Converting Mercury 9.9HP to 15HP

[OverNover]

G'day,

I have a 95-96 model Mercury 9.9HP pushing my little Edge Tracker along, hope to eventually upgrade to a 20HP however funds are tight at the moment, I've heard it mentioned that the 9.9's are exactly the same as a 15 but for a different carby or a spacer behind the carby which restricts it. Can anyone shed some light on this or know what needs to be changed to turn it into a 15HP, that extra 5 horses would be a big help, Cheers, Jamie.

[Mac_Attack]

OverNover
I have a 25hp Tohatsu which is a mirror image of a merc 30. I did the same to mine it helped alot ;D anyway just behind the carby is a small thin piece of metal. (i can post pictures if you want me to) Thats the restrictor thats what is stopping it from letting loose that extra power. You can do it yourself but best to take it to a marine tech as since your allowing more fuel into the engine you will need it to be rejetted to get that extra power. I didn't rejet mine and it was using more fuel not enough air and the mixture was running way rich. Hope this helped alittle.
Cheers Nick 8-)

[Blackened]

G'day

Mac Attack. Do you know if Jamie is talking about a jap or US merc??

Jamie, I have a US version 9.9 (shallow water drive, all gears/throttle on the tiller) and bottom line, it's not economically viable.

The difference is, 15 has a larger throated carby, not just jets. 15 has different sized ports and the timing is a dew degrese advanced.

Search for a thread, probably 10mths ago, I went into this in depth, talked to a dozen or so mechanics and had 3 of them thoroughly check the schematics for part numbers.

At the end of the day, It's not worth it.

For now, make sure your engine is set up right (height and prop) and live with it

Dave

[Noelm]

fully agree, this pops up all the time, and indeed there is a very small number of Motors that can be upgraded, but they are very few and far between, a lot of Motors share a SIMILAR block and crank, and have the same capacity, and a lot also seem the same untill you either look at an OEM parts list, or know a bit about them, usually all you end up with is a poor performing pile of crap, that would have been better left alone! the biggest dud of all is the old 90 to 115 OMC conversion, now that one causes some real headaches!

[OverNover]

Thanx guys, think I'll leave the old girl alone and save the $$$ for a proper upgrade, Cheers for your input.

[Blackened]

Thanx guys, think I'll leave the old girl alone and save the $$$ for a proper upgrade, Cheers for your input.

G'day

Good move;)

Dave