12" mid with exhaust dump.
Tohatsu M40C Racing
My personal blog for development of the M40C tohatsu outboard motor for racing and recreational purp
10/05/2026
Woohoo ! Finally seeing the fruits of this Hybrid engine / twin carb build.
Been smelling like 2 stroke, smoking myself out trying to get the carbs tuned and set up correctly with timing.
Sorry no video yet, BUT a quick test run yesterday finally proved successful.
Started easy, idled perfectly in gear cold, and then ripped through low, mid to high speed jetting without hesitation, stalling, bogging or spluttering ! Top end started pulling like a scalded cat! With no indication yet of plateauing out up top. It just kept creeping up speed top end and revs were estimated at approx 7k plus rpm ! Plug chops and re jetting for fine tune stoich now, I set it a little rich to begin with for obvious reasons.
Now to start leaning it out on the mains, check butterfly's are opening fully as timing was set conservatively at approx 22° WOT. So there's alot more in it yet, before I just couldn't get past the set up for low/mid/ top transition.
Few extra bolt on performance mods up my sleeve to go yet, one thats going to increase performance drastically when completed.
So far this venture is proving to be able to turn the 40c into a 50hp+ weapon! Stay tuned for next test run, ill get some numbers and videos to share. Thanks for following me on this venture of the 550cc APBA Super Sports Class, fishing motor race engine😜
05/05/2026
Playing with AI, its helpful at times to bring your ideas quickly into vision.
Was thinking to rename my boat, as it will be 'born again' soon, with my newly devoloped hybrid outboard motor set up ( approx 55hp ) coming back to the race scene, "Exodus" just carries such a bold, dramatic weight—like it's breaking free, racing toward a new horizon. It’s got this powerful, spiritual vibe, like it's leaving the old world behind and blazing a fresh path.
So every time i launch this boat, it’s not just speed—it’s a statement.
“Exodus” really does feel like more than a name…more than the previous name more like self ego, ( Alter Ego ) ( was named after my Dads 1st ski boat 'Ego' ). I think it’s got that sense of departure with intent. Not just leaving the ramp, but escaping gravity itself because when that hull lifts and the prop starts singing, exhaust screaming screaming, it’s going to be like the boat’s answering its own name.
It also has that clean, punchy look on the side of a race hull that can be better seen at high speeds, because this boat is going to be Flying !
What's everyone thoughts ?
Sounds pretty toey for a tohay🤪
Needs timing tuned. Can tell by the sound of it.
Its alive again , again ! Went to rebuild it, thinking i had cooked it as the LWP adapter to the garden hose came off , ran dry, got hot, sizzling the head, then locked up trying to restart after cooling a bit, turned out a magnet I had glued in came loose from the excess heat and jammed up under the flywheel. The bores and pistons were fine! Reassembled, new water pump kit ( destroyed it running dry no water ). Now to continue tuning it, looks like ive destroyed a starter motor from misalignment now also. Getting there i guess.... I know 1 thing, I need a start switch at the engine, trying to reach the dash and operate the throttle at the same time is like a circus act waiting to go wrong. Engine sounds lumpy for a twin carb set up now, and is liking more advance than std.. need a timing marker next to dial it all in. I can see a reshape of the throttle cam is in order too. Will need more advance earlier.
27/11/2025
Next investment. Best part Australian made !
25/11/2025
Keep on rolling on with the project, ( Ai pic for fun )
Dropped the block off for some +1.00 oversize pistons. Ordered new top and bottom crankshaft bearings and seals, gaskets & o rings and a new water pump housing kit. (Expecting it to be melted).
Lesson learnt, strap the bloody hose on the LWP , or run it in a bucket, NO exceptions.
After the flywheel biting me twice, disintegrated a top crankshaft bearing , now cooked an engine with no cooling, surely its going to all be good to go next build as i think this Frankenstein motor didn't like being brought to life and has been fighting me the whole time.
Progress Tuning so far :-
Pilot - 92
Needle and seat 110
Main jet - drilled 1.5mm ( 150)
Airspeed @ 1 turn out.
Timing advance locked off @ 25°BTDC.
Things to do :- Advanced timing to 30° with stator modifications.
Fit timing marker and pointer.
Play with airspeed jets for peak idle tune.
Gearbox rebuild.
Full crankshaft rebuild and balance.
Slight porting and clean up for increased flow, with revised exhaust height for peak power at higher RPM.
Paint engine and boat.
24/11/2025
The good news and the bad news :-
Bad news, I managed to start jetting the carbs finding a good base to begin with, it was all going to plan, until the hose came off the leg on the driveway testing it, and cooked the motor real good. Complete rebuild now on the cards, new crank, bore, pistons, water pump, gaskets... bugga, just when I had it ready to water test again, with near correct jetting / tune, I cook it.
Its telling me, its not ready yet.
Good news, picture is A.I. generated😝
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