Yamaha 40hp 4 stroke

[Jomaweb]

i purchased my boat and went for the yamaha 40 4/stroke. i adore the motor, i have it on a 4.2m Quintrex Dory. I get about 45km/h full throttle, which is ok not over fussed about it though, is there anyway of doing any small mods to the motor to boost the performance any ? I herd from some people that carbies can be changed on certain motors to give better preformance, thanks.

[Dan5]

Mate do not play with the carby's...........You are far better off playing around with prop's and engine height........mucking around with carby's is asking for trouble they are fine the way they are.....find out what prop you have on now the work from there,it's proberbly a 11 1/4 x 12.....try a 11 3/8 x 13 for a bit more top speed.

Cheers Dan....

[Jomaweb]

thanks for your reply, it just has the prop they gave me, it is a 11 3/8 x 12 G ?? will the 13 make a difference ? will a set of stingrays help ? or is that just planeing speed ?

[Noelm]

a bit late to reply to this, but before you swap props, make sure your enging can reach full Max RPM's, if it does not, then a bigger prop will not give you any more speed, but it will slowly kill your engine

[Jomaweb]

no not too late, how do i know what rpm it will reach, i dont have any guages, only tillerstear ??