20hp to 25hp ???

[breamking]

I have a 2000 model mariner 20hp long shaft and would like to make it 25hp.Apart from a prop change would this be possible and how.Thanks.

[Blackened]

G'day
From what I read you would like to make the engine produce 25hp, instead of the current 20?. A prop change WILL NOT increase horsepower in an engine.

If all the specs are the same then more than likely it will be a carby adjustment such as jets or restrictor plate.

What Yesr model is the mariner? Best thing to do is call the mechanic. Failing that, kopey or BM may have a better idea.


Dave

[breamking]

Thanks blackened. It is a 2000 model.I new that the prop would not make it 25hp but if I could turn the motor into a 25hp then I would be able to put the 25hp prop on it.Any help appreciated.

[kneebone]

I have a 25hp merc and it has been upgraded to a 30hp by taking out a restrictor on the carb intake and retuned by cunninghams. Dont know if it can be done to a marina

[Noelm]

there is a whole lot more to making one outboard to another higher HP than just "taking out a restrictor" sure they may share the same basic piston, crank etc, but there is usually a whole host of differences,in cluding ports and heads,and carby jetting/manifolding, been there and done that with heaps of makes and models over the years.

[joey_1987]

The 20hp Mariner in question can be upgraded to a 25hp, it won't be as simple as a restrictor plate though, I remember reading that to turn that 20hp engine into a 25hp then you need to change the carby and to buy the bigger carby is too expensive to make it worthwhile, better off sourcing a second hand one. Unsure of what else needs to be changed, perhaps the carby jets also? Kneebone's motor is actually a Tohatsu built 25/30hp, all that seperates these two models is a restrictor plate which can be removed cheaply and easily. Cheers.