boring

[14dar]

I have a 25hp want to bore it out to a 35 hp does anybody know bore size of a 35hp

 

[metriccrescentwrench]

Re: boring

I'd be really really surprised if that's all there is to it. To up the HP you're likely also looking at changing the porting, maybe bigger carbs (which would require re-jetting), etc. etc. In general the easiest way to get a significant percentage increase in HP (you're asking for a 40% increase) from an engine is to sell it and buy a bigger one.

 

[tomhath]

Re: boring

In general the easiest way to get a significant percentage increase in HP (you're asking for a 40% increase) from an engine is to sell it and buy a bigger one.

I recall a question on another forum about how to increase the weight carrying capacity of a trailer. Same answer as here - sell it and buy a bigger one.

 

[boobie]

Re: boring

agreed +1. Don't mess with it and get a bigger motor.

 

[kbait]

Re: boring

Depending on the year of your motor, you may increase a 25hp w/carb change. Some years in the '80's used a 35 powerhead and de-tuned for 25hp, and 20hp canadian.. What's your model number? I swapped carbs on a 20hp canadian johnson (french language motor) to a 35hp, and it worked great w/much more hp.

 

[14dar]

Re: boring

Thanks for the replys it's a 3 cyl 2000 all the different is jets in carb pistons and head bore size is what I don't know

 

[14dar]

Re: boring

Also wish I could buy bigger motor buut I belong 25hp club nothing bigger just trying to make this one faster

 

[kbait]

Re: boring

Here's a link to part numbers.. you can compare parts for different hp models: Johnson Evinrude Outboard Motor Parts by Year 1955 to 2011

 

[daselbee]

Re: boring

From the 2000 25/35 Johnson service manual, 3 cylinder inline:

25 HP:
Displacement = 30.5 cu in. (500cc)
Bore = 2.350 in.
Stroke = 2.344 in.

35 HP:
Displacement = 34.5 cu in. (565cc)
Bore = 2.500 in.
Stroke = 2.344 in.

Block might be different, pistons are only available from Evinrude (I have not found an aftermarket supplier), carbs probably will be a larger bore.
Same gear ratio on lower unit for both, same crank.

 

[F_R]

Re: boring

So, you will be boring it .150" oversize (.075" per side). Make sure the cylinder liners are thick enough to safely take that much out before proceeding. Maybe they are, maybe they aren't, I don't know.

 

[ronward]

Re: boring

So, you will be boring it .150" oversize (.075" per side). Make sure the cylinder liners are thick enough to safely take that much out before proceeding. Maybe they are, maybe they aren't, I don't know.

With a car or truck motor boring is measured in THOUSAND'ths. Not fractions of an inch. What you are saying is more than 1/8 inch. I seriously doubt you could do that and get any reliability. I would guess that a 35 has more material around the cylinders than a 25 to allow for the larger bore.

 

[Faztbullet]

Re: boring

lLikey need to be resleeved with larger sleeve

 

[ronward]

Re: boring

10 pounds of sh-- in a 5 pound bag............. can't work

 

[ronward]

Re: boring

10 pounds of sh-- in a 5 pound bag............. can't work

I am just starting to get into boat motors but I DO know car motors...you can only go so far before you sacrifice reliability and longevity

 

[F_R]

Re: boring

Also wish I could buy bigger motor buut I belong 25hp club nothing bigger just trying to make this one faster

This statement has been on my mind all afternoon. You belong to a "25hp club"?? Does that mean you are not permitted to run more than 25hp? If so, what you are thinking of doing---isn't that somewhat immoral? Kind of like a church member living in sin? Will you be embarrassed and shunned when caught? Hey, I don't care what you do, it's your life. Just sayin......

 

[boobie]

Re: boring

Buy a 35 and put the 25 hood on it.

 

[14dar]

Re: boring

Well thank u everybody for Ur inputs I have done a lot of research on this I've got two 3cyl 25 Johnson as I said earlier that is the only different between the two block the same different sleeves carbs saame different jets port size same crank same rods pistons different heads different so I do thank everyone

 

[14dar]

Re: boring

As for the gentleman about sin in at club right now are 3 mega reds this is a factory motor but it has a 50 under the cowl 2 Suzuki 3 cyl rework so I guess we're all sinners

 

[nwcove]

Re: boring

lol.....did the same thing many years ago with a johndeere snowmobile....the crank tag and decals showed as a 340cc, but it was really a 440cc bored 60 over. kept it a secret for years!! tons of fun running against the guys! my lil "340" kickin ***!

 

[racerone]

Re: boring

This should be an easy project.--------Some negative posts by some folks who are not familiar with the 25 / 35 HP triple.---These motors are " heavy duty " and have a shorter version of the 70 HP crankshaft !--They have the same main bearings as the 70 HP triple too !----So go ahead and open it out to the 35 HP bore and enjoy this wonderful motor.--PS I own about 7 of these motors and have rebuilt more than one of them !