thumb nail). #1 and 2 are smooth and look good. Quite a bit of carbon build up on the piston heads 5 and 6 as well.
I also noticed all the pistons had a little bit of play/looseness to them. I’m assuming that’s due to age and wear, but is that where I’m losing all my compression?? What’s normal play for a piston head?

Or since I have two scored cylinders, am I looking at a rebuild anyway?

 

[racerone]

There is only one way to fix this.-----Time + a bundle of money.----Rebuild it.

 

[adamh1281]

I've got a 1991 200hp that has 65psi across all cylinders. It gets up on plane...slowly. on a 20ft hydra-sports cuddy. It will not start if I choke it. Once it gets started, it runs ok, but guzzles gas. 1mpg. I hate to piggy back on this post, but Its flooding out and spitting alot of fuel out of the bottom starbord cylinder when I turn it over with the plugs out. (how I get it un-flooded). We may have the same problem. It seems like all the extra gas must be pooling into the bottom chamber? Are all cylinders sealed from each other within the block?

 

[Zep25]

Damn.
is rebuilding this ‘89 engine even worth it?
Probably $2500 to do??

 

[racerone]

Adam-----A V-6 outboard like yours operates as six separate motors with a common block and crankshaft.-----So yes each crankcase is sealed and separate from the other 5 cylinders.

 

[clemsonfor]

I've got a 1991 200hp that has 65psi across all cylinders. It gets up on plane...slowly. on a 20ft hydra-sports cuddy. It will not start if I choke it. Once it gets started, it runs ok, but guzzles gas. 1mpg. I hate to piggy back on this post, but Its flooding out and spitting alot of fuel out of the bottom starbord cylinder when I turn it over with the plugs out. (how I get it un-flooded). We may have the same problem. It seems like all the extra gas must be pooling into the bottom chamber? Are all cylinders sealed from each other within the block?

sounds like a bad carburetor, misadjusted floats or bad needle valves will over fuel

 

[adamh1281]

Thank you both for the feedback! I will check the flooding cylinder's carburetor. I stuck a rag into the throat of the flooding cylinder to prevent any air, and thus gas from getting into the system, but it still spit alot of gas from that open spark plug hole. I then plugged all the carbs with rags and it still spit like a sailor. Is there any other way for gas to be flooding that cylinder? (there's some other small lines attached to that cylinder) that's why I was concerned that it was an open system in there (like my old waverunner) and it may be some other carburetor in the like or some other thing I'm not used to. I'm coming from a 1985 evinrude 50 that I could easily understand.

 

[racerone]

Adam-----When you block of a carburetor with a rag you will suck even more fuel out of the carburetor bowl.-----Please review carburetors 101