One cylinder running hotter than other

[willinokc]

Engine is a 1960 40 hp Johnson, posted a couple times now. Newbie so I can use all the help I can get.

Could a missing thermostat make the top cylinder run hotter, or even over heat, while the lower looks ok?

Had an overheating prob so checked the thermostat, found there wasn't one. Ordered one. Changed the impellor already so thought I'ld make sure there wasn't a blockage internally so pulled the head cover off. No blockage that I could find, blew everything out w/ compressed air. One piston is wet w/ oil (lower) top is is crusty/dry.

What could cause this?

BTW, rebuilt carb, changed points, condensers, coils and plug wires already. Seems like running into one prob after another with this motor. Guess I'm learning a lot though.

 

[bktheking]

Re: One cylinder running hotter than other

That thing pumping lots of water out the rear of the exhaust leg? It should have a stat in it, replace it and then check it, it regulates temperature and is in there for a reason, nes pas?

 

[willinokc]

Re: One cylinder running hotter than other

Just for the record, I wasn't the one who pulled the thermostat. Didn't know about it until I started checking on things.

 

[bktheking]

Re: One cylinder running hotter than other

Which is fine, I didn't think you owned it since new and forgot you pulled it. Picking up used motors that don't run right is like a puzzle, I tell people if you were good at puzzles as a kid then fixing something mechanical should come natural.

 

[willinokc]

Re: One cylinder running hotter than other

My experience with this motor has been more of a jack in the box than a puzzle, lots of surprises. I get your meaning though.

Didn't seem like a ton of water out the back, but some. Read you can run just a bit w/o that stat cover on to make sure impeller is pushing water. Plan on doing that next.

 

[bktheking]

Re: One cylinder running hotter than other

Me and my neighbour picked up a 64 this summer. It wasn't pumping when we started it. I pulled it apart and put a new pump in it. At idle water sprays out the hole in the exhaust leg at a good rate. It's not a garden hose type flow mind you but a consistent good pressure spray. And it did have the stat and I did test it in boiling water with a temp probe, opened at 140 like it said it should. Put is all back together and it ran perfect.

Here's a vid of it running

http://www.youtube.com/cpgixxer#p/u/7/O1dF-GtP8NE

Compare yours to this thing, btw I read 60-61 were the years to avoid, 63+ were totally redesigned with new powerheads.

 

[willinokc]

Re: One cylinder running hotter than other

Nope, my spray isn't anything that strong. More of a mist. w/o the stat in it I would think it would be even stronger. I guess I need to pull it and look again at the pump and water tubes.

As far as the 60' being something to watch out for, it came w/ the boat. Got the motor, boat and trailer for under $500 so I can't complain too much... yet. Don't have too much into the motor but have changed the condensers, points, coils, plug wires and impeller so it's starting to tally up.

Where did you get a new pump? Does iBoats have em? Going to check for blockages and make sure everythings lining up first but might need to go that route.

 

[Knightgang]

Re: One cylinder running hotter than other

I do not think your original issue (one cylinder hotter than the other) has anything to do with coolant. You said one cylinder is wet and the other is crusty dry. I suspect that the crusty dry one is the one running hotter... Sounds to me like the dry, crusty, hotter one is running lean which is why it is running hotter...

You have rebuilt the carbs already, was that before or after the inspection or the cylinders? Are you sure you got the jet passages clear.

Also, are both carbs adjusted equally? Or does it only have one carb??? These are the best ideas I can come up with right now...

 

[bktheking]

Re: One cylinder running hotter than other

Local dealer here in town , $38 for just the impeller!!! but it was OMC not aftermarket. We had the stat out and the spray was pretty much the same. You may have a blockage or the pump isn't in properly or one of the tubes isn't in right. A mist isn't circulating water properly, I got my 7.5 back together and it's just a mist and the thing is bloody hot, I know it isn't pumping properly, same as yours, i've missed something.

 

[bktheking]

Re: One cylinder running hotter than other

Also, are both carbs adjusted equally? Or does it only have one carb??? These are the best ideas I can come up with right now...

One carb on this motor, if he's just getting mist out of the exhaust in the leg it's overheating plain and simple, I suspect that's why one of the plugs is not wet, that cylinder isn't getting cooled.


Oh ya and these motors will NOT run on muffs, water has to be at least half way up the leg to pump properly.

 

[willinokc]

Re: One cylinder running hotter than other

Checked heads after carb rebuild but also after I noticed it's running hot. I think it's time to pull lower unit and do an inspection of the pump and tubes tomorrow night. Will let you know how that goes.

BTW, I am having carb issues and have replaced hoses to see if that helps. Haven't run yet because of the other stuff. Not ruling that out as a contributing factor but I do think that I've got an overheating issue.

Hopefully I can get it squared away. I should be posting tomorrow w/ some results. Keep you fingers crossed for me.

 

[bktheking]

Re: One cylinder running hotter than other

Was there a gasket under the pump? When I pulled the one off that I did there was a gasket that was in really rough shape. When I went into the dealer they looked it up in an old OMC parts book, they told me there was no gasket to replace, I left it out, I think it may of had something to do with the poor flow.

 

[lindy46]

Re: One cylinder running hotter than other

Make sure the pin/key which drives the impeller is in place on the driveshaft.

 

[willinokc]

Re: One cylinder running hotter than other

No gasket under the impeller housing. I might try using some liquid gasket to give it a better seal.

Checked the pin when I installed the impeller and made sure the impeller would spin when the shaft spun. Pretty sure it's seated properly.

 

[bktheking]

Re: One cylinder running hotter than other

No gasket needed, don't bother.

 

[willinokc]

Re: One cylinder running hotter than other

She's pumping water again. Not sure what I fixed. Just went through the system making sure all pipes were clear, took the water pump apart, made sure the impeller was in right, thoroughly cleaned all mating surfaces, checked the intake to make sure it was clear and then methodically put everything back together again. I've got a good steady stream now, just what I would expect since I'm still missing the thermostat. Getting that Monday, along w/ a fuel pump kit. I think we're getting there. Thanks for the help!

 

[bktheking]

Re: One cylinder running hotter than other

The vid I sent you was a cold start, it started pumping water almost immediately, stat in or out shouldn't effect the spray. But put at stat in it cause it has one.

 

[willinokc]

Re: One cylinder running hotter than other

The vid I sent you was a cold start, it started pumping water almost immediately, stat in or out shouldn't effect the spray. But put at stat in it cause it has one.

I put the stat in and engine runs A LOT cooler. My flow out the exhaust is now just a spray though. Not as heavy as your vid. I even took the stat cover off to double check and she's pumping water. If you hold your hand in front of your exhaust it gets wet and dripping immediately and it is running cooler so I'm good, right?

It pretty much pours out of there without the stat in.

 

[tashasdaddy]

Re: One cylinder running hotter than other

with out a Tstat the water flows too fast, the convection does not happen, and the motor runs hot. if you have droplets or mist out the exhaust relief port, you are fine. most do not put out a stream of sorts until running fast.