Johnson 35 with intermittent stream before thermostat opens

[chrisgt]

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.

 

[saltchuckmatt]

Does it do this on the water or just on muffs/barrel?

 

[chrisgt]

Does it do this on the water or just on muffs/barrel?

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.

 

[chrisgt]

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?

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

 

[saltchuckmatt]

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.

 

[chrisgt]

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.

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...

 

[airshot]

Saltwater engine ?

 

[chrisgt]

Saltwater engine ?

I use it mostly in fresh water, but i have no idea how it was used for the last 40 years of its life.

 

[airshot]

I use it mostly in fresh water, but i have no idea how it was used for the last 40 years of its life.

Just noticed the corrosion seemed excessive, so my thinking was salt water..

 

[saltchuckmatt]

5 minutes per bolt....pretty sure you could teach us all!

 

[chrisgt]

5 minutes per bolt....pretty sure you could teach us all!

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.

 

[saltchuckmatt]

Tried an induction bolt heater yet?

 

[chrisgt]

Tried an induction bolt heater yet?

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.

 

[Faztbullet]

Since it got hot enough to ping and has cancer ,mostly likely have a head gasket passing compression into cooling system. Compression test only show if cylinder have enough compression to support combustion. The 15hp pic below ran but was low on power like over propped and rough idle. It had 120psi per cylinder but motor is bad. Seen plenty of blown motors with good compression

 

[chrisgt]

This thing runs like a bat out of hell, pushes my 14ft starcraft to 30kts, so I don't think it's blown up. But I don't want it to

 

[cyclops222]

Those pistons tell it has been abused terribly. Run it until it dies
Carry a cell phone that works from anywhere you go to. Carry a pair of correct sized oars. Enjoy the old timer.
Make sure your anchor & line are big & long enough when needed.

 

[saltchuckmatt]

Those pistons tell it has been abused terribly. Run it until it dies
Carry a cell phone that works from anywhere you go to. Carry a pair of correct sized oars. Enjoy the old timer.
Make sure your anchor & line are big & long enough when needed.

You know those pistons are not the original posters engine, right?

 

[cyclops222]

I am taking the 87th Geezer Amendment.

 

[chrisgt]

I pulled the exhaust cover off and miraculously 6 of the bolts didn't break off!
The pistons and cylinder walls and piston skirts/rings look amazing.

Sadly there's no "smoking gun," except for one bolt that was blackened with exhaust, it doesn't seem to have any blown gaskets or holes in the exhaust plate thing.

I really don't want to remove the cylinder head (not sure why, i just don't wanna), but I'm expecting that i'll install new gaskets and have the same problem. Maybe i should pull the power head and do base gaskets also... I really don't like unresolved problems, makes me uncomfortable every second i'm on the water.

 

[chrisgt]

well so... I can't leave things well enough alone, if it isn't perfect i'm not done.
Pulled the cylinder head off (only two bolts on this stupid turd broke, and one bolt hole stripped out...), i think it's a blown headgasket. The gasket looks suspect, it's a bit burned, the lower portion of the bottom head is steam cleaned where i think it was just barely leaking. Caught it before any major damage. Pain in the behind, but I think it'll be 100% when i put it back together.