Johnson 1954 10HP QD-15: Thanks and some questions.

[dshanks]

First, I want to give a big thank you to all of the people here who have posted advice and answers to questions. I'm not a mechanic by any stretch of the imagination but I've been working on getting my Grandfather's 1954 Johnson 10HP running again. When I pulled it out of the shed it had been sitting in for 10-15 years it wouldn't start. After working on it, I took it out on the lake for the first time today! Today's trip was to adjust the carb needles as described in this forum. After the adjustments she ran great. This would not have been possible without the information I found on this forum. So thank you to iboats.com for hosting this forum and thank you to all the people who provide answers to questions.

Work done so far:
1) Cleaned and re-gapped points. No spark until this was done.
2) Replaced plugs
3) Checked lower unit lube. It's brown but not milky. Noticed that there are no washers on the lube ports. Guess I need to find a source for them.
4) Rebuilt carburetor.
5) Cleaned inside pressure tank and rebuilt pressure thank pump
6) Rebuilt the fuel connector (actually I found a guy on eBay who does it for a fee. Well worth the price. I'd probably have made a mess trying to pick the old dried rings out with a dental pick)
7) Adjusted carburetor needles as described elsewhere on this forum.

I do have a couple of questions remaining that I haven't been able to find the answers to yet:

1) The water pump seems to be good. At fast idle (start) there's a good spray of warm water out the water discharge port. At wide open throttle the spray is stronger. When the boat's not running, the bottom of the water discharge port is just above the water. I noticed that if I tilt the motor up a little, moving the discharge port a few inches above the water, the RPMs come up. Is this normal? Is it a cause for concern that the discharge port is so close to the water?

2) After running at wide open throttle for a few (5-10?) minutes, the heads sizzle when water is splashed on them. Is this normal? Can anyone tell me an appropriate temperature for the heads on this model? I know my model does not have a thermostat so I was surprised that the heads got so hot. Lake temperature was 78 degrees, so there should have been plenty of cooling available. The heads cooled down within a minute or two after returning the throttle to idle. I know for a fact that this motor has never been run in salt water, so salt build up should not be a problem.

3) Twice, I heard a loud bang a few seconds after opening the throttle wide. It sounded like the lower unit had hit something, but I was in 60 feet of water. The first bang was before I adjusted the high speed needle. The second was after adjusting the high speed needle but before adjusting the low speed needle. Is this normal? Should I be worried? Maybe it was a backfire? I did not hear any more bangs after adjusting both needles.

4) I've read elsewhere that the needles need to be "perfect." There is a small imperfection at the tip of my motor's low speed needle (see picture). Looks like someone seated it a bit too hard. Is this a cause for concern? It idles pretty well (better than my nearly new Nissan 5HP 4-stroke!) but does occasionally miss. Could the imperfect needle be the cause?




Work yet to do:
1) Find washers for the lower unit lube covers and replace lower unit lube
2) Replace the cowl bumper studs and bumpers. The studs for the old ones broke off. I tried running without the bumpers but the cowl makes an awful racket rattling at anything above start throttle.
3) Replace water pump impeller.
4) Figure out what else needs to be done based on answers to the questions above.

I'm pretty happy with this motor and want to make sure I'm caring for it properly. Thanks in advance for help anyone can give me in finding answers to the questions above.

 

[nwcove]

1.) assume that the impeller is bad, replace asap
2.) water should not sizzle on the head. ( 1.) could fix that....but keep a close eye on it
3.) did the motor jump like you hit something? if so, could be the clutch dog slipping, but from what you said, it also could just have been a lean " sneeze".
4.) that needle is a bit rough to say the least, keep an eye out for a replacement, but in essence its nothing more than a valve. (jmo)

 

[F_R]

It should not be getting that hot. Make that water pump service a priority. Depth in the water does make a small difference in idle speed due to difference in exhaust back pressure. Not something to be concerned about.
That bang like you hit something is classic. It suggests a worn clutch dog in the lower unit. It is coming out of gear, rotating 1/2 revolution and slamming back into gear. Every time it does that, it greatly increases the wear. For that reason, it should be repaired before the wear (and cost) goes up.
Yeah, "they" say the needle has to be perfect, but I say it will work like yours is. Think of it as a glorified faucet. The more you open it, the more fluid flows through. A worn one does the same thing, but it becomes a little more (or less) sensitive. A severely grooved one becomes hard to adjust.

 

[dshanks]

Thanks nwcove and F_R!

I won't run it again until the water pump is rebuilt. Do you know if the water pump kit from a QD-16 (the closest model I've been able to find a parts catalog for) will fit the QD-15? According to leeroysramblings.com, they use the same lower unit design. I just don't know if all the parts are the same.

As for the bang, the motor didn't really "jump" when it happened. My hand was on the tiller and it felt like a detonation. I don't remember the lower unit moving when it happened. It sounded like I'd hit something, but it didn't look like I'd hit something if that makes sense.

Does repairing the clutch dog involve just replacing that part or am I going to need to find a whole new drive gear set? And, as above, will the QD-16 parts fit a QD-15?

 

[dshanks]

Never mind about the water pump kit question. I found the answer.

Still need to know if the clutch dog repair requires replacing the gears too. Or will I not know until I open the lower unit?

 

[dshanks]

I believe I found the reason for poor cooling at high throttle. I pulled the water pump and the impeller looks fine (though I'm replacing it). But the grommet at the top of the pump is split (see picture). My theory is that at low speeds and low water pressure most of the water was going up the water tube. But at high speeds and high water pressure too much water was exiting through the split in the grommet. I have a pump rebuild kit on order.



One more question: When I pulled the lower unit, the water tube pulled down too before detaching from the water pump grommet. I assume this disengaged the top of the tube from whatever it goes into in the head. Am I likely to be able to just push it back into place from below, or am I going to have to tear into the drive shaft housing to put the tube back in place?

 

[dshanks]

Figured the water tube question out. The place where it goes into the head is accessible from the right side of the drive shaft housing. There's a grommet there that has split too. Looks like it's the original one since the protruding part is painted green. I'm hoping I can pull the old grommet out and get the water tube into the new grommet.

Thankfully there's an old OMC dealer about five minutes from my house. I was talking to the parts lady today and she told me they used to have about 50 of these old OMC motors laying around. Said the owner is working toward shutting the business down and gave the old motors away for scrap.

 

[F_R]

RATS!!! Why am I never around when they give that stuff away?

 

[dshanks]

Yeah I know.. The lady's eyes popped when I told her what these things sell for on eBay.