Mercury 9.9 to 15 hp

[roadking]

my 9.9 started to give me problems this weekend it seemed to be starving for fuel i cleaned the filter and took off the carb to make sure no dirt or contaminates were in needle valve on in bowl i also changed the fuel in the tank just be be sure there wasnt water in the fuel. It ran fine until i gave it alot of gas it seems to be starving for fuel? I also called mercury marine and was told that the engines were exactly alike except for the carb.(but they couldnt tell me it was ok to change carb because of epa standards)After reading some of the post here it seems there are different opinions about that .Has anyone changed the carb with success?

 

[The Marine Doctor]

Re: Mercury 9.9 to 15 hp

I will take a stab at this.<br /><br />Not with a 9.9-15 conversion but with a 30-40hp conversion.<br /><br />1997 2 cyl 30 = 40hp.<br /><br />What you have to do. Change the high speed jetting to that of a 40hp. Take the reed stops off the reed blocks.<br /><br />Generally speaking. When you want increased performance from the same size block. You must increase the amount of AIR/FUEL that is available to the engine. After doing this...provided the exhaust is large enough and tuned properly...you will have a higher HP engine.<br /><br /> I bet you all thought there was more to it!<br /><br />Now Please do not email me asking for info on all engines to do this. Its risky and if not done properly...will destroy your engine.<br /><br />TMD

 

[FlyBoyMark]

Re: Mercury 9.9 to 15 hp

Late model 3 cylinder 2 cycle Mercury 40 to 50 Hp requires new oil pump and three new carbs that are bigger plus removal of reed stops and addition of reed retainer washer.('bout $400.00 discounted, old parts are worth somthn' I guess..You can save 100 bucks by skipping using oil pump and use premix) 60 Hp is same block again except for some port work and bigger carbs again, same induction setup as 40 and 50 Hp, uses same oil pump as 50 HP) Mercury 20 hp to 25 hp is carb only...

 

[Skinsk]

Re: Mercury 9.9 to 15 hp

The 9.9 is simply a de-tuned 15hp motor. I've seen people convert the 9.9, just be swapping carbs, and it works. Of course I've also seen people buy 9.9 decals and put them on their 15hp . <br />The carb switch is really pretty much that simple. <br /><br />Scott.