Tohatsu 18hp dies under load

[Sea Rider]

Re: Tohatsu 18hp dies under load

Althouh head is near inmaculate clean pistons and crankcase gasket area are not so, with a cutter remove old gasket pieces leftovers, with thin metal sandpaper polish crankcase and head surfaces smooth to touch. Take advantage to decarbon both pistons, move flywheel untill both pistons are alighned at same height, place them at vertical position, get yourself a can of Power Tuner, Carbon Guard and spray an overdosis of it on top pistons let soak for 30 minutes, with toothbrush brush off, repeat several times if needed.

Clean all bolts threads and slight grease them, place new head gasket and follow torque secuence, torque untill all bolts are hand seated, then in 3 increments of 10 NM each time torque untill you reach 30NM. If thermo looks old and rusted change it along with thermo gasket that breaks when removing upper cap. Assume you have bought a new base gasket, right ? The new ones comes with an alum in middle sandwich much better than in previous old gasket. No need to place silicone as in old ones, just adjust outter engine crankcase bolts tight with proper tool.

Very important: Turn crankcase upside down, will see a gray water plug, seems that with salt water use internal plug wall begins to corrode, check for tiny bites or signs of surface corrosion, if so, polish lightly, place a thin layer of epoxy cement to cover complete plug. If plug begins to pee water will have a floded pan when engine is on not knowing where water comes from and driving you to near insanity while checking possible leaking spots.

Happy Boating

 

[Peter16]

Re: Tohatsu 18hp dies under load

i power tuned the pistons and the exhaust ports. ran a tap through all the threads to clean them up. The helicoil went smoothly thank god.

I installed a new thermostat when i serviced it 2 months ago. I removed it when i was using the oxy because i figured the gasket would burn and leak...

I am replacing the anode behind the exhaust plates.
The powerhead gasket is on back order for a while so i have to wit on that.

I dont know what plug grey water plug you are talking about.

 

[Sea Rider]

Re: Tohatsu 18hp dies under load

Check magneto plate linkage & rod factory parameters if ok, sorry the water plug is located opposite side of thermo at lower cylinder head, check if in good conditions, does not come as a spare. If with bits, time to repair before assemblig back crankcase to engine base.

Happy Boating

 

[Peter16]

Re: Tohatsu 18hp dies under load

finally all the parts arrived. Threw it back together friday night and took it for a run today.
I cant thank you all enough for accurately diagnosing the issue with this motor. I believe the leaking head gasket is what was doing it. The motor is running well now both in and out of the water.

thanks again

 

[Sea Rider]

Re: Tohatsu 18hp dies under load

Nice to read that finally your horse is runing well, most boaters don't take into account that you should torque to specs your head every 100 worked hours, by not doing so, you are letting the gasket which compresses and hardens with heat to experiment premature leaking failure due to salt water corrosion between water paths and gasket body which can let tiny water droplets pass into combustion chamber. Correct water flushing after use and gasket torque from time to time go hand in hand if wanting a long head gasket life with excellent engine performance.

If engine is not missing due to carb being clogged, it's the second largest mechanical failure cause you should look after, will give acceleration related problems specially at 3/4 throttle to wot speeds, if the leak is bigger, much worst including unexplained engine shutdowns.

Happy Boating