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mercury 9.9 conversion to 15 hp

What year is your motor? The 9.9 was built on 2 different blocks the 10 cid block cannot be converted. If you can make the conversion I believe you also need the exhaust tuner.
 
I converted a couple 2 stroke 9.9's to 15's (had to be the 95 or later with the larger displacement).

In "on water tests with gps", the same boat, same gear, same guys etc, we saw "no more than" a 2 mph change in top speed. The hole shot and time to plane is pretty much identical, it's only the very top end that changes "minimally".

Anyone that say "I can notice the difference" is probably lying to justify the cost outlay for the conversion to themselves.

You need a lot more horsepower to get even a mediocre speed increase.
 
galamb said:
I converted a couple 2 stroke 9.9's to 15's (had to be the 95 or later with the larger displacement).

In "on water tests with gps", the same boat, same gear, same guys etc, we saw "no more than" a 2 mph change in top speed. The hole shot and time to plane is pretty much identical, it's only the very top end that changes "minimally".

Anyone that say "I can notice the difference" is probably lying to justify the cost outlay for the conversion to themselves.

You need a lot more horsepower to get even a mediocre speed increase.
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Hello! I was reading through some old threads and came across this. I recently picked up a 1993 Mariner 9.9 which i was told had a 15hp carb on it. It seems to run good. But ive read the block itself that year was different. Do you know if this is accurate? if so is there any benefit to leaving the 15 carb on? or any harm? Thank you!

-Brandon
 
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