overheating

[Rich Novak]

1972 omc 225 sterndrive

first test on water I have already cleaned the logs, new thermostat, new water pump.
Nice stream comes out the o/d.

At idle no problem stays at about 175.
anything over 1600 rpm it start overheating, if i bring it back to 1000 rpm it cools down

Thanks, Rich

 

[HT32BSX115]

Re: overheating

1972 omc 225 sterndrive

first test on water I have already cleaned the logs, new thermostat, new water pump.
Nice stream comes out the o/d.

At idle no problem stays at about 175.
anything over 1600 rpm it start overheating, if i bring it back to 1000 rpm it cools down

Thanks, Rich

Howdy Rich.


A marine cooling system usually depends on flow. If the water cannot get in or out, there may not be enough flow to keep the engine cool when running.

Higher power settings require more flow.


If the raw water pump cannot push enough water through the engine because of a restriction some place in the raw water supply you'll get overheats....

OR, If your manifolds, risers, block, (circulating) water pump, are clogged with rust, you may not be able to flow enough water in the engine itself.

There's also the T-stat. If it (or the housing) is clogged with debris or rust, or it's frozen, same problem.

Since you covered some of the above "things", you might have blockage in the things you didn't check. (block, risers, circulating pump, heads, raw water hoses etc)


Regards,


Rick

 

[Rich Novak]

Re: overheating

Howdy Rich.


A marine cooling system usually depends on flow. If the water cannot get in or out, there may not be enough flow to keep the engine cool when running.

Higher power settings require more flow.


If the raw water pump cannot push enough water through the engine because of a restriction some place in the raw water supply you'll get overheats....

OR, If your manifolds, risers, block, (circulating) water pump, are clogged with rust, you may not be able to flow enough water in the engine itself.

There's also the T-stat. If it (or the housing) is clogged with debris or rust, or it's frozen, same problem.

Since you covered some of the above "things", you might have blockage in the things you didn't check. (block, risers, circulating pump, heads, raw water hoses etc)


Regards,


Rick

I don't think it is an internal engine problem I checked most everything hoses ect.
can the impeller in the od cause this problem at higher rpm

Thanks, Rich

 

[southkogs]

Re: overheating

When was the last time the impeller was changed? Electric shift won't pick up water from muffs, and running it on a hose connector bypasses the impeller.

Welcome aboard.

 

[Rich Novak]

Re: overheating

When was the last time the impeller was changed? Electric shift won't pick up water from muffs, and running it on a hose connector bypasses the impeller.

Welcome aboard.

I don't know when the impeller was changed it is a new to me boat .I installed a bypass in the hose leading into the manifold to hook up a garden hose to supply water. ( as per this forum) no muff holes on my 72 225 sterndrive.
Will the impeller work at low rpm and not at higher rpm ?? If so that is probably the problem I still have a nice stream out the drive .

Thanks, Rich

 

[southkogs]

Re: overheating

I would change the impeller. It's simple, and probably needs to be done anyway. It would eliminate the problem of it working at low speed and not at high speed. When my last temp problem happened (sounds similar to yours) it turned out to be my thermostat, but I changed the impeller anyway and it actually did help my waterflow quite a bit.

If you're showing tell tales outta' the drive when you're on the hose, it's not tellin' ya' anything about the impeller - you kinda' bypass the impeller runnin' it in the driveway.

 

[Howard Sterndrive]

Re: overheating

I would replace a section of the hose to the tstat housing with clear hose and watch for exhaust bubbles in the water stream. Greasing the swivel in the drive will help the seal there do it's job of keeping the exh. away from the suction side of the pump.

But if the impeller age is unknown, changing it and greasing the w/p shaft splines is an automatic priority. Weak impeller tends to cause overheats at idle and get better with rpm. Whereas issues of the impeller sucking exhaust tend to be most prevalent under load at higher rpm.

 

[Rich Novak]

Re: overheating

I would replace a section of the hose to the tstat housing with clear hose and watch for exhaust bubbles in the water stream. Greasing the swivel in the drive will help the seal there do it's job of keeping the exh. away from the suction side of the pump.

But if the impeller age is unknown, changing it and greasing the w/p shaft splines is an automatic priority. Weak impeller tends to cause overheats at idle and get better with rpm. Whereas issues of the impeller sucking exhaust tend to be most prevalent under load at higher rpm.

I think the impeller is sucking exhaust , the impeller doesn't look bad.Does the grease really do the job , someone told me the upper pump housing needs to be replaced to keep the seal tight.300 $ isn't in the budget.
Thanks, Rich

 

[southkogs]

Re: overheating

I would change the impeller using the kit, and grease the swivel like Howard suggested. It does help with the system sucking up exhaust. If the "someone" who told you about the upper pump housing was a marine mechanic who looked at your boat (specifically) then maybe you need to look at changing the housing. If the "someone" was a guy who has/had/heard about OMC engines ... nevermind it for now.

 

[Howard Sterndrive]

Re: overheating

I think the grease works when there is an issue with the seal to some extent. If the seal area and everything is new, I don't know that the grease would be needed for anything besides smooth steering, but I know it has cured overheating stringers before.

 

[Boomyal]

Re: overheating

Well, one of the manuals that I have warns about 'servicing' the swivel housing when you are doing an impeller change and that a failure to do so "could' cause exhaust gas leakage into the impeller housing, keeping the impeller from working.

I should go back and find that and re-read it.

 

[Rich Novak]

Re: overheating

Well, one of the manuals that I have warns about 'servicing' the swivel housing when you are doing an impeller change and that a failure to do so "could' cause exhaust gas leakage into the impeller housing, keeping the impeller from working.

I should go back and find that and re-read it.

Thanks everyone for your input. I changed the impeller using the kit , I think some o rings were missing from the last time someone got into it.
any way all o rings are in place and the swivel housing well greased so hopefully I will work fine the next time in the water.

Thanks, again, Rich

 

[THE BEEF]

Re: overheating

Be there, like someone said give the swivel bearing about 12 shots of grease and see if it solves your O/H problem.
I had the same issue and I tried it, it works. A OMC mechanic told me about this.
Later I tore it down and replaced the seals, That was 4 years ago, still going strong and no problems.
Beef