Motor vibrating, smoking through pee hole, weak steaming stream

I have a 88 johnson 15hp long shaft outboard on my 14foot jon boat. It is a stubborn 2 stroke but works fine if you know how to deal with it. It is a long stroke that I had on too short of a transom, so Just before summer I replaced the transom on the boat and added a 5 in lift to get this motor to the correct height settings for the cavitation plate. Before I was having problems with the motor working too hard and inefficiently. On a couple longer rides last year it had started to smoke a little

Now that I have it back in the water at the proper height Ive noticed other problems. I took the boat to the water and was just checking the new transom for leaks and taking a couple laps to see how the motor was working with the lift. The motor was considerably faster and everything seemed be going swimmingly. I noticed a weak stream and was very happy with the strength and water tight transom so I took it out of the water pretty quick.

When I was backing into my drive way that day I thought with the lift I had added I did not need to raise the motor entirely but I was wrong. I scraped the fin and put a small bend in it.

So I replaced the impeller. The old one didn't look that bad but I replaced it anyway. I tried it on the water and there was a stream but still very weak. There was also a vibration in the motor that I attributed to the bend in the fin. After a while of having the boat out the stream stopped completely. I took it home and took it all apart again. I double checked everything was in the correct orientation again before putting it back together. I also took the bend out of the fin and sanded everything down smooth. I check the prop and it was fine.

I started it again on the muffs but still there was a trickle to no stream.

I ran some wire up in the peephole and sure enough sand came out. I punched some air through the peehole and a clog was released. I was ecstatic. I tried the motor again on the muffs and water came out in full stream. It started to give me 5 seconds of good flow then 1 second stop on a cycle. I think this was the thermostat letting the engine come to temp. Looked like everything was good to go.

I tried this morning to go fishing. The motor started quickly with good stream so I pushed off. The engine was vibrating pretty hard still but working and then 1 minute later the engine started pushing out white smoke from the pee hole with a weak/inconsistent stream. The smoke started coming out thick when I shut it down.

I let it sit for a few minutes at the dock and started it again. It cranked right over and looked fine for a few seconds then steam started coming off the peehole exhaust water. It escalated quickly and I shut it down again.

I was treating these symptoms as separate but now I'm thinking they are all connected. I have been learning everything as I go and have gotten by for a while but this is getting a little over my head. Any advice would be great!

Thanks

The cavitation plate on a 15hp engine on a Jon Boat should normally be about 3/4" below the keel at the transom... no more than 1".

The top portion of the copper water tube seats in a rubber grommet that unfortunately is prone to deteriorating and folding over, effectively creating a shut off valve. It's necessary to remove the powerhead and lower unit to replace it.

Hopefully you had the water tube inserted properly into the impeller housing... if not, the water pipe may have gotten shoved/bent somewhat upwards. Check that the tube inserts as far as it should.

I'd recommend you double check your work, making sure that the impeller plate isn't scored or that the impeller housing isn't pitted on the inside. If you reinstalled the pump without sealing it, it would be a good idea to seal the impeller plate to the gearcase and the impeller housing to the plate. Sealer adhesive listed below.

OMC Adhesive is now Bombardier 3M Product #847 and may be listed as Scotchgrip 847, part number 776964.

The cavitation plate on a 15hp engine on a Jon Boat should normally be about 3/4" below the keel at the transom... no more than 1".

The top portion of the copper water tube seats in a rubber grommet that unfortunately is prone to deteriorating and folding over, effectively creating a shut off valve. It's necessary to remove the powerhead and lower unit to replace it.

Hopefully you had the water tube inserted properly into the impeller housing... if not, the water pipe may have gotten shoved/bent somewhat upwards. Check that the tube inserts as far as it should.

I'd recommend you double check your work, making sure that the impeller plate isn't scored or that the impeller housing isn't pitted on the inside. If you reinstalled the pump without sealing it, it would be a good idea to seal the impeller plate to the gearcase and the impeller housing to the plate. Sealer adhesive listed below.



My cavitation plate is lined up just under the keel. This part should be correct. I think that the water tube is all in line too. I had cleaned and resealed the bottom of impeller plate as well as sealing the impeller housing to the plate.the water. I cleaned the rubber insert at the top of the water pump and checked the rubber from the top of the impeller housing to the the rubber insert into the motor. Everything seemed to line up cleanly.

