Tohatsu 25hp to 30hp ?

[Commando C2]

hi
i have just bought a 2000 model tohatsu 25hp and have seen on this and other forums that its possible to uprate them to 30hp.

i followed some threads but the final results after fettling with gaskets and timing werent posted.

I had a look down the venturi tube and cant see the small gasket with small slit in it that the 25hp has.
perhaps its already been changed, but the timing is still on 20degrees.

how important is the timing change and what difference will having the engine at 25 or 20 degrees make?

will remove carb soon to check the gasket situation but any advice from people who have successfully completed this mod would be good.

its a 2 stroke by the way.


thanks

 

[TOHATSU GURU]

Re: Tohatsu 25hp to 30hp ?

The slit means it has the 25 hp gasket. Depending on the exact model 25 it may need to have the timing changed or may not. It depends on which Jap tech did the run out.

 

[dimerz]

Re: Tohatsu 25hp to 30hp ?

Correct me if I'm wrong but isn't there also a pilot screw adjustment?

 

[TOHATSU GURU]

Re: Tohatsu 25hp to 30hp ?

No, there is not.

 

[Sea Rider]

Re: Tohatsu 25hp to 30hp ?

If your engine is same as this one, check procedures. Change carb gasket accordingly, if you have 20? deg will need to lose stopper bolt A, turn screw CCW to add more ? , while playing with screw CCW, full throttle until mark reaches 25? deg and throttle cam pushes butterfly completely flat, adjust nut tight. Do not play with rod's factory height adjustments 3 & 4. Probably will need a slight mixture screw adjustment as carb will breath more air than before. Now will have 30 HP at throttle's end with better hole shot, more weight to carry and more gas consumption at full wot, so 3/4 will be the way to go if gas is an issue for you.

Happy Boating

 

[Commando C2]

Re: Tohatsu 25hp to 30hp ?

thanks for the info guys

i loosened the carb today and the gasket in there is the 30hp fully open gasket.

The butterfly is alos fully open with the throttle at max.

The timing marks seem to be at 20 degrees, although i am not sure at where it is measured. i looks like the same as those attached thumbnails and the pic of the timing marks.

i havent tried it on my boat yet though to see if it feels more powerful than my 25hp evinrude.

also where is the mixture screw on this carb?
i have lowered the idle a bit with the throttle stop on the left of the carb with the small spring under it.
When i put it in reverse she makes a bit of a clunk that doesnt sound too comfortable but is less when the idle is slower? any ideas of this? adjustment somewhere?


cheers

 

[Commando C2]

Re: Tohatsu 25hp to 30hp ?

heres a pic of the timing marks on my engine and the position they are in.

 

[Commando C2]

Re: Tohatsu 25hp to 30hp ?

Hi Searider

Just to clarify...what does CCW mean? i can only guess "counter clockwise"?

If the butterfly valve is fully open and the throttle stop is letting the throttle open as much as possible does this mean the ignition is 25degrees?

I cant really see what lines or marks are supposed to line up with each other, from the pic, for example the case matting surface?

I am hoping that she has been uprated fully already.
the engine was bought on the gold coast of OZ and has a sticker on the side saying something about meeting canadian regulations?!!!

 

[Sea Rider]

Re: Tohatsu 25hp to 30hp ?

heres a pic of the timing marks on my engine and the position they are in.

The second position, 25? with 180? butterfly angle is the correct at full throttle. Your comments are right, CCW counterclockwise, the timming mark is the matting surfaces, a black line of about 2 mm thick. If all issues are like stated on previous pics, you have a already converted 30 HP engine, but didn't know.

Happy Boating

 

[Commando C2]

Re: Tohatsu 25hp to 30hp ?

thanks for the help
i can see the 2mm thick part of the casing now after looking at my picture closer.
Seems like someone else has already done the job for me.
great. cant wait to try it out.

I just need to try and sort the rather clunky noise going into reverse.
Are these tohatsu's a bit like that or is there something that needs adjustment?

perhaps i need to start a new thread?....

 

[Sea Rider]

Re: Tohatsu 25hp to 30hp ?

thanks for the help
i can see the 2mm thick part of the casing now after looking at my picture closer.
Seems like someone else has already done the job for me.
great. cant wait to try it out.

I just need to try and sort the rather clunky noise going into reverse.
Are these tohatsu's a bit like that or is there something that needs adjustment?

perhaps i need to start a new thread?....

With engine off, place gear to forward, move throttle to 1/2 and full throttle again to end stop, see if the carb butterfly has reached flat 180? if not may need a slight readjustment of the A stopper screw CCW. The only difference with respect to 25 HP is that will have better hole shot with heavier sib/rib, once on plane reduce to 3/4 thottle for better gas consumption. You can turn stopper B fully CW until stops to lessen the extreme right slack movement of the throttle grip at minimum/idle position. Put a thick oil drop in every sliding throttle /carb part including white nylon bushings so to have minimum wear.

With respect to the reversing noise, is it a one time loud clak or it' s a continuous claking ? if it's the first, slow rpm a bit (at idle, turn vertical screw ccw at carb pawl until rpm's begin to lower) check that engines doesn't turn off when gearing. Lowering rpm will lower clak noise a bit. Find normal in these 25/30 engines to clak a bit louder in reverse than in forward, change tail oil for new( sae 80/90) as you would not know previous owner last time change.

Happy Boating

 

[Commando C2]

Re: Tohatsu 25hp to 30hp ?

Thanks Searider

The butterfly is fully open at WOT. the hull of my boat limits the max speed as its not a rigid hull but a hard skin type with a fold out wooden keel. the extra power low down will make it more useable and useful to me.


The noise going into reverse is just a one time noise when it goes into reverser, once its in its fine. I have turned down the idle a bit to lessen the noise. the last owner says he had the oil changed 6 months ago and has only used it a few times trawling in a lake.
might check the level of it or change it anyway.

does heavier weight oil help?
good to know that these engines make a bit of a noise going into reverse.
My evinrudes that i have a super smooth going into gears so are the only comparison i have really.


thanks again

 

[Sea Rider]

Re: Tohatsu 25hp to 30hp ?

Hola Commando 2

So you have a black Commando Zodiac, right. The only way to achieve better top end speed and handling is to inflate that sib to it's full recommended air pressure (3.5 psi) so to have a more balanced rigid sib. Other issues that lowers final top end speed are water splashing against back transom as flowing water level in not passing under cav plate at a 90? boat/engine angle, but rather splashing against square tail exhaust on upper cav plate. This problem occurs with sibs not having a minimum of 40 cm transom height.

SAE 90 or multigrade 80/90 is recommended for outboards engines, same as in you car gearbox, no need to use a thicker one, change every 100 worked hours.

 

[Commando C2]

Re: Tohatsu 25hp to 30hp ?

thank for the info.
once more i shall request the knowledge of interested parties......

I got the engine out today and it leaked some watery/oily gunge from the prop /skeg area
it was also making more of a noise going into reverse and forward than it seemed last time.
It sounds very metal against metal so i am thinking that there is a gearbox oil leak.
I took off the prop and the spline nut was not very tight at all, the prop could move about 3-4 mm.
Also the seal around where the spline shaft goes into the gearbox housing was rusty and corroded but didnt seem to be leaking when inspecting it ( i had just run it so it had been wet)

Can someone direct me to a site to get the exact part no for these seals and also the seal on the oil filler screws as these seem to be constantly oily

I suspect the oil level is low hence the clanking into gear noise.

i think i need to start a new thread now dont i?

PS yes i do have a bombard commando C2 3.5m.