Mod 25hp Johnson

[RACINCRABBER]

Out of curiousity, How could one modify a lil 25 hp JohnnyRude mota? Say make it a 35 or 40

[half fast]

Apx. Ten to fifteen horse shot of nitrous...... Maybe shave the head,boyson reeds dry the exhaust out.The nitrous sounds easy to me . hf

[Laker]

I have a 78 35hp .. when the raiting went to the prop shaft that motor became a 25 and my 35 performs like a 25..
Later they came out with the 30hp Xflow twin and that motor is MUCH stronger than the 25 or old 35.
i would start by finding out what the difference is.
I have never gotten a good answer or been able to look inside a newer 30 but I have heard the ports, intake and head are all different.
If a 25/35 can be built to run as hard as a newer 30 I would do that and raise the compression up as high as you can.

[RACINCRABBER]

I'm not lookin to make a drag boat out of my flatboat i just wanna be able to beat my neighbors 25 Yamamahaluler 4stroke on top end i jus want a few tricks to like the carb or timing.:D since i cant let a 4 stroke beat me

[Looper]

Is it a 2 or 3 cylinder? I've got a 2000 3 cylinder 25 that Bomb discontinued. Lots of torque, got it on a 16' Carolina skiff, 29 or so on GPS trimmed out. :D

Great holeshot, It'll slide you right off the seat if you don't hold on.

Been thinking of adding some setback. j/k, sort of.

I think the 3 cylinder would be easy to get 30 hp out of it, but it is a lot heavier than the lightweight twin.

[airide18]

What year is the engine????

[RACINCRABBER]

its a '99 2 cylinder it runs about 32 mph :D on GPS thats hoppin and porpisein im running a stilleto 10 1/8 x 14 pitch . Do they make like a small chopper prop for something like that? :confused:

[David_L6]

when a larger motor would be a lot easier.

Call Hopkins props and talk to them about what you are trying to do. They can probably help you out with your prop. www.hopkinsprops.com

Mill the head, drill out the reed plate holes a little, open up the stops a little. That's about all I can think of to do to the motor that is practical other than making sure you have a good bore and good ring seal so you aren't losing ground from the start.

It's been said many times before, but set up and testing...

[Laker]

how about this?
little chopper is for a merc 25....
Very hard to find but works great!

[Forkin' Crazy]

I think all you need will be a carb for a 30. Price around for some and I'll see if I cannot get you a better deal!:) (my buddy is a dealer)

David_L6, some places down here the largest motor you can run is a 25, but that is mostly federal reserves.

[airide18]

Ive got a merc 10 3/8 x 18 mini chopper for sale if your interested,out of 10 mini choppers ive ran on my boat with a 25merc this one was the fastest and the only one i have left,its the older style with a smaller hub,the ones with the bigger hubs(newer ones) are not as compatable as the smaller hubed ones,i have have had a johnson 25 hub in it a few times when i was trading it around with my freind and i used his New chopper II and it was 5mph slower than the one i had....If your interested email me at [email protected] .

[RACINCRABBER]

I could probably get jus da jets and put in the carb i already got?
I think I can get dem
thanx

[Forkin' Crazy]

Nope, that won't work. Your carb is jetted to it's size (size of the venturi). The 30/35 hp carb is larger and flows more air, as well as fuel.



:cool:

[airide18]

On my freinds 1985 25hp johnson we modified a 50hp carb for it and gaind quite a bit of HP....

[David_L6]

Originally posted by Forkin' Crazy

David_L6, some places down here the largest motor you can run is a 25, but that is mostly federal reserves.

That's why replacement cowling decals are sold, isn't it? ;)

Whatcha mean down here? I'm due west of you (just north of Shreveport). :)

[airide18]

Thats gotta suck if thats the biggest mota you can get>>>>>:(

[wing nut]

"sir thats a mighty big 25hp eninge you have there.. with 6 cylinders and all.."

"but officer its only a 25hp.. it says so there on the cover :rolleyes: "

LOL

[airide18]

Yeah i heard about one of those,its one of those 4.5hp per cylinder 6 cly.:D :rolleyes:

[Forkin' Crazy]

Originally posted by David_L6
That's why replacement cowling decals are sold, isn't it? ;)

Whatcha mean down here? I'm due west of you (just north of Shreveport). :)

OOOPS, sorry, no offence....;) I was really refering to the marshes and stuff down in south LA and MS.



:D

[David_L6]

Originally posted by Forkin' Crazy
OOOPS, sorry, no offence....;) I was really refering to the marshes and stuff down in south LA and MS.



:D

Just messin' with ya!:cool:

[MODIFIEDOUTBOARD]

The OMC 25hp is raced in APBA.
There are some folks that could help with 25 performance.

When it is rebuild time drop me a line it is not that difficult to port the old cross flow omc twins.

Anthony McCulloch

[RACINCRABBER]

down round here u can run any size mota u want i got a 15ft stream with a 140 , the only thing dey say is , is dat thing fast?

[airide18]

Theres no HP or speed restrictions where i live.....:D Thank God

[wing nut]

same here.. i think.. well if there is no1 follows them! lol

[airide18]

Yeah if we had speed or HP restrictions down here they wouldnt last long4er than a week.:cool: