eska 9.9 to a 15hp?

N

narwhals

Petty Officer 2nd Class
Joined
Jun 19, 2011
Messages
154
i started a couple weeks ago talking to some wise individuals about the diferrences of a 9.9 and a 15 hp eska. upon further research the bore and stroke are the same and it looks like changing out the high speed jet should increase the hp by increasing the rpm's.the only question is do i have the right jet 631811? the 385C engine shows a 631833 or a 632072,the 631811 goes to a 381A engine, carb 631740A. i won't know until i get out on the water and change out the jets to see if there is any difference. the original jet has a larger horizontal opening but a smaller vertical opening than the replacement jet. i wish i had a tachometer to check and see if there is any difference. does anyone know enough about the numbers i've listed that i have the correct high speed jet for this to be successful or a complete failure?:rolleyes:
 
M

mrcrabs

Guest
Re: eska 9.9 to a 15hp?

All I can say is I have the 631811 jet and the 381A engine @ 15hp, if you ever pull the power head we can compair exhaust ports, proping makes a big dif in all of this as well, what pitch do you have on the 9.9? I think they cam with 11p and the 15 had a 12p.


I put a 12p from the 15 on my 7.5 deluxe yesterday just for fun and it came to half power @ WOT barely, I thought I was trolling out of the marina at a good clip and when I hit the river and went for WOT I realized heck I was already there ....LOL
 
N

narwhals

Petty Officer 2nd Class
Joined
Jun 19, 2011
Messages
154
Re: eska 9.9 to a 15hp?

thanks for the feed back on the numbers, i've got a 8 1/4 x 11p prop on the unit . i got a reel good look at it this weekend when my sucker wrapped itself and the steel leader around the inside of it, i had to remove the prop while on the water to get it untangled. murphy really kicked my ***** this weekend...LOL i'll see if i can find a 12p prop for it to help it out as well. thanks again.
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: eska 9.9 to a 15hp?

Changing the jet size can increase the amount of fuel available, but unless you also increase the amount of air you will end up with a bad running gas hog.

Good way to ruin a good engine.
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: eska 9.9 to a 15hp?

Is the timing of the rotary valve the same? We used to modify the rotary valves in big Homelite chainsaw engines (on racing karts) to get significant power increases.
 
M

mrcrabs

Guest
Re: eska 9.9 to a 15hp?

Good question JB hadn't thought of that. The rotory vave is part of the crankshaft so I should be able to cross check the part numbers and .......searching.....I find the crank is the same no. but that 9.9 block half is a diffrenet number. So just in theory the rotory port could be larger and still use the same crank? , I'm guessing alot here but the timing has got to be the same unless there is a way to modify the port and retain the crank size??? I just don't know....But I'm almost sure that this whole horse power thing is all marketing gimicks anyway with the Eska twin. Same as the johnnyrude 9.9 & 15,

I say just changing the hood is all you really need to do....LOL
 
T

todd ashley peters

Seaman
Joined
Nov 7, 2010
Messages
56
Re: eska 9.9 to a 15hp?

Good day gents. There are a few things that i have noticed about 9.9 vs 15.

1. the hole in the carb body is bigger by a fair bit.
2. the air intake in the engine block is also bigger.
3. larger holes in the high speed jet.
4. the piston rings are slightly higher on piston in the 15.
5. larger volume fuel pump.

one thing that someone mentioned is the exhaust ports. i've never compaired them, but i am curious. i'm about to strip another 9.9 and when i get it apart i'll measure them. thinking you should get 12 or 13 hp by using a 15 carb, pluging the vac hole, drilling out the spigget, srewing in a barb and using a remote aftermarket fuel pump. maybe 14 hp if you enlarge the air intake in the block.
 
M

mrcrabs

Guest
Re: eska 9.9 to a 15hp?

my 15hp has the same fuel pump as a 4.5hp Eska,

drilling out the spigget, srewing in a barb and using a remote aftermarket fuel pump.
Click to expand...

what pump do you use and where do you drill? and are there any issues with just closing off the pump element hole and do we need to do anything else around the flapper valve...just take it out?? I did notice on the 7.5s that the fuel pump elemnt hole in the carb could be sealed with a welch plug.

I measured the venturi tonight on a 7.5 and the 15 just for fun...the 15 has a big ole hole. Wow :D
 
N

narwhals

Petty Officer 2nd Class
Joined
Jun 19, 2011
Messages
154
Re: eska 9.9 to a 15hp?

so based upon all the info written am i barking up the wrong tree? i noticed on a few websites that it looked like everything was the same except for the rpms being higher on the 15. change the jetting as discussed should increase the rpm's as i've seen that on many lawn engines that bigger jet increases the hp. you mentioned staying with the 11p prop and not going with the 12p, would i be gorping too much water to get the engines rpm's up? i do want to get a new prop as the old has a pretty good gouge off of the tip of a blade. 11p or 12p or not to p. i tried going to sears link and came up bupkus for me. thanks guys for all the feedback.
 
