8hp Johnson water out of exhaust

[Maddoxsdaddy]

Hi all. I just picked up an 8hp Johnson short shaft for my Jon boat. Runs at idle ok but no power when in gear and on the gas and runs very rough. I noticed water coming out of the exhaust. I’m no mechanic but that just doesn’t seem right and it seems like I’ve been had. Probably why I’ve got no power. Head gasket, cracked power head, or something else possible? Yes, it does get water out the tell tale as the lady I got it from “just had water pump replaced”...
Frustrated as I was hoping to get my son on it this weekend for a little River fishing.

 

[Maddoxsdaddy]

Update... pulled the plugs, looked in the cylinders, all looks ok. So I’m ruling out cracked cylinder walls.

 

[oldboat1]

Go after the simpler stuff/tests first. Measure spark with an open air tester (auto parts store). Check compression. Post actual numbers.

 

[Maddoxsdaddy]

Go after the simpler stuff/tests first. Measure spark with an open air tester (auto parts store). Check compression. Post actual numbers.

Lower compression could possibly show a head gasket leak, correct?

 

[oldboat1]

Yes. But if you pull off a head to replace a gasket, you need to refinish the mating surface particularly if you suspect overheating. (They warp, whether overheated or not.) Simple job, but important.

 

[Vic.S]

Hi all. I just picked up an 8hp Johnson short shaft for my Jon boat. Runs at idle ok but no power when in gear and on the gas and runs very rough. I noticed water coming out of the exhaust. I’m no mechanic but that just doesn’t seem right and it seems like I’ve been had. Probably why I’ve got no power. Head gasket, cracked power head, or something else possible? Yes, it does get water out the tell tale as the lady I got it from “just had water pump replaced”...
Frustrated as I was hoping to get my son on it this weekend for a little River fishing.

The cooling water mixes with the exhaust.
Most leaves underwater with the exhaust where you wont see it.
Some will be blown out of the back pressure relief port on the back of the leg.

Check the compressions as advised.

Check that it is firing on both cylinders.
How good are the sparks. They should jump 7/16" if it is CD ignition. A bit less if points ignition

Dont start pulling things to bits until you have done these basic tests.

But what year model is it ? What is the model number?
Always quote the year and preferably the model number when asking for advice.

 

[tpenfield]

It's called a "Wet Exhaust" . . . It is supposed to have water in the exhaust. Water mixes with the exhaust in the exhaust port area of the powerhead so as to cool the exhaust. It is a thing with marine engines . . . both outboard and I/O.

So when running you should see water spitting out of the upper exhaust port just below the cowling.

 

[Maddoxsdaddy]

Thanks for the input. I’m not an outboard guy and by videos I had watched I didn’t see water coming out the exhaust. Thus my initial question.
Model number J8REEM
Serial number G 04556249
Manufacturer date 08/98
Compression top cylinder 105 and it would hold at that pressure
Compression bottom cylinder 110 and it holds as well. Used a nice snap on tester.
So, compression is ok. Power loss now sends me to fuel and spark. Checked plugs, good hot spark.
Cleaned wire screen at pump.
New 93 octane fuel mixed 50:1
Still idles fine just no power and it’s pretty jumpy.

 

[saltchuckmatt]

Thanks for the input. I’m not an outboard guy and by videos I had watched I didn’t see water coming out the exhaust. Thus my initial question.
Model number J8REEM
Serial number G 04556249
Manufacturer date 08/98
Compression top cylinder 105 and it would hold at that pressure
Compression bottom cylinder 110 and it holds as well. Used a nice snap on tester.
So, compression is ok. Power loss now sends me to fuel and spark. Checked plugs, good hot spark.
Cleaned wire screen at pump.
New 93 octane fuel mixed 50:1
Still idles fine just no power and it’s pretty jumpy.

Compression is a little low but I've seen them run fine all the way down to 90lbs. Its not holding pressure because your compression tester wont let it go down unless you release your pressure. You would have to do a leak down test in order to do that and most likely that is not your problem. I suspect and its almost always the problem is crap in your carb. Ethanol fuel and/or it sitting around will cause the carb to get junked up. Another thing to try first though is run the outboard and when it starts to bog down pump the fuel ball at the gas tank and see if it starts to run right. If it does rebuild the fuel pump.

Good luck.

PS Running 92 octane is not required

 

[Maddoxsdaddy]

I had run it previous to this video. But here’s the general idea. Runs smooth until water starts coming out exhaust. I guess this is normal? Doesn’t get much power when I twist the throttle. Pumping the bulb didn’t seem to make any difference.

 

[Maddoxsdaddy]

I had run it previous to this video. But here’s the general idea. Runs smooth until water starts coming out exhaust. I guess this is normal? Doesn’t get much power when I twist the throttle. Pumping the bulb didn’t seem to make any difference.

I understand I don’t have to run 93 however, that’s what I sell at the marina I manage since we can’t sell non-ethanol fuel within city limits. Stinks but that EPA giving incentives to cities and towns back in the 80’s to run this reformulated gas (RFG) makes it impossible for me to sell it.

 

[racerone]

What is the model # of this motor ?-----Was it a long shaft now converted to short shaft.---Yes , no or no idea ?

 

[Maddoxsdaddy]

What is the model # of this motor ?-----Was it a long shaft now converted to short shaft.---Yes , no or no idea ?

Model and serial number are in a comment above. Don’t believe it’s a convert to a short shaft.

 

[racerone]

Checked exhaust for blockage ?

 

[oldboat1]

Use of choke cleaner (?) indicates to me that that the carb may need cleaning.

+1 on an exhaust blockage. Pull off the l.u. and use a flashlight to look up in the leg. It's a favorite for mouse nests, wasp nests, etc. Might be able to troubleshoot and clean w/o disassembly.

 

[tpenfield]

What @racerone said. Exhaust blockage.

My guess is that there is some sort of blockage in/around the powerhead that begins to fill up with water. Shortly after starting the engine water reaches the area of the lower exhaust port, causing the engine to faulter. It might even be pulling a bit of water into the lower cylinder. So, check for any signs of such.

 

[Maddoxsdaddy]

Use of choke cleaner (?) indicates to me that that the carb may need cleaning.

+1 on an exhaust blockage. Pull off the l.u. and use a flashlight to look up in the leg. It's a favorite for mouse nests, wasp nests, etc. Might be able to troubleshoot and clean w/o disassembly.

Pull off the what now? Lol!
I opened up the fuel pump and cleaned the screen and crud out last week. Thus the carb cleaner. It’s on standby for if I go to the carb.

 

[Maddoxsdaddy]

Pull off the what now? Lol!
I opened up the fuel pump and cleaned the screen and crud out last week. Thus the carb cleaner. It’s on standby for if I go to the carb.

LU. Lower unit. Duh. Eyes had a hard time seeing it was a lower case L. Haha