57 johnson 5.5 replaced everything still overheating..

[floatingwoody2006]

Hello all. I have this 57 5.5 and i replaced impeller, gaskets, o-rings, and drive shaft seals. The head still gets hot to the touch after 20 seconds or so. Too hot to make me want to keep running it. I have had the lower off 3 times.. And it's a roal pain having to remove the power head every time. I did replace the powerhead base gasket as well. It is spraying out the exhaust, but maybe only 75% of what i think it should. I hit the entire cooling passaes with compressed air, and it is very clear. I am stumped i guess..Only thing i can maybe think of is..could a bad head gasket cause this? No water on plugs, and compression is good. Anything other than a plugged cooling passage or impeller that might cause this? The reason i changed the impeller was that it was running mint, but stopped spraying for whatever reason..When i removed it, was spongy, and in decent shape. Thanks iin advance....oh forgot to mention, before putting the powerhead on for the 3'rd time, i spun it in a barrel with my drill, and got water up the tube ok..

 

[EN2]

Re: 57 johnson 5.5 replaced everything still overheating..

Is the water pump tube entering the waterpump? Make sure the tube go onto the midsection first. Also the rubber grommets for both end of the tube should be new.

 

[floatingwoody2006]

Re: 57 johnson 5.5 replaced everything still overheating..

everything's kosher as far as seals go..That's what's so perplexing. I have done a bunch of these..it's an unusual situation..

 

[lindy46]

Re: 57 johnson 5.5 replaced everything still overheating..

Try sprinkling some water on the block when you think it is getting too hot - see if it sizzles and boils off. If it doesn't sizzle, you should be all right.

 

[samo_ott]

Re: 57 johnson 5.5 replaced everything still overheating..

Is it the head that is hot or the exhaust cover? Cause the older 5.5's did not have water cooled exhaust cover. But if it's the head (but it sure sounds like you know what you're talking about) it sure sounds like you have done it all...

 

[floatingwoody2006]

Re: 57 johnson 5.5 replaced everything still overheating..

Thanks Samo..It's definately the head that is getting hot. Not enough to sizzle water, because i don't allow it to get that hot. It's just funny that the water is travelling the tube to the powerhead, and the passages in the powerhead are clear. Compressed air shoots right thru all of them. Yet, when it is put together, the exhaust does not spray correctly. Just not cooling. Hate to sell it because it's a classic good runner, but i don't really want to keep taking it apart over and over. Thanks.

 

[R.Johnson]

Re: 57 johnson 5.5 replaced everything still overheating..

Dis you replace the whole pump, or just the impellor? When you replaced,the exhaust to powerhead gasket. Did take the old gasker, or model nimber with you? There's a difference in these gasket/s

 

[Sea18Horse]

Re: 57 johnson 5.5 replaced everything still overheating..

What brand of impeller did you buy? I have heard of some people having these kinds of issues with aftermarket ones. How did the housing look? I like to get a complete water pump assembly the first time so I know where I'm at.

I'm thinking it might be a good idea to invest in one of those infrared temperature probes. I understand Harbor freight carries one for not a lot of money. That way you'd know exactly what the temp is. And remember the head itself is often not water cooled. Around the edges yeah but not towards the center. Done to allow the spark plug to stay hot enough to burn off deposits. Not sure if this is the case with this model but something to keep in mind. Good luck!

Cheers...............Todd

 

[floatingwoody2006]

Re: 57 johnson 5.5 replaced everything still overheating..

Thanks Guys..I only replaced the impeller with a sierra replacement. The powerhead gasket #'s matched the sierra #'s i needed. ordered online. the housing looked good with the metal plate not too worn. I think i will try tonight to run it for a bit in the barrel, and if anything looks like it is real hot, off it all comes again, and i will do the entire Housing if i can find it. what a pain though..

 

[tmcalavy]

Re: 57 johnson 5.5 replaced everything still overheating..

Make sure all the passages into and out of the pump are clear and that the impeller is keyed to the shaft...those little keys wear out, too.

 

[Finnish genius]

Re: 57 johnson 5.5 replaced everything still overheating..

Have you tried it on the boat in the water or just the barrel?. One of mine was ok on boat but tank ran rather hot in tank. Ken

 

[OptsyEagle]

Re: 57 johnson 5.5 replaced everything still overheating..

I can't remember when they decided to add a thermostat to these motors but I think it was after 1957. In any event, if right above your cylinder head is a triangular piece with three screws in it, then you have a thermostat and I would want to make sure it has not failed closed.

If you do not have a thermostat, make sure your powerhead to exhaust gasket is correct. Sierra 18-2901 is for models with a thermostat and 18-2894 is for models without a thermostat. Both will appear to be the same and fit on your motor. I am not sure if the wrong gasket would block any water but they obviously made a different gasket for a reason.

 

[post5racing]

Re: 57 johnson 5.5 replaced everything still overheating..

Hello all. I have this 57 5.5 and i replaced impeller, gaskets, o-rings, and drive shaft seals. The head still gets hot to the touch after 20 seconds or so. Too hot to make me want to keep running it. I have had the lower off 3 times.. And it's a roal pain having to remove the power head every time. I did replace the powerhead base gasket as well. It is spraying out the exhaust, but maybe only 75% of what i think it should. I hit the entire cooling passaes with compressed air, and it is very clear. I am stumped i guess..Only thing i can maybe think of is..could a bad head gasket cause this? No water on plugs, and compression is good. Anything other than a plugged cooling passage or impeller that might cause this? The reason i changed the impeller was that it was running mint, but stopped spraying for whatever reason..When i removed it, was spongy, and in decent shape. Thanks iin advance....oh forgot to mention, before putting the powerhead on for the 3'rd time, i spun it in a barrel with my drill, and got water up the tube ok..

Hey did you ever figure out your problem? i have a 58 thats doin the same thing...

 

[goegr]

Re: 57 johnson 5.5 replaced everything still overheating..

If everything looks kosher, check that the impeller key was installed (the little bit of metal that makes the impeller go round). If that is ok, check the little hole on top of the water pump housing. It is near the shaft and if it is blocked, the pump may not prime properly.

 

[goegr]

Re: 57 johnson 5.5 replaced everything still overheating..

If everything looks kosher, check that the impeller key was installed (the little bit of metal that makes the impeller go round). If that is ok, check the little hole on top of the water pump housing. It is near the shaft and if it is blocked, the pump may not prime properly.

 

[floatingwoody2006]

Re: 57 johnson 5.5 replaced everything still overheating..

I believe i was shipped the wrong base gasket version, but i got so sick of removing and replacing the head, i sold it for 200 bucks. I loved the motor dearly, but i did not have time for it. Good luck.