M

mrcrabs

Guest
Re: eska 9.9 to a 15hp?

I guess the higher rings give a bit more more compression, bigger venturi and jet, larger carb hole on the block, and yep the 12p would take the rpm down....we are learning here....thats a good thing.

check with indy boat for that prop they are the authorized parts dist for CPC

http://www.boatsportandtackle.com/servlet/StoreFront
 
T

todd ashley peters

Seaman
Joined
Nov 7, 2010
Messages
56
Re: eska 9.9 to a 15hp?

View attachment 115126View attachment 115126View attachment 115136View attachment 115137View attachment 115138View attachment 115139hi guys, here's an original 15 hp carb with the side mount carb.by the way i have no idea what i'm doing on a computer. i ment to use a 15 carb on the 9.9, thats why i mentioned blocking the bladder hole off.to do that just make a gasket like the one shown except don't put the bladder hole in it. the vac hole would be drilled in the spiggot with the red dot, and put a barb in that hole. the remote fuel pump is like the one shown on the green ob under the pull start and the ss piece is the adapter for the remote pump.the other pic of the 15 carb shows the barb that comes from the pump
 
M

mrcrabs

Guest
Re: eska 9.9 to a 15hp?

Heres a hard left turn for you but I thought you guys might want to know,
So I found that the recoil starter gears and recoil spring and cover are the same as a old toro mower, I just bought one on a seconed chance offer from ebay for 12$ brand new, the bracket will not work with our twins but every thing else is there to make you brand new. Tecumseh part no 590450A and I found another for $45....consider that the part the spring and rope goes in will cost you 25$ plus shipping from sears and the break about $2 and the gear there asking 45$ alone if you can even find one plus you get abrand new recoil spring and rope.

I have mine on the bench, I just need to change it over to the Eska bracket

http://www.ebay.com/itm/NEW-TECUMSEH-NOS-RECOIL-STARTER-ASSEMBLY-590450A-/180683223502


24$ but its missing the brake...a 2$ part, edit: oops its out of stock
http://www.usedpowerequipmentparts.com/servlet/the-1595/Tecumseh-Toro-Starter-590450A/Detail
 
N

narwhals

Petty Officer 2nd Class
Joined
Jun 19, 2011
Messages
154
Re: eska 9.9 to a 15hp?

i checked out boat sport and tackle the other day and saw they had both props in stock. i'm going to change out the jet to see if it makes a difference in rpm's. i need to get my hands on a tachometer to really see if there is an increase in the rpm's. too bad there isn't a powerband in the eskas like there was in the old YZ-250, better have a good grip on the bars or it could really be trouble. fifth gear wide open across a farm field is completely different than wot on the water with a 9.9. LOL i guess i'll need to get a much larger engine if i want that feeling.
 
M

mrcrabs

Guest
Re: eska 9.9 to a 15hp?

better have a good grip on the bars or it could really be trouble
Click to expand...

I remember, oh how well, my first ride I had to ease out of the little counry village I lived in and when I crossed the bridge over Bay creek I let her lose....at first I thought Ok its just another 250.......then something magical but scary happend....Zoooooooooooooooooooooooooooooooooooooooooooooooooom!!!!!!!!!!!!!!!! we were go at full throttle up, gear again gear again etc etc ....zoom zoom zoom zoom.....about 1984-6ish ??? can't remember exactly.
I sold it to a guy on half down and the rest in 30 days, its been almost 30yrs and never got the other half of my money.
 
N

narwhals

Petty Officer 2nd Class
Joined
Jun 19, 2011
Messages
154
Re: eska 9.9 to a 15hp?

mine was nicknamed the screaming yellow banana, also a mid 80's, i think one of the first years they had the powervalve in the motor.i used to race cross country events until i screwed my back up at work 6 years ago.there was a guy on a brand new 400 KTM that would get me everytime in the woods,but as soon as we got to the farm fields it was bye bye to the orange machine.he came up to me after the race and couldn't believe he was getting his lunch handed to him by a bike 20 years older than his. ah the good old days, now i'm just a lowly fisherman playing with my eska LOL. sorry to here you got stiffed for the other half.
 
M

mrcrabs

Guest
Re: eska 9.9 to a 15hp?

my best friend was riding mine and jumped the railroad tracks near the bridge, got a bit sideways and caught a 1956 chevy picukps head light bucket with his left big toe....needless to say he lost that big toe.
 
You must log in or register to reply here.
Top