More power from tohatsu 30h

[busta420]

Are there any mods I can do to my 2012 tohatsu 30hp 2 stroke to gain a bit more power? I have just fitted a new S/S solace prop with slightly ported exh hub, I run 98 octane fuel and have advanced the timing 2 deg to suit, but am looking for any little bit I can squeeze out of it.
Cheers kenny

 

[pvanv]

Re: More power from tohatsu 30h

Are there any mods I can do to my 2012 tohatsu 30hp 2 stroke to gain a bit more power? I have just fitted a new S/S solace prop with slightly ported exh hub, I run 98 octane fuel and have advanced the timing 2 deg to suit, but am looking for any little bit I can squeeze out of it.
Cheers kenny

Kenny,

You didn't mention your exact model, which is critical. Year is unimportant for servicing a Tohatsu/Nissan outboard. I'm guessing you have an M30A3.

The [non-North American] 2-stroke M30A3 is at the top of the 25/30 hp family, so you already have all it can do, short of milling the head, porting, or installing aftermarket pistons. If you have stock head, block, and pistons, anything more than 89 octane is unnecessary -- and a waste of money, BTW, though it will still run just fine. Some premium fuels have better stabilization, and/or better detergents, so it isn't a complete waste -- just that the compression ratio of the motor does not need anything above 89 octane. For that matter, 87 runs OK as well. Aftermarket reeds, while well-advertised, don't idle as well, don't last as long, and tend to spit more, especially at lower RPM's.

The [North American] MFS30B is a 3-cylinder EFI, and the timing is not user-adjustable; The only way to up that motor's output would to reverse-engineer the ECU, which nobody in their right mind would do.

 

[Sea Rider]

Re: More power from tohatsu 30h

Welcome to the forums,

Some tech issues :

1-M30A3 is the top that will go.

2-That horse has a non adjustable carb throttle linkage that moves along timing plate, if you advance timing +2? will have excesive throttle cam over actuation gainst carb pawl. Place it back where used to be 25? with 180? buttefly opening at wot. No need to play with timing, was already factory set.

3-In order to play with diffrent props, pitches whatever you think might produce a better output, you need to go for a wot spin in flat no wind seas with you alone and check max rpm achieved at wot, that engine is rated at min 4,800, max 5500 rpm. Place a Tiny Tach 2A or Hardline's new model HR8061-2. Must adjust firing pattern to 180?, 2 spark per revolution.

4-If going with a induction tach check at wot which prop gives around 5,200/5,300 rpm and stay with it. Will have good hole shot & nice top speed. Buying props blindless is a waist of time, money and worst of all, could ruin your engine forever.

5-High octane fuels, some swear by them, others not. In my case runing 95 octane is much better, has better cleaning additives than 90, throttle response is much faster and engine runs smoother.

Happy Boating

 

[JB]

Re: More power from tohatsu 30h

There is some mixing of octane numbers. US 87 octane is rated at 91 octane elsewhere and US 89 octane is rated at 95 elsewhere.

It is important when stating octane numbers to specify where the fuel is sold.

 

[busta420]

Re: More power from tohatsu 30h 2 cylinder and made in Japan if that helps?

Re: More power from tohatsu 30h 2 cylinder and made in Japan if that helps?

It's an M30

 

[pvanv]

Re: More power from tohatsu 30h 2 cylinder and made in Japan if that helps?

Re: More power from tohatsu 30h 2 cylinder and made in Japan if that helps?

It's an M30

M30A3 or M30A4? Regardless... Your only options to increase hp on that 2-cyl 2-stroke are to go and see the machine shop for mods to the block, head, and pistons... and you could switch to aftermarket reeds. Probably not worth it financially, and you will end up with an off-warranty motor that does not idle as well, may have stumble, and will spit more through the carb at slower speeds.

Luis is correct... Dial-in the correct prop to achieve the factory-specified WOT RPM, and set the timing and throttle advance to factory specs for the best performance without very costly machine-shop mods.

