9.9

[VINTAGEVECTOR225]

does anybody know the diff between 9.9 and a 15hp evenrude,can you cut the head?and how much? bump up the timing?and how much?releive the exaust?i am rebulding for a guy for his inflateabel and he wants more power,i have ordered boyseen reeds for it and was wondering what else i could do to it.i am not familer whith this moter,thanks

[jtb]

does anybody know the diff between 9.9 and a 15hp evenrude,can you cut the head?and how much? bump up the timing?and how much?releive the exaust?i am rebulding for a guy for his inflateabel and he wants more power,i have ordered boyseen reeds for it and was wondering what else i could do to it.i am not familer whith this moter,thanks

change the carb to a 15. that to me would be the biggest diff.

[jtb]

Thinking about it I may have a new style 15 carb (plastic top) @ my house. I'll look tonight if you are interested.

[VINTAGEVECTOR225]

Thinking about it I may have a new style 15 carb (plastic top) @ my house. I'll look tonight if you are interested.

thanks

[Skoontz]

I believe are the only two significant differences. that plastic topped carb won't flow like the all metal versions, but it will get the basic job done.

[jtb]

I believe are the only two significant differences. that plastic topped carb won't flow like the all metal versions, but it will get the basic job done.
can't get my metal one, it's no the J-hydro!:)

[Skoontz]

Metal carbs available, Sea Way Marine, $175.00 each

[jeff55vDSH]

does anybody know the diff between 9.9 and a 15hp evenrude

I dunno how to change from a 9.9 to 15.
BUT-
I do know how to change a motor from a 15 to a 9.9...change the engine cover.
:rolleyes:
At least, that seems to be how everyone around here does it.
:rolleyes:

[VINTAGEVECTOR225]

i did some research and on the parts break down the 9.9 and the15 have the same part#.there is a screw on the cam arm that pushes the throttel that is adjusted so the carb only opens up to 3/4,could this be the diff in the hp?there is adjustment to full throttel on this screw.but can you cut the head?bump up timing?open exaust?i normaly work on merc v6,s and that is what i do to them.any info would help,do racers us this motor?what do they do?or is it some secret.

[fbref5269]

the difference in the 9.9 and the 15 is the carb. i sat with a johnson dealer a few years back and the block, crankcase, tower, exhaust tube all have the same part number for both the 9.9 and the 15. the only difference is the carb. and the difference is the 9.9 carb opening in the back is 7/8" and the 15 opening in the back is 1". not much of a difference.

frank

[whaledog]

with a 15 hp carburator the 15 motor turns 6,000 rpm rated.
the 9.9 hp motor is restricted by the carburator size turns only 5,000 rpm.
this is a factory stock rated rpm for horsepower.If you raise compression and rpm you will make more horsepower .

[VINTAGEVECTOR225]

thanks,how much can you cut head and still run pump gas?and how far can you advance the timing?

[Skoontz]

Before you just take any random number, find out exactly what the engines clearances are. Remove the head, and take some modeling clay and place it on in the top of the head. Torque the head with the gasket, then remove it. Measure the thickness of the clay using a micrometer. Some heads we have only been able to cut .040, others we cut .100. Depends on what you have.

[one eight-w]

Sounds like we have an unlimited budget. So while we're at it, why not bore it over, port it, ceramic coat, cut the head, balance the rotating assembly, lighten the flywheel, etc. And since it is going back on an inflatable, I assume we need a stock gearcase. Have you tried any different props? There are lots of things you could do, but realistically, the carb change is the only thing you will notice, the rest is, in my opinion, wasting time and money.

[VINTAGEVECTOR225]

thanks,i think i will leave the timing and head alone,the parts break down i looked at had the same part#between the 9.9 and the 15 unless i was looking at wrong,this is not an unlimited budget the guy i am rebuilding was wondering if there was a few things i could do to it to make it run better than stock.he has a 10pitch prop on it and it ran 22mph before the thermostat broke and pluged off the water inlet to the motor and overheated.if this was a v6 merc i know exactley what to do to make it run.the prop book i looked at did not have a prop bigger than a 10pitch.

[Skoontz]

Solas has an 11" pitch stainless prop for a /
'74 and newer (thru hub) OMC for $295.00.

[VINTAGEVECTOR225]

any one have a 15hp carb?

[Skoontz]

make 15HP, why not find a good guy with a flow bench and bore the 7/8" carb to 1", add a butterfly and you got it.... New 15HP carbs are $175 a piece.....

[VINTAGEVECTOR225]

make 15HP, why not find a good guy with a flow bench and bore the 7/8" carb to 1", add a butterfly and you got it.... New 15HP carbs are $175 a piece.....
where do find a 15 butterfly?

[Skoontz]

Get a piece of brass shim stock the thickness you need, and have it machined. Probably about 50-$100.00....Or, start looking at lawn mower carbs, I would say 18-25 HP Kohlers, or Briggs motors. They will have the size butterfly you are looking for, or at least be a good spot to start looking.

[one eight-w]

First off, what year is the motor?

Secondly, if you are going to spend that much time and money TRYING to make something work, go on ebay and spend $75 and get the one that is for the model year you are looking for. Mid 70's-early 90's will fit many years, and they are interchangable.

You are not being given the best advice trying to finagle one yourself.

[one eight-w]

--------------------------------------------------------------------------------

TRY EBAY>>>

Item # 300157559057

Item # 200158930593 Looks a bit rusty, I would stay away from this one.

Item # 330170905314

I found the year in another post. All of them would bolt on with NO internal modifications.

[David Mason]

Given the J engine is basically the A Stock rules under a different category, I doybt making your own butterfly would be legal ? Not that it would be a speed advantage if you copied stock specs, just not legal. Kind of like painting the gearbox, you can't.

[one eight-w]

David-
You certainly CAN paint an A or J gearcase. That is how they were recieved from the factory.
From the stock inspection man.

OMC A ENGINE SPECIFICATIONS (CLASS A)
It is the intent of the Stock Outboard Commission that the engine in this class be raced as
received from the manufacturer, without modification. Following is a list of restrictions,
descriptions, and modifications, which apply to this engine.
1. It is permissible to leave the gearcase unpainted (bare Aluminum). Unpainted
gearcases may be polished.

I believe that they are using this motor to play with on an Inflatable, not race. At least that is what I can figure out from the first few posts. I don't think homemade butterflies would pass a Stock inspection.

[jtb]

David-
You certainly CAN paint an A or J gearcase. That is how they were recieved from the factory.
From the stock inspection man.

OMC A ENGINE SPECIFICATIONS (CLASS A)
It is the intent of the Stock Outboard Commission that the engine in this class be raced as
received from the manufacturer, without modification. Following is a list of restrictions,
descriptions, and modifications, which apply to this engine.
1. It is permissible to leave the gearcase unpainted (bare Aluminum). Unpainted
gearcases may be polished.

I believe that they are using this motor to play with on an Inflatable, not race. At least that is what I can figure out from the first few posts. I don't think homemade butterflies would pass a Stock inspection.

stamped # 397635 & 388275 and earlyer sand cast carbs that fit the specs are the only legal carbs

[VINTAGEVECTOR225]

the motor is a 1992,and it is going on a inflatable,it is not going to be raced,what kind of clearance should i look for to cut the head?on my snowmobiels and quad morors i cut them for .60 squish.i found a carb at a local boat shop,and waiting for a pm for one at a better deal.would it be ok to set the timing @ 20degrees

[jtb]

just checked in my shop and I do have a carb you may be interested in P/N 398024
PM me if interested.

JT

[VINTAGEVECTOR225]

i think i found one local,thanks guys for all the info.