89 OMC 5.0 over heating

[travis sparrow]

Hello I'm having trouble with my engine over heating also getting it winterized. so a little history my boat never stay's in the water it is always taken out after each use. 2 years ago I was floating in a cove with some friends and drained my batteries listing to the radio. when we went to jump it up I had to crank it several times to start it but it finally started. heading back to the marina it over heated and shut down. I then found that my impeller was shot. I replaced it and the housing all at the same time. put it on muffs it would not pick up water unless I was squeezing the muffs tight against the out drive which had never been a problem before. I then decided to put it in the water and it still wouldn't pick up water unless I ran the RPM's up high a few times then it would pick up and run fine. then it would be hit and miss when I would run the boat then come back to an idle if it would continue to pump or start over heating again. but I made it through that year when I went to winterize it that year like I always do. I couldn't get it to take the antifreeze though my Muffs like it normally would so I had to drain and feel through the water neck. this year I had the same problem while its on muffs but it seems to run without over heating as much when it's in the water it still does some but not near as much. I have checked everything that I can think of I need some help figuring this out. why cant I run it on muffs like I always was able to before I over heated it that first time and why does it over heat some times at an ideal in the water?

 

[Lou C]

If the impeller was shot did you look to see if there were bits of the old impeller in the P/S cooler on the back of the engine (it's in line with the raw water intake hose that goes up to the thermostat housing) and the thermostat housing itself?
The other thing that can happen is that the oring on the Cobra impeller housing can shift out of position when you are installing it and cause it to suck air and not prime when running on the muffs. I use a sticky grease like OMC triple guard to hold that oring in place when installing the impeller housing.
A test for this is to leave that plastic cover off when you run the boat the first time after replacing the impeller. There should be no water leaking around the impeller housing when the water is on and the engine is running, if there is that oring is not in correctly and may allow it to suck air.

 

[travis sparrow]

If the impeller was shot did you look to see if there were bits of the old impeller in the P/S cooler on the back of the engine (it's in line with the raw water intake hose that goes up to the thermostat housing) and the thermostat housing itself?
The other thing that can happen is that the oring on the Cobra impeller housing can shift out of position when you are installing it and cause it to suck air and not prime when running on the muffs. I use a sticky grease like OMC triple guard to hold that oring in place when installing the impeller housing.
A test for this is to leave that plastic cover off when you run the boat the first time after replacing the impeller. There should be no water leaking around the impeller housing when the water is on and the engine is running, if there is that oring is not in correctly and may allow it to suck air.

thanks for the reply but unfortunately i have checked all those things. i have even went as far as putting silicone around the base of the water housing to insure the could be no air being pulled in. i have flushed from the engine back and from the outdrive to the engine i have taken the cooler off check all of that it was clean.

 

[stresspoint]

had a little 15 jonno that had a split in the water tube that goes into the impeller housing that would do the same thing .

 

[travis sparrow]

had a little 15 jonno that had a split in the water tube that goes into the impeller housing that would do the same thing .

I will have to look into that I was unaware that there was a tube that went from the intake up to the impeller housing I thought it was just a water jacket made from the out drive case.

 

[Lou C]

There are actually 2 grommets for the water tube that seal it to the upper & lower gear case housings. To change them you have to split the upper & lower gear housings. If you have a real bad overheat these grommets can get softened and may not seal.

A way to tell is to remove the impeller housing and hook up your muffs, turn on the water and you should see water spurt out of one of the openings in the impeller housing.
BTW, I have found that the best muffs are the Merc/Quicksilver ones with the round cups and metal clamp rod.
On boats kept in the water you can get growth inside the water intakes on that plastic screen, I had a chronic problem with this, and had to finally remove that screen so I can clean out the water intakes every so often.

LOWER GEARCASE - STANDARD (R.H.) ROTATION - 1989 Stern Drive 5 502APRMED | Crowley Marine

View parts diagrams and shop online for LOWER GEARCASE - STANDARD (R.H.) ROTATION parts, 1989 Stern Drive 5 502APRMED. Offering discount prices on OEM parts for over 50 years. FAST $4.95 shipping available.

www.crowleymarine.com

part #75 is the grommet

 

[stresspoint]

I will have to look into that I was unaware that there was a tube that went from the intake up to the impeller housing I thought it was just a water jacket made from the out drive case.

my post was meant to be an example of where the air leak could be.
an air leak anywhere between the water pump and the motor will not allow proper water flow.

i have had cracked impeller housings act the same as well , "so along those lines " may also be worth investigating whilst the gear box is removed.