Johnson 35 with intermittent stream before thermostat opens

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chrisgt

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I have a 1981 johnson 35 with a weird problem.
Here is some history: The thermostat broke in half causing the engine to overheat a bit (i heard it pinging and shut it down before it seized or anything bad). I changed the thermostat, cleaned the bore so it can spring open and bypass at high RPM, etc. Using a thermal gun it never gets over about 145 degrees at the housing so I think that's working correctly.

Now for the strange issue:
Until the thermostat opens the telltale just spits water as if the water pump is bad (it's not).
If I rev the engine over 3000rpm or whatever it takes to open the spring it also sprays a constant stream.

Once the thermostat opens it has a perfectly steady and healthy stream; if I remove the hose from the exhaust housing it shoots a jet of water 5 feet, so I think my water pump is fine (i replaced it anyway, it's not the problem).
The exhaust housing cover thing has the bottom aft bolt broken off (i guess due to enough thermal expansion and rust?) so I'm wondering if this is caused by a leak in the exhaust gaskets or center plate?
I don't get any water in the bottom cylinder and it's not steam cleaned.
I don't THINK it's a blown headgasket, both cylinders have 125psi of compression and it has no running issues.

I just wanted some input before I go to take that cover off. Replacing the thermostat meant extracting half a dozen broken bolts and I'm assuming i'm in for the same treat with the exhaust gaskets.
 
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chrisgt

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saltchuckmatt said:
Does it do this on the water or just on muffs/barrel?
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Does it out on the water. If i stop and fish for a while it'll squirt and spurt for a minute, the thermostat opens, and it returns to a normal stream.

It does the exact same thing on the ground with muffs, too. but I know those have their own issues so I always confirm these things on the water.
 
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chrisgt

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This bottom bolt here (which looks like so much fun to deal with) has snapped itself off, which is why i wonder if there's somehow exhaust sneaking into the cooling water, then since there's more flow out the top of the head once the thermostat opens (or the poppet allows it to open), it overcomes the exhaust pressure?

7QbySEz.jpg


I had all the bottom bolts break off doing the thermostat, of course it's always the fun ones to get to...
 
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saltchuckmatt

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Yeah, you have outboard cancer and it's getting air from somewhere. Run it until it implodes or buy a used dead motor and steal the parts.
 
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chrisgt

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saltchuckmatt said:
Yeah, you have outboard cancer and it's getting air from somewhere. Run it until it implodes or buy a used dead motor and steal the parts.
Click to expand...
heh yea... that's kinda how I feel about it. Doesn't overheat and works fine once the thermostat is open, there isn't much season left so maybe i'll take it apart this winter.
I only spent about 5 minutes on each broken bolt doing the the thermostat, so hopefully it isn't worse than that one. This thing has been a bit of a turd, but it keeps on working, so...
 
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chrisgt

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saltchuckmatt said:
5 minutes per bolt....pretty sure you could teach us all!😆🤣
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Crank the mig welder up hot enough to melt the bolt off flush with the surface. Turn the welder down a bit and weld blobs onto the stump. Immediately hit it with wd40 (or whatever) and twist it out with vise grips. Works almost every time without damaging the threads.

Pro tip if you have a bunch to do: Start with the bottom and work your way up otherwise wd40 runs down onto the ones you still need to do, then you clean it with brake clean and light the thing on fire next time you strike an arc.

I live in the northeast and work on a lost of rusty junk, so broken bolts on an outboard aren't anything too exciting for me.
 
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chrisgt

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saltchuckmatt said:
Tried an induction bolt heater yet?
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I have and those work in some cases. If you're working on aluminum and can get the heater coil around the boss where the threads are you can often free it up, but just heating the bolt head usually doesn't do anything (besides round the head off because you got it too hot...). The reason you melt the stump right up to the aluminum surface is to get heat into the bolt. When you weld blobs to the bolt you have the thing extremely hot, wd40 both shrinks the bolt and gets sucked down the threads through capillary action to lubricate them on the way out.

Or use pb blaster or kroil or whatever weasel p1ss* works for you.
*I worked at a small town mechanic shop and this is what the grumpy old owner called any kind of spray stuff in a can.
 
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