Yamaha 25/30 HP 2 Strokes Conversions

[Locozodiac]

Hi all

Does anybody knows what to change, alter in order to modify a Yahama 25 to 30 HP. Need to update an engine to use on a larger sib. Any ideas, thoughts, expertise are welcome.

Happy Boating

[tsnando]

Hello
It depends on what type of engine it is! If its a 2 cylinder them it's a 20/25 hp, If its an 3 cylinder than you have a 25/30 hp engine.

Try and find what the engine type is and i wil look in the yamaha manual i have at work, what parts they have in common.

i was thinking of doing the same on my 25hp but it's a 2cyl so im going to have to get some bigger carbs and do a bit o polyshing to get some more horsepower.

Cumps
Fernando

[Locozodiac]

Originally Posted by tsnando

Hello
It depends on what type of engine it is! If its a 2 cylinder them it's a 20/25 hp, If its an 3 cylinder than you have a 25/30 hp engine.

Try and find what the engine type is and i wil look in the yamaha manual i have at work, what parts they have in common.

i was thinking of doing the same on my 25hp but it's a 2cyl so im going to have to get some bigger carbs and do a bit o polyshing to get some more horsepower.

Cumps
Fernando

Hola Fernando

It's a Yam Enduro Model 25 HP, 2 St, 2 cylinder, 496 CC, 2007 engine. Seing a brochure, there are no 30 Enduros, the next one is a 40 HP. But there are 25/30 in the Sports range, both 2 cylinders, 496 CC too. The only difference between Enduro 25 and same Sport model are better chrome plated parts and 1 Kg more for the Enduro version. So, have a look to see what parts they share and which ones to change. Hope are easy to convert as Tohatsu's 25/30. Down here nobody sells/imports 20 HP engines, you say are same Yam 25/30 engines ?

Happy Boating

[Andy JC]

Originally Posted by tsnando

It depends on what type of engine it is! If its a 2 cylinder them it's a 20/25 hp, If its an 3 cylinder than you have a 25/30 hp engine.

Not necessarily true. I used to own a 30hp Yamaha twin, from memory I think it was a '98 model

[Polwart]

Originally Posted by Locozodiac

It's a Yam Enduro Model 25 HP, 2 St, 2 cylinder, 496 CC, 2007 engine. Seing a brochure, there are no 30 Enduros, the next one is a 40 HP. But there are 25/30 in the Sports range, both 2 cylinders, 496 CC too. The only difference between Enduro 25 and same Sport model are better chrome plated parts and 1 Kg more for the Enduro version. So, have a look to see what parts they share and which ones to change. Hope are easy to convert as Tohatsu's 25/30. Down here nobody sells/imports 20 HP engines, you say are same Yam 25/30 engines ?

Loc, Not sure if this will help you or not - I have a 2005 Yam 20D which is (as far as I can determine from the parts manual) is identical to the Yam 25N except for the carbs and exhaust. But this is a 2 cyl, 2str, with 395 cc; weighing 49kg. The next model up in the UK when I bought this would have been the 30D with 3 cyls and 496 cc weighing 59 kg.

[Locozodiac]

Originally Posted by Polwart

Loc, Not sure if this will help you or not - I have a 2005 Yam 20D which is (as far as I can determine from the parts manual) is identical to the Yam 25N except for the carbs and exhaust. But this is a 2 cyl, 2str, with 395 cc; weighing 49kg. The next model up in the UK when I bought this would have been the 30D with 3 cyls and 496 cc weighing 59 kg.

Thanks Pol, seems that there are many Yam versions for different countries, as don't use/sell Yam engines don't have the slightest idea betwen engine models. Will ask a local Yam tecnician who is well reputed , if cheap, will do the conversion with him, and definitely will be present to see how's done.

Happy Boating

[tsnando]

Hello
I Have a 25n and as far as i now it is similar to the 20d. At least it shears the same displacement and gearbox.


I will look tomorow at the two service manuals and try to cross reference the engines.
i am going to try and do some porting and exhaust work in the winter when the work slacks a bit, ill keep posting.
Just have to get my Sib back from the repair shop, to go catch some waves!

Cumps
Fernando