The impeller plate looked fine with a minimal wear from the impeller spinning and the impeller housing was tight too..

I am sure I will have to take it all back apart but I have been getting frustrated and running out of ideas with this thing. Thanks for the advice

It sounds like the motor overheated at one time. Finding sand in the pee-hole would indicate that I would look at he grommet under the powerhead like Joe said.. As far as the vibrating look at the prop you may have bent a blade as that would have hit before the skeg. Steam coming out of the pee-hole indicates a lack of water.

In addition to my previous reply..... your mention of white smoke could indicate a slightly leaking head gasket which may allow a fine stream of water to enter the combustion area. This could have been caused by overheating as "flyingscott" suggests. If this condition exists, it could very well cause a stalemate.... water coming up, combustion flowing past the gasket into the water passage area and preventing the water flow from traveling normally.

Do a compression test before going forward,this will tell you if head gasket is bad,caused by overheat condition!!Pull plugs, if steam cleaned you have more than likely gasket issue on head or exhaust side of engine

Right, I feel like the water pump and housing is sealed and in order. The grommets are worn but not cracked and dry and the water flow just fluctuates so wildly from the pee hole. But I am not sure about the grommet under the power head sounds like a huge pain to check. The smoke was super white and coming out of the pee hole not the exhaust. Could a bad head gasket also explain the vibration in the motor?

Thanks, this motor has been kicking my ass. Think you finally get everything in order and then boom catastrophic failure

I just pulled my plugs and the top one was super clean barely a lick of oil on it and the bottom one was as just as dirty as it should be. Could this still be gasket issue?

Is there a way to do the compression test with out the motor cooling it self? There is zero water coming through the pump

a compression test is done with engine cranking not running Remove all plugs,engine needs to crank 200-300 RPMS,fully charged battery, screw in tester,crank for 4-5 revolutions,take reading, one cylinder at a time Do entire test twice,record readings. All cylinders must be within 10% of each other. Super clean plugs are a sign of water intrusion in cylinders, Compression tester can be done hot ,warm, or cold, Tester can be borrowed or rented from auto parts outlet.

john-paul said:

I just pulled my plugs and (1) the top one was super clean barely a lick of oil on it and the bottom one was as just as dirty as it should be. (2) Could this still be gasket issue?

(3) Is there a way to do the compression test with out the motor cooling it self? There is zero water coming through the pump

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1 - Clean, like brand new, white porcelain at electrode? ... Indicates possible fine water spray.
2 - In a word.... Yes.
3 - Engine is NOT running, all spark plugs are removed, key is in OFF position. Engine is cranked over via a small jumper wire leading from the (+) battery cable terminal of the starter solenoid to the small 3/8" nut terminal on the solenoid that engages the solenoid (NOT the 3/8" ground nut terminal).

Thanks all for the advice. I was really frustrated with this motor and took a little vacation from it. I went back at it today with a clean start. I compression tested and both cylinders ran at 80PSI. I will check the impeller out tommorrow and check all my work. It still has me a nervous because if the water pump fixes easily then I still have substantial vibrations. Thanks

joereeves said:

1 - Clean, like brand new, white porcelain at electrode? ... Indicates possible fine water spray.
2 - In a word.... Yes.
3 - Engine is NOT running, all spark plugs are removed, key is in OFF position. Engine is cranked over via a small jumper wire leading from the (+) battery cable terminal of the starter solenoid to the small 3/8" nut terminal on the solenoid that engages the solenoid (NOT the 3/8" ground nut terminal).

Click to expand...

I wanted to give an update.

The vibrations ended up coming from a bent drive shaft. I ended up getting a used short shaft and converting my long shaft motor. After fixing that the motor starts and runs fine but still has the same inconsistent weak stream which causes steam and smoke to eventually come out of the pee hole. I blew air through the water line with out the lower unit on and could only get the same weak inconsitent airflow. The next step will be one of Joe Reeves first responses and look under the power head at the grommet.

