Tohatsu 25hp improvments

[FSLSC]

gday guys from australia, quick intro, im a member of a surf life saving club and one of the sports we participte in is IRB racing (inflatable rescue boats) they are a 3.75m Achilles inflatable boat and we race with 25hp tohatsu's

for racing only minor tuning mods etc are allowed and i was just curious how i could tune out motors so they have a quick acceleration with out comprimising the top speed, im pretty certian the timing has been altered and the spark plug gap has been decreased yet id just like a quick overview on what this does and what i can do to improve this

cheers guys
Cameron

 

[pvanv]

Re: Tohatsu 25hp improvments

Are these the new EFI 3-cylinder motors, or the older 2-stroke carbureted units? Do you have a model number we can go by?

 

[FSLSC]

Re: Tohatsu 25hp improvments

they are the 2 cylinder carbie models, with the newest one being 6 months old. i dont have a part # atm, but they are the black with red writing on the cowling cover

 

[pvanv]

Re: Tohatsu 25hp improvments

TG will be the expert on these. They are pretty basic 2-strokers, NLA in the US, and the usual 2-stroke mods will apply.

 

[FSLSC]

Re: Tohatsu 25hp improvments

excellent, cheers mate, we can sit on 43kmh+ but we still need more speed hahaha

 

[Shubobo72315]

Re: Tohatsu 25hp improvments

what are some of these 2 stroke mods? I always want my boat to go a little quicker.

 

[pvanv]

Re: Tohatsu 25hp improvments

One mod that comes to mind is removing the induction restrictor (if present), and re-synchronizing the ignition. On some models, that gave you about 5 more hp.

The forum expert on the Tohatsu 2-strokes is TG. Maybe he has some specifics for your motor.

 

[TOHATSU GURU]

Re: Tohatsu 25hp improvments

Change the carburetor manifold gasket to the one that comes on the 30 and advance the timing by two degrees.

 

[FSLSC]

Re: Tohatsu 25hp improvments

cheers TG but i should have stated the removal of the restrictor plate is not allowed, however ill look into the timing

cheers for that and appologies for a slow reply

 

[deejaycee_2000]

Re: Tohatsu 25hp improvments

There are quite a few mods you can do, so you need to tell us what you are not alloud to do .....

 

[cwhite6]

Re: Tohatsu 25hp improvments

Where would I get the correct manifold gaskets for the 30hp motor? Also, how do I advance the timing? I have a Nissan NS25C. It is a '94. Is this all that is required to make it a 30HP? I noted they are the same engine.

 

[pvanv]

Re: Tohatsu 25hp improvments

You can get the parts from any Tohatsu or Nissan dealer. You will find timing information in the service manual, also available from a dealer.

 

[cwhite6]

Re: Tohatsu 25hp improvments

I posted this elsewhere, but no responses so far. I keep seeing conflicting information. Do I need to change just the gasket, gasket and timing, or gasket, timing and block in the tiller? Thanks.

 

[pvanv]

Re: Tohatsu 25hp improvments

Change the carburetor manifold gasket to the one that comes on the 30 and advance the timing by two degrees.

That's all.

 

[cwhite6]

Re: Tohatsu 25hp improvments

Thanks alot. Now I just need to find a service manual for it.

 

[pvanv]

Re: Tohatsu 25hp improvments

Thanks alot. Now I just need to find a service manual for it.

Get a Factory manual from a dealer, not an aftermarket doorstop.

 

[cwhite6]

Re: Tohatsu 25hp improvments

I was planning on it. Having owned and worked on Harleys using the factory service manual, I pretty familiar with the value of them.

 

[TOHATSU GURU]

Re: Tohatsu 25hp improvments

If you have a tiller model you will need to pry the block out the grip so that the throttle will open all the way....That's if the glued in block is still in place.

 

[cwhite6]

Re: Tohatsu 25hp improvments

I took the handle off of the tiller. There is no block in there. Now, I need to figure out to fix the horrid hunk of metal I found attached to the tiller under the cowling.

 

[FSLSC]

Re: Tohatsu 25hp improvments

There are quite a few mods you can do, so you need to tell us what you are not alloud to do .....

sorry for slow reply, the motor has to remain "sealed" ie no internal modifications, nor can we remove the restrictor plate, basicaly mainly timing and ignition mods