 

[busta420]

Re: More power from tohatsu 30h 2 cylinder and made in Japan if that helps?

Re: More power from tohatsu 30h 2 cylinder and made in Japan if that helps?

M30A3 or M30A4? Regardless... Your only options to increase hp on that 2-cyl 2-stroke are to go and see the machine shop for mods to the block, head, and pistons... and you could switch to aftermarket reeds. Probably not worth it financially, and you will end up with an off-warranty motor that does not idle as well, may have stumble, and will spit more through the carb at slower speeds.

Luis is correct... Dial-in the correct prop to achieve the factory-specified WOT RPM, and set the timing and throttle advance to factory specs for the best performance without very costly machine-shop mods.

Hi guys thanks for the advice, much appreciated.
I have fitted a prop, but was given the wrong advice in pitch selection...only slightly. It is a 10"x13 pitch, which replaced the original 9.9x11".
The original was that quick out the hole that it was a bit silly, (almost throwing my fishing partner, a fairly big guy, off the front seat and over myself down back.)
But with the 13" pitch I have increased the speed from 42km/h to almost 50km/h, but has dramaticly slowed it down out the hole, which makes it a bit dangerous when in rougher conditions.
What type of compression is stock? and what type of increase would make it worth doing to benefit (98 octane is of consistant quality in Australia)
cheers kenny

 

[TOHATSU GURU]

Re: More power from tohatsu 30h

No benefit to a higher octane unless you screw with the timing and even then the the tiny, tiny increase would not normally be noticable. Compression will vary with the gauge so don't worry about the number itself. Just worry if there is a 10 psi difference between the cylinders.

 

[busta420]

Re: More power from tohatsu 30h

I'm taking it out this evening, while conditions are calm and i'm gonna have a fiddle with the tune with the assistance of GPS and an accelerometer that I use when tuning new performance accessories on my souped up road car.
These toys give accurate speed and g force info, I may be able to rob a bit of top end power and raise the low down torque with the right settings and carb jetting etc.
If I find any significant gains I'll let ya's know, thanks for the help guys kenny

 

[Sea Rider]

Re: More power from tohatsu 30h

The Tohatsu 30A3 is factory rated 4800-5500 rpm at wot and it's already set to 25? at factory, advancing + 2? to say 27? is useless because carb roller it's already at it's heighest peak at 25? with 180? carb butterfly, this type of block has a coil plate rod linkage that ends into a throttle cam which moves carb's pawl indirectly. Over actuation of all throttle parts is what you will achieve to gain nothing...

As you have already experimented can't have the best of both worlds in a single prop, that is, best hole shot with top end speed, it's one or the other. If it were my boat/engine would choose best hole shot with slight les top end speed.

Leave that horse as factory adjusted, place an induction tach and check which prop gives around 5300 rpm at wot, looking at your posted combo pic, a 30 HP is too poor to move that big boat as you intend to, that combo needs at least a 40. What does the tech plate specify under engine HP? Don't fiddle with props, tune without a tach, 2 strokes revs very high and fast....

Happy Boating

 

[busta420]

Re: More power from tohatsu 30h

the boat is rated at max of 40hp, but after having a fiddle with plug gapping, mixtures and timing along with trim adjustments im pretty happy with the overall setup, only wishing I got the 12" pitch, not 13 as it drops to a lower speed than the the 11" with a loaded boat (all fishing gear and a fairly big mate).
Also found the trim has great effect, but when set to optimum it occasionaly cavitates, and throug further inspection the anti ventilation plate is only 1/2'' below the bottom of the boat, and specs state 30mm min and 50mm optimum

 

[Sea Rider]

Re: More power from tohatsu 30h

AVP specs are just numbers from where to start, are not cast in stone. Trim should be adjusted for cav plate and well ballanced boat to ride paralell to water surface once under way at planing speed. Once this condition is met, check engine height at transom and fine tune height if needed. Once the sweet height spot is reached (flow passing slight under small upper deflector plate) engine will work much smoother and with punch.

Happy Boating