There is no earlier way to fix this, correct? Cant stick a pipe in the water hole and just reverse the bend I don't guess? I have seen a lot of time and money on this thing recently and I am not looking forward so much to this...

john-paul said:

The next step will be one of Joe Reeves first responses and look under the power head at the grommet. There is no earlier way to fix this, correct?

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Unfortunately, no.... there are no shortcuts. You'll see why when you finally get to that grommet. Keep us in the loop.

joereeves said:

The top portion of the copper water tube seats in a rubber grommet that unfortunately is prone to deteriorating and folding over, effectively creating a shut off valve. It's necessary to remove the powerhead and lower unit to replace it.

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John Paul,
Please take Joe's advice and remove the power head to check the water tube grommet. You'll need to order a new grommet and base gasket for the power head. Both are available on the marineegine.com parts store.

The reason I insist is that I too chased a low flow condition on my '79 Evinrude 9.9 much like you are now. Water pump, thermostat, T-stat housing.....I looked at all the options and the engine just didn't have good water flow. Finally I popped on here and Joe suggested looking at the water tube grommet. I hated the idea of pulling the power head but dug in because i was out of options.

It took about 2 hours to get down to the base and sure enough, the grommet was deformed and had a flap that nearly covered the entire water tube. While I had it all down I also checked the water passages in the exhaust plate which were pretty much clear. After replacing the grommet and making sure all passages were clear the motor now has good water flow and doesn't overheat anymore.

You really need to check that grommet because your issue sounds identical to what happened to my motor.

KJ

So I pulled the head and lower unit and both of the grommets where completely disintegrated, one was distended. I replaced them both but I slighltly damaged the bottom 1/8in of the exhaust grommet. I was impatient and made a bad gamble putting it together with out wanting to wait on another part. she came back together pretty easy and she started right back up with a full pee stream, the timing had also been way out of whack and I was able to line it back up. I was ecstatic.

When I got it on the water today for the trial run she started right up and sounded great. When I put it in gear it engaged but there was exhaust coming out of the engine compartment under the powerhead. this exhaust is choking the engine when the lid is on and revving up when it comes off and comes in contact with the air. This was not identifiable with the muffs on because the midsection was not pressurized.

I am a glutton for punishment and am going to go back and replace the exhaust grommet again.

I am still concerned about a jerky vibration the motor has to the sides. I there is not much more to say to describe it but I am concerned with the motor being a dud even after fixing so many other problems. Would it be beneficial to pull power head to check for filing? Is there anything else I should look for while I have it all apart

The little aluminum boat and motor I bought were a lemon and not at all as described. As I have gotten deeper into the motor I have found bigger problems and wondering where the cut off point is.

Thanks for the guidance

john-paul said:

When I put it in gear it engaged but there was exhaust coming out of the engine compartment under the powerhead. this exhaust is choking the engine when the lid is on and revving up when it comes off and comes in contact with the air. This was not identifiable with the muffs on because the midsection was not pressurized.

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One cannot run a outboard engine in any kind of test tank with the hood on as the exhaust fumes will be drawn up into the air intake sections. The same hold true pertaining to running on a flushette on a very calm day.

If this problem occurs with the engine mounted on a boat and while underway, then I suspect that you have accidentally damaged the base gasket of the powerhead when assembling the engine.

Thanks, I have an extra one of those gaskets, and I will replace it for sure. It was hard to see exactly where it was coming from but definitely from that vicinity.

Can you tell me if the copper exhaust pipe coming from the powerhead is supposed to point directly into the exhaust port. The pipe seemed about 2 inches too long to be feasible but I wanted to make sure. I will double check if it is physically possible when I put it back together anyway. I had read that these just point downward away from the engine and just depend on the pressure in the midsection to blow it through the port.

Any ideas about the jerking?

I have the same sort of issue on my 1979 35hp 2 stroke long shaft outboard, I just replaced the water pump and it worked great for about 20 miles of boating on half power. At first the pee hold was off and on shooting water out, now Pee hole pushing out steam and a drop of water here and there and exhaust starting to get thick with white smoke when running a bit high while trying to get water pump pee hole unclogged but I think I may have your issue. With desintigrating rubber. I am going to check thermostat first for stuck closed. Not looking forward to this fix.