1970 Evinrude 18 hp won't start

[Nicktr23]

I completed a carb rebuild and was getting the motor to run in the barrel. Everything went well testing. I took the motor out and test it at the lake and I believe it overheated? At first I had issue starting the motor, but tweaking with the fuel mixture screw, I was able to get it running. I checked and water was coming out from tell tale, so the pump was working. I was cruising up and down near the dock after 30 minutes. Then I check the water to see if it's coming out from the tell tale and now no water was coming out. The engine did stall at this time. I try to ride back to dock, the engine stalled halfway. I couldn't get the motor to start again. I took it home and checked the impeller and it looks to be in good shape. Reinstall everything back and still cannot get the motor to start. What could be the problem?

 

[oldboat1]

a few guesses -- water tube might not be fully seated in grommet at impeller housing (edge of grommet might be jammed). Impeller pin might have moved out of place (impeller not spinning with shaft). Blockage in the tube or water passage. Thermostat bypass blocked or t.stat sticking closed. Wrong impeller installed. Intake screen blocked.

 

[Nicktr23]

I'll wait for the new impeller to come in and take apart the lower unit again to check. I'm sure it is seated correctly as it was challenging getting the shaft to line up properly. How do i check if the thermostat is in closed position? But will thermostat prevent engine from starting?

 

[RCO]

Check your compression first. If it did overheat to the point of stalling there's a good chance it did some damage.

 

[racerone]

Thermostats normally fail open on those.-----Does spark jump a gap of 5/16", yes or no ?

 

[Nicktr23]

Check your compression first. If it did overheat to the point of stalling there's a good chance it did some damage.

Compression is low. One is 25 psi the other is 75 psi. I remember checking prior to this and the two numbers were low but they were around the same. What next? Remove power head?

 

[Nicktr23]

Check your compression first. If it did overheat to the point of stalling there's a good chance it did some damage.

Compression is low. One is 25 psi the other is 75 psi. I remember checking prior to this and the two numbers were low but they were around the same. What next? Remove power head?

 

[racerone]

Take the cylinder head off for inspection of cylinders and head gasket.

 

[Nicktr23]

Is this It? Came off pretty easy. There's a lot of carbon build up. Looking into the cylinder it looks good? I took some oil and rub along the inner cylinder for lubrication. I notice inside the cylinder there are many small holes and they have little carbon buildup here and there.

 

[racerone]

Were the bolts tight , yes or no ?------Head will be warped and needs to be resurfaced first.-----Then install a new head gasket and test compression again.

 

[Nicktr23]

No bolts was not tight. Is the carbon buildup a concern? There's even carbon buildup on the bolt themselves

 

[oldboat1]

I would just clean up the head cover with some carb cleaner, then resurface and replace it as mentioned. Resurface by rubbing the mating surface on some 400 grit wet/dry sandpaper. Use a perfectly flat surface and move the head around in a figure eight pattern until you get a uniform shine. (If it's badly warped -- can't get the uniform shine -- you may need to have a shop do it for you.) Clean out/scrape out the water passages in the head and in the cylinders. Before putting on the new gasket, carefully clean any pieces of the old gasket from the cylinder mounting surface. Torque to 18 - 20 ft. lbs. -- pattern is circular starting from the center (approx. half torque the first round, then come back and fully tighten).

This may not restore compression, but pretty good chance if the head bolts were loose. Should retorque the bolts after running.

 

[Nicktr23]

I would just clean up the head cover with some carb cleaner, then resurface and replace it as mentioned. Resurface by rubbing the mating surface on some 400 grit wet/dry sandpaper. Use a perfectly flat surface and move the head around in a figure eight pattern until you get a uniform shine. (If it's badly warped -- can't get the uniform shine -- you may need to have a shop do it for you.) Clean out/scrape out the water passages in the head and in the cylinders. Before putting on the new gasket, carefully clean any pieces of the old gasket from the cylinder mounting surface. Torque to 18 - 20 ft. lbs. -- pattern is circular starting from the center (approx. half torque the first round, then come back and fully tighten).

This may not restore compression, but pretty good chance if the head bolts were loose. Should retorque the bolts after running.

I was afraid that it wouldn't restore compression. What else can cause compression drop? I'm replacing the thermostat and gasket at the same time. Will also put in New spark plugs as well. Crossing my fingers. I also have a 1962 Johnson 18hp that just needs a new water impeller, so at least if this doesn't fire up, I still have 1 working motor. But this envirude looks like it's in better condition.

