30hp Yamaha mods?

[Notcho]

New to the forum and tried the search but couldn't get the answers I was looking for.

I have a 1989 Yamaha 30hp that I want to get some more reliable power out of it. The motor is used for fishing and hunting but I want squeak out some hidden power if possible, nothing extreme just some basics. First thought is to mill the head but how much do I need to take off for running non-oxy premium? Also I see a aftermarket exhaust tuner is available. Are those worth it? I have some performance reeds already and the powerhead is solid. Any real experience with these motors is appreciated.

[Jason Johnson]

Safe little wake up, cut .030 off the head and install 40 tohatsu carbs, yammi 40 reed cages and CCM reeds. Do not touch the exhaust.

[Notcho]

Thanks for the info, already have the CCM reeds. What kind of compression would .030 give me and are the 40 Tohatsu carbs a bolt on?

[smith625]

The carbs with the cages Jason mentioned are a bolt on, he would know the psi gain from milling.

[Jason Johnson]

If you cut .040 the pistons will ever so lightly touch, that will give you 150psi. then you remove the head again and lightly sand the pistons. the word UP will transfer from pistons to head. .030 should be 135 - 145. The tohasu carbs are a little work, not bad though, got to restack them, mid to bottom bottom to mid. You need to cut open the carb plate, blend the holes. Also a little work for the vacume to the fuel pump. But a afternoon job at most. Don't forget the 40hp yammi reed blocks.

[Notcho]

Where do I find the Tohatsu carbs? What years work? I did a google search but couldn't find any info.

[Xpress2830]

I had a stock 25 3-cylinder on an Xpress 1546VJ jack plate stock motor just me ran 28MPH with a Power Tech SRA3 11 pitch turnin 5600RPM. Added 40/50 stock reed cages, 40 carbs opened intake to match carb venturi, shortened 30 tuner cut off just at water intake. Boat ran 43MPH at 6400 RPM Turbo hot Shot 13 pitch. This was just me 185lbs and 6 gallons of fuel. Hope this helps..

[tunnelmike]

I've got a clean set of pro v 50 Yamaha carbs if you can use them. Jason knows ! He was flying after fixing the flooding problem. Good show ! Mike

[Rohdy]

What is the reasoning for not touching the exhaust? Sorry just curious and I'm trying to figure out best set-up on my yami 30 mshr.

[nitro_rat]

What is the reasoning for not touching the exhaust? Sorry just curious and I'm trying to figure out best set-up on my yami 30 mshr.

Probably would kill the bottom end, just a guess. I have no experience with these specifically.