overheat but got water

[fishfeatures]

took my brothers 91 70hp out, and after a while of pottering about to and from various fishing spots, i decided to take it for a spin. Was at WOT for 2 mins and it started to splutter badly so i throttled back. Went to power up but it just wouldn't let me and it started spluttering and sounding real rough. It was peeing a good stream so i ruled out a cooling prob. I slowly made my way back to dock and guessed it had gone into SLOW.

Back at the dock it's clear it had overheated as the heat from the motor was unreal.

If it was peeing water how can it over heat? it's used on fresh water so i can't see the passageways being blocked up.
Now he has just done the cooling mod to it so surely that hasn't an effect on it.
I have no temp gun and his buzzer didn't go off ( tested this and it's shot)...

 

[sutor623]

Re: overheat but got water

Son of a $%#&!!!! Man you probably have a bad thermostat. Check compression on the poor old girl, and if all is well get a new thermostat in her!!!! This is one of the reasons why I HATE that Jonnyrude put the thermostats AFTER the telltale hole.

 

[fishfeatures]

Re: overheat but got water

Son of a $%#&!!!! Man you probably have a bad thermostat. Check compression on the poor old girl, and if all is well get a new thermostat in her!!!! This is one of the reasons why I HATE that Jonnyrude put the thermostats AFTER the telltale hole.

Ok Compression is ok thank god... now I always thought that the telltale was after the stat.....
I'll buy a new stat for it and see if it helps,and mention to him about the horn..... i think i'll keep the overheat quiet for now..:decision:
I'll break it to him over a few beers at the weekend

 

[sutor623]

Re: overheat but got water

Ok Compression is ok thank god... now I always thought that the telltale was after the stat.....

Glad to hear about compression. And yes it would seem as if the telltale would be AFTER the stat, but that is not the case. Another way to confirm that (I not having actual experience with that year 70hp) would be to answer this: Does the tell tale flow just after starting the motor, or does it take a few minutes to flow water? More than likely it flows immediately, meaning that it is flowing while the stat is closed, indicating that the telltale is BEFORE the stat.

If you are ansy, you could always pull the stat and try running it without (temporarily) to see if it fixes the problem.

 

[fishfeatures]

Re: overheat but got water

water starts to come from the tell tale maybe 30 secs or so after initial start up, but probably filling the block i reckon.

I'll run the motor for 15-20 mins with no stat tomorrow and see if the issues arises again.

 

[sutor623]

Re: overheat but got water

Yep that is def in line before the stat.

Cool let me know how it goes. Be careful not to snap a bolt head when pulling the stat cover. Try an not ruin the gasket so it doesn't leak during the test run. And do not rev the motor past 1500-2000 Rpms on muffs.

 

[captk]

Re: overheat but got water

I am thinking that the water pump will not push enough water at WOT. drop the gearcase and do a complete waterpump repacement. also there is a seal at the top of the water tube that will melt when overheated and cause this problem too. that requires removal of the power head to repair. good luck Bill

 

[Willyclay]

Re: overheat but got water

That year/model motor has a design flaw in the cooling system that allows air to be trapped in the upper half of the system that can cause it to overheat. OMC issued Service Bulletin No. 2276 Rev.1 in April, 1994 with a recommended modification to the telltale installation. Probably worth reading in the link below from the FAQ's before replacing other parts. Good luck!

http://forums.iboats.com/engine-fre...johnson-evinrude-adding-tell-tale-222677.html

 

[toddschubert]

Re: overheat but got water

Not positive it does but that motor may have water deflectors in the water jacket. Need to remove heads to get to them. Not that big of deal. They are little rubber tubes that flatten and close with time. They are supposed to restrict but not stop water flow around. Cyl head and force it around the other way. It's a possibility

 

[fishfeatures]

Re: overheat but got water

That year/model motor has a design flaw in the cooling system that allows air to be trapped in the upper half of the system that can cause it to overheat. OMC issued Service Bulletin No. 2276 Rev.1 in April, 1994 with a recommended modification to the telltale installation. Probably worth reading in the link below from the FAQ's before replacing other parts. Good luck!

http://forums.iboats.com/engine-fre...johnson-evinrude-adding-tell-tale-222677.html

as i mentioned is first post, he carried out the mod not so long ago.

 

[fishfeatures]

Re: overheat but got water

I am thinking that the water pump will not push enough water at WOT. drop the gearcase and do a complete waterpump repacement. also there is a seal at the top of the water tube that will melt when overheated and cause this problem too. that requires removal of the power head to repair. good luck Bill

i think you cracked it, i hooked up an old pressure gauge i had lying about, and at idle it registered 1 psi and at WOT it was 6.

With no stat in and with this pressure, it overheated, so i reckon gauge is good and impeller isn't


i'll drop the lower and replace the impeller ,it's an easy fix and hopefully he wont look for it back for a day or two and the new one will sort the prob

thanks guys..

 

[fishfeatures]

Re: overheat but got water

ok now i'm in trouble... new waterpump kit ddin't solve the problem, am still getting 1-5 psi max. I blew air into the outlet at the top of the block and i blew air into the tube in the lower unit. I also whipped off the head and can't see any issues there. Now i have a 1990 60hp johnson and I also have a spare lower unit for this. So i swopped this on his 70hp and I am still getting the same result.

I need help troubleshooting the cooling system, where do i go to next.. any help at all please guys.

I think i'll own up to the brother tomorrow, better he knows at this stage i think..

 

[fishfeatures]

Re: overheat but got water

ok just to close off the thread, we have success!! I pulled the lower unit and took out the stat. I then hooked up the garden hose to the copper water pick up tube and I must have cleared a blockage. Once all flushed out and put back together, it ran like a dream again (phew)... so must ahve picked up a blockage somehow in the cooling system, dunno how but it's going great and that's all that matters.

 

[fishfeatures]

Re: overheat but got water

:rockon:

 

[sutor623]

Re: overheat but got water

:cheer2:

 

[Willyclay]

Re: overheat but got water

Attaboy, it's usually the simple stuff. You just have to find it!