 

[oldboat1]

broken ring, maybe. Would look for serious cylinder wall scoring, or pull off the exhaust cover to see the rings. After some diligence reseating the head cover, though, I think it's got a chance.

 

[Nicktr23]

Receive the cylinder head gasket today and installed it. Also replaced the thermostat, but forgot to order the rubber thermostat seal, so I tried to reuse the old one. I'm not sure if it will make a big difference. Please let me know what the purpose of that rubber seal around the thermostat is. My guess it that it serve to insulate the thermostat? Anyways, I still assembled it together, along with the new thermostat cover gasket. I manage to stripped the threading on one of the three screws holding the thermostat cover in place (found this out when i notice water running down the screw. Was I suppose to use some sort of water sealant on the gasket?
But... the motor to start again. this is when I noticed the water running out of the thermostat plate. I probably have a bad compression tester because I was getting only 35-40 on one cylinder and 60-70 on the other. It did take many pull to get the motor to start. It ran for 30 seconds before I notice the water leak and stopped the engine.
Any suggestion on what to do about the stripped threading? I'm thinking buying bigger bolt anr tap a bigger hole. Also, the thermostat gasket didn't seem to make a good seal For the water. Do you use rtv silicon on the gasket?

 

[oldboat1]

Look around for a head cover from a donor motor. In the meantime, you can try rethreading that t.stat cover bolt with some MarineTex, or thickened epoxy. Put the epoxy in the hole and set the bolt wrapped in some plastic wrap. When the epoxy sets, you should be able to back the bolt out. Clean up the surface and see if the bolt will seat.

The gasket seal there can be difficult. I try to get an oem gasket if I can, and use a little BRP gasket sealer. The rubber gasket for the t.stat unit goes around the flange -- think it's meant to seal, as I don't think metal to metal contact with the flange would affect sensor function. In any case, though, it would seal as well as isolate.

Might try to borrow a compression tester, or get a loaner -- check with another tester.

 

[Nicktr23]

I used some RTV gasket sealant on the oem gasket and put in new thermostat seal. No more leaks from the thermostat housing. The motor runs now.

 

[Nicktr23]

https://youtu.be/fSBnve2-Ta4

I made a clip of the motor running now. Let me know what you think. I adjusted the fuel mixture screw to the best I can. Any richer, it stalls when shifting into forward gear.
Btw, thank you for your inputs.

 

[oldboat1]

Sounds good from here. Guessing the compression is decent -- curious to hear what readings you now get. Should retorque the head bolts now that it's been running (96-120 inch lbs). Good idea to check head temps too (look for maybe 120-140F. 160F would be too hot.)

On idle air/fuel mix -- look for leanest setting where the engine runs smoothly and shifts into gear without stalling. The motor sounds good to me at idle as is, but your comment suggests to me that you are looking for the richest setting where it runs well, rather than the leanest -- though could be a distinction without a difference. Anyway, might review procedure for setting the needle (lean/clockwise until it stalls or lean sneezes, then back out about 1/4 turn richer.)

 

[Nicktr23]

Sounds good from here. Guessing the compression is decent -- curious to hear what readings you now get. Should retorque the head bolts now that it's been running (96-120 inch lbs). Good idea to check head temps too (look for maybe 120-140F. 160F would be too hot.)

On idle air/fuel mix -- look for leanest setting where the engine runs smoothly and shifts into gear without stalling. The motor sounds good to me at idle as is, but your comment suggests to me that you are looking for the richest setting where it runs well, rather than the leanest -- though could be a distinction without a difference. Anyway, might review procedure for setting the needle (lean/clockwise until it stalls or lean sneezes, then back out about 1/4 turn richer.)

Took the motor out to the river yesterday. I was able to to up and down the river a couple of time. Then out of nowhere the motor stop. The flywheel Is stuck. I tried wiggle back and forth, it's stuck. I'm pretty bummed. I opened the cylinder head again and this time see some metal shaving. I believe it will need a new powerhead. Is this something easy to Do? There's currently a power head on eBay for my motor, but before I go and spend more money, I need to be able to remove the old powerhead off and see if it's within my ability. Is there any special tool that is needed? Do I have to remove the flywheel off? Is that even easy to do?