Tune up Tohatsu 25Hp

[Speedup]

Hi
Im planning to improve the out put of an Tohatsu 25Hp for racing purpose.

Anything to consider when adding a compressor to an four stroke engine?

[John.Vaught]

If it's a fourstroke it could be supercharged but it would be cheaper to buy a larger engine one that has power tilt and trim

[Speedup]

Hi John
I have been racing before and taken some more out put from engines.

Im planning to start racing in this new class. The engines which are in allowed to use is 20-25 hp.

Im know that an engines with higher scavenging air press need better pistons.

Engines is also a EFI type and im not familiar with that.

[John.Vaught]

Oh man you know I'm not sure with a tohatsu, I know Simon Motorsports can tune a Mercury computer.

In your racing class are superchargers allowed? 2 Strokes? Dry Stacks?

Tohatsu use to have a Mega 25hp motor that was a monster but I think it was a carb motor. Any four stroke will see a benefit from a higher compression ratio and as small as the motor is you could take it down and port and polish everything to reduce parasitic loss.

[John.Vaught]

Oh man you know I'm not sure with a tohatsu, I know Simon Motorsports can tune a Mercury computer.

In your racing class are superchargers allowed? 2 Strokes? Dry Stacks?

Tohatsu use to have a Mega 25hp motor that was a monster but I think it was a carb motor. Any four stroke will see a benefit from a higher compression ratio and as small as the motor is you could take it down and port and polish everything to reduce parasitic loss.

[Speedup]

Hi
Yes in this class we only have a limit from manufacture power out put which is 25hp. There is no limits with tuning up the engine, thats why its fun to try many ways...

Some people are racing with 2 stoke but i find it perhaps more easier to tune up a four stroke EFI engine if i will try to charge it.
2 stroke engine with this size is more complicated specially when carb. is installed.

Mainly Yamaha and Tohatsu engines are used in this class.

What do you mean dry stack?
Simon Motorsports. Any web size of this?

[John.Vaught]

http://www.simonmotorsports.com/

The lower unit and leg can be very restrictive so stacking skips the leg and lower unit by running the exhaust out of the cowling. Dry Stacking has no water in the exhaust to further reduce back pressure, it's really loud and with a two stroke it allows you attach expansion chambers so you can scavenge which dramatically helps a two stroke.

[Speedup]

Yes i know that the duct can be opened more but i go for 4 stroke engine.

I will take at the web site.

[John.Vaught]

Performance parts for that motor are going to be custom made more than likely.

But the owner of Simon may know of someone that can program your computer if he can't. I love these little motors they are how I started boating, I had a 15hp Yamaha that my dad and I modified and i would outrun a stock 25hp motor on the same boat.

[Speedup]

Yes i like small engine.
Budget is lower than big racing categories.

One Yamaha 70hp we took output to 130.

Programming is easy if you have the soft ware for the electronic unit.
I have experience of big CAT diesel engines but that and other story comparing to 4 stroke 25hp engine.

Do you have any good dealer of racing pistons, i guess exhaust temp will increase alot.?

[John.Vaught]

I'm sorry I don't know anymore it's been more than ten years since we messed with that little 15hp motor. I think we used wiseco pistons or I at least had a wiseco sticker.