9.5 hp modifications

[Old outboard dude]

Carb upgrade?

Would their be any problems with putting like a 15 hp carb similar to my 1979 6 hp evinrudes carb other than throttle linkage, choke linkage and connecting the carb to the motor? Ps I would have to make a specific connector peice for the carb to connect to the motor. This might sound like a crazy idea but I just want to know if it's possible and what the outcome would be.

 

[flyingscott]

I doubt if it would run right. By the time you got done buying the carb which is not cheap and getting it to work you could buy a 15 hp

 

[Old outboard dude]

I have a 68 9.5 hp evinrude that I would like to modify for more hp just for fun. I will consider pretty much anything, is it possible to modify the exaust? Carb?( I can get about a quarter more turn on the throttle) SUGGUST ANYTHING THAT MAY BE POSSIBLE without completely destroying the motor.

 

[Old outboard dude]

I'm not looking to get my money's worth just would like to do it for fun

 

[racerone]

Make it worth while and fit a 35 hp carburetor on to you 6 hp.

 

[ondarvr]

Of all the motors to try and modify, that might one the least likely candidates for success.

 

[F_R]

Man, you are heading into unknown territory. I totally respect your "just for fun" attitude, and that is what it will be. But as someone mentioned, that is a pretty unlikely candidate, being as everything on it is so complex. Enjoy yourself and "have fun".

 

[Scott Danforth]

fastest way to convert an outboard to more HP

sell outboard and convert to small pile of cash
open wallet, add contents to pile of cash
take pile of cash, buy bigger outboard

while there is a bit of power that can be obtained in certain outboard power heads where the 10hp shared the same block casting as the 15hp, its much easier to find a complete 15hp power head and swap as by the time you swap over all the parts, you have spent double the amount of money and time vs buying a 15hp.

 

[Chinewalker]

9.5hp - No way to modify easily. Not practical to modify even if you're a machinist.

6hp with 15hp carb. Will run like crap, if it runs at all. Simply not enough compression volume in the crankcase to draw enough fuel through the larger carb.

 

[F_R]

Everybody thinks a bigger carburetor will make their boat go faster. If that were true, you could put a 40hp carb on a 4hp and go screaming across the lake. Sorry folks, it just doesn't work that way. Carburetors must be matched to the CFM (Cubic Feet per Minute) of air going through them. But true you can put on a Smaller carburetor and reduce the horsepower, as is the case with the 9.9/15hp series.

 

[gm280]

There are only a few ways to extract that extra bit of power from any engine. Boring it out to max, is one way. And allowing the exhaust to free flow helps as well. You could even put a tuned port exhaust on it and turn the length for optimal top end speed. However, when you go for the max, you know the idle will suffer without a doubt.

I do remember flying R/C back in the days, and the most favorite way to extract more power from an engine was a tuned exhaust. They called them tuned pipes. Amazing what you could do with that type setup. But there were other timing issues that were used as well. Schnuerle Porting was a big thing as well. It changed the port timing so that scavenging helped flow fuel through the engine easier. So there are ways, but as you stated, it is an iffy science and you have to know your engine is a guinea pig as you try for more power.

But you also need to understand that with that extra power comes higher RPMs and that poses an additional load on the crank and bearing. You could even go to a forced fuel system to move more fuel in for a better charge. But then you need more air. Nitro comes into the picture or even a blower. But it can be done... JMHO