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Strange overheat issues on 86 150hp Evinrude

S

Smgbad

Member
Just went outside after work today to add rtv sealant to both hermostat housing gaskets to stop the leaks from where I installed them without it last week. When I first got the boat a free weeks ago, I had found that someone had removed the white plastic check valve on one side and the other was melted, and thermostats were also removed completely. The check valve relief holes in the housing were plugged and sealed with flex seal... I had just finished adding them back in with all brand new parts.

Well... I got them in with the rtv sealant and now after a few minutes of running, steam started coming from the water jacket gasket and then out of the check valve hole like a tea kettle that's whistling letting you know it's ready. I stopped the engine and took the housing back off. The white plastic check valve poppet is completely melted to the spring. It was brand new... Thermostat was open and it closed as it cooled off.

Tried putting it back together without the check valve and it started spewing super hot water from the check valve hole once started. What could be causing this to happen? Should I just put it back the way it was with no tstats or check valves?

Also worth noting is I just sourced a new old stock temp sensor for it as both of the ones it had when I got it were dry rotted/crumbing and nonfunctional.

Would running it without the tstats and check valves really be a horrible thing if I don't really care about gas mileage?
 
Rwbutler said:
Are you running on a hose or in the water?
Have you looked at waterpump?
Please post compression numbers.
Click to expand...

Running on a hose. Was told the Impeller is brand new. The previous owner had just put a brand new lower end on it before selling it. Getting strong stream from pee hole, although it was steaming when I shut it all off last night. Didn't run too terribly rough, but I do believe it overheated. Dont have my new compression tester in yet. Maybe I used too much rtv? I applied a good thick layer on both sides all around the gasket. COuld that have blocked the tstat water path in some way? It was open when I pulled it right afterwards.
 
Rwbutler said:
Sometimes they need more than just an impeller. Post compression numbers. Inspect waterpump.
Click to expand...

Will inspect the water pump later this evening. When I bought this boat, the thermostat screws were stuck in place and took some work to get out without breaking them... Because of that, I'm thinking this motor has been run for quite some time with no check valves or t-stats. I'm fairly new to these engines... Since my issues only seem to arise when the t-stats and check valves are installed, can I just remove them entirely like it was before? I'm buying a replacement overheat sensor to warn me of overheats, but if I'm not running it for very long periods of time (maybe 10-15 minutes at a time), would that probably be alright? I have a feeling thats why the previous owner removed them as they keep melting.
 
Smgbad said:
Will inspect the water pump later this evening. When I bought this boat, the thermostat screws were stuck in place and took some work to get out without breaking them... Because of that, I'm thinking this motor has been run for quite some time with no check valves or t-stats. I'm fairly new to these engines... Since my issues only seem to arise when the t-stats and check valves are installed, can I just remove them entirely like it was before? I'm buying a replacement overheat sensor to warn me of overheats, but if I'm not running it for very long periods of time (maybe 10-15 minutes at a time), would that probably be alright? I have a feeling thats why the previous owner removed them as they keep melting.
Click to expand...
They were not put thier to melt,they are thier to control water press and your water is too hot. Please post compression numbers before we go any farther.
 
Rwbutler said:
They were not put thier to melt,they are thier to control water press and your water is too hot. Please post compression numbers before we go any farther.
Click to expand...

GOing to be trying to take the compression readings tonight. Made a make-shift remote start. Do you take all the plugs out to do it, or one at a time. Seeing instructionals that go both way on it... From what I can tell I just disconnect the gas, take out all plugs, and test one cyl at a time.
 
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Smgbad said:
GOing to be trying to take the compression readings tonight. Made a make-shift remote start. Do you take all the plugs out to do it, or one at a time. Seeing instructionals that go both way on it... From what I can tell I just disconnect the gas, take out all plugs, and test one cyl at a time.
Click to expand...
Correct....
 
In my workshop that motor would come apart for rebuild.----Those readings are taken with a gauge that is a joke or the motor is junk.
 
racerone said:
In my workshop that motor would come apart for rebuild.----Those readings are taken with a gauge that is a joke or the motor is junk.
Click to expand...

Do you think if I replace the Head gaskets on each side and possibly the water jacket gaskets it would get better compression? Is all i have to do remove the plugs, remove tstats and check valves, remove the water jacket bolts and head gasket bolts, and scrape/replace gasket for head and water jacket cover, inspect/replace deflectors, tighten everything back down?

Also of that is correct, what issues might I run into? I was going to put Rust Buster on the bolts for a day or two before trying to get them off.

But if that won't help compression, it's probably not worth all that wrench turning. I know thats.probably why it's overheating, but Could low compression have something to do with why it takes a while to start until after the first time?
 
So in order to pull the heads (never done this before), I'm ordering 2 new water jacket gaskets, 2 new cyl head gaskets, and a new t-stat kit with new check valves and gaskets. I also have about 6 feet of 3/8" hose to make new deflectors up if they look bad.

Is that all I should need to pull and inspect the heads? My current head gaskets appear to be crumbling in several places around the outline of where you can see them sandwiched in place, so if pulling the heads it just made sense to go ahead and replace them.

Also, upon putting it all back together, can someone tell me the tightening sequence if there is one?
 
racerone said:
I would not order any part until after you have confirmed that it is worthwhile doing.
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Understood... I just need to know if those parts are all that I'd likely need when putting the heads and such back on after inspecting the piston heads and cyl walls? Even if it there is an issue internally after I get it back together, if I go through all the hassle to take the water jacket and heads off with all those stuck bolts, I at least want to put them back on correctly torqued and with the gaskets refreshed. That should at least help with the low compression issue as I'm only supposed to be at 90-95 per cyl anyways (it's a low compression model). I DID see some water bubbling and kightly spewing out right in the area of the head gasket where the cyl is only showing 50psi. I understand there may be some wear to the internals if it's been run like this a long time, but I figured I'd start with just simply refreshing the heads cover gaskets when I take them off to see everything else. It runs too good once running to have reason to believe it has anything catastrophic going on to were I would want to just junk it instead of getting the rest of its life out of it.

So are the 2 sets of gaskets and new tstat kits w/ relief valves all that I'd need?
 
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Let's do this instead.pull the intake bypass cover off the cylinder with the lowest compression.so you can inspect piston and rings in this "good running" engine. Need one 307133 gasket.
 
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