Tohatsu m18c need carb kit and fuel pump kit.

[martinmatt88]

My tohatsu m18c has a miss will under a load and a slight miss at top end. I have ran seafoam and have soaked the carb in hot carb dip but still doesn't run to full potential. Any ideas on where I could get a carb rebuild kit and or a fuel pump kit? Thank you.

 

[Sea Rider]

Welcome to Iboats,

Described miss happens while OB is cold say on first morning start, what about when fully warmed up ? does OB still miss ? If it's a temp issue, changing carb parts and fuel pump kits won?t cure that symptom. Is thermo in good working order, it's clean, not rusted, salted ?

Happy Boating

 

[martinmatt88]

The miss is consistent when the motor is cold or has been ran for an hour. The temp is good, constant flow of water coming out of return hole. Water coming out return hole is a normal temp. (Not hot to the touch). I pumped the bulb while missing heavy at accelerating throttle to see if it would pick up. Still the same lugging miss. Was checking to see if I was loosing prime slightly. Bulb seemed to be remaining primed.

 

[martinmatt88]

And thank you. I have used the heck out of this boating forum for years. Old threads has helped me alot with working on boat motors. Thanks for yalls help. greatly appriciated.

 

[Sea Rider]

How old is that OB ? has low or high hour use ? The miss is something as if OB doesn't want to accelerate, hesitates when passing from idle to a faster speed or it's a bog down issue ? same bog down issue at near full throttle ?

Happy Boating

 

[martinmatt88]

I believe it is an 86-90 model. I'm sure it has quite a bit of hours on it. This motor will idle all day long and never die. When I throttle from idle it will have a miss under load and when I am plained out at full throttle there is still a slight miss. When I back off to 3/4 throttle it doesn't seem to miss as bad. Very noticeable though when I punch it from idle and it is trying to plain out. I have this motor on a riveted 15/36 aluminum duracraft. It should stand that light boat and be gone when I floor the throttle.

 

[Sea Rider]

Personally before investing on a carb & fuel pump kit, would invest on a cylinder head gasket along a thermostat if in bad shape. Gaskets don't last that long if cylinder head has not been re torqued sometime after break in period ended and from time to time.



Gasket cedes, compresses, and combustion chamber does not seal perfect. Water gets in and OB starts missing, worst at 3/4 to full hammer down. Is that 18 been used on fresh or salt water ?

Happy Boating

 

[martinmatt88]

It's been only on fresh water.

 

[Sea Rider]

Some issues :

Assume OB is sufficiently warmed up, say min 2 minutes.
-When the miss occurs is like OB "doesn't want to accelerate, hesitates" for some seconds.
-How about when passing from idle to half throttle, will this miss fully disappear if letting OB run at that throttle setting for some seconds ?
-We're not talking about OB bogging down, just missing, hesitation issues, right ?

Happy Boating

 

[martinmatt88]

Steady throttle at 3/4 throttle is the only time the motor seems to run smoothly without a miss. It does hesitate during acceleration. It does seem to do better at steady throttle accept when at steady full throttle.

 

[Sea Rider]

If there's paint peeling off right in middle of both mating surfaces, where cylinder gaskets lives, that's an indication that gasket is not sealing as it should, it's already compressed, hardened, dried, kaput. Running an OB with gasket issues in fresh or salt water gives same symptoms.

If you plan staying with that simple OB and having fun with it, remove powerhead, remove thermo, clean all water paths, clean/sand both powerhead's mating surfaces to smooth cond. Take advantage to decarbon internal head and piston head as well. Torque head gasket to 28 NM with a trorque wrench or take powerhead to a mechanic shop that can retorque it for you.

Will need the following spare parts : head, lower, thermo gaskets, plug set & thermo. That nice 18 is worth a complete powerhead restoration..

Happy Boating

 

[martinmatt88]

I know you aren't supposed to run motor out of water but I start it and rev it up in neutral and it still has that miss. I did this to see if it still had the miss with no water. Would it still be the head gasket?

 

[Sea Rider]

Could be a head gasket issue provided that fuel pump, carb, all electricals are in 100% working order. Didn't tell if white lines are seen where indicated ?

Happy Boating

 

[martinmatt88]

What do you mean by white lines?

 

[Sea Rider]

Check..are lines around head gasket and crankcase, or paint has peeled off from that area..



Do you have them ?

Happy Boating