any one modded a 25hp merc?

[ber1023]

has anyone modified a 25hp merc? from the 1990's with the 2.25 gear ratio

[genea01]

what kinda boat u running it on

[ber1023]

a winrace from Europe hopefully, www.winrace.no/index_eng.php

[JohnsonM50]

a winrace from Europe hopefully, www.winrace.no/index_eng.php
Is this one yours? [lake Hopatcong last fall]
http://i35.photobucket.com/albums/d151/mes355/8921_1120607424525_1507256635_30287.jpg
Theres several ways to look at making it faster. 1, Setup of motor/boat, height, angle, weight & its distribution. 2, Prop choice, a general prop made for the motor might not be working to potential. Luckily Merc offered performance options but a custom prop may be needed. 3, HP/RPM. mods can always be done but with 2 1/4 : 1, if you got 1,000 more R's out of the powerhead it would add up to about 5 MPH if you were using a 13" pitch prop. Larger pitch could increase that a little but its easy to over pitch a small motor & lose performance. Its being a deep V [?] is hard for the motor, they can be fast but it takes more.

[ber1023]

no, same boat though I live in Bermuda. Yeah ill have winrace prop and the boat set up properly i just want to mod engine!

[Fastjeff57]

IF your block has the word "Mercosil" cast into it (upside down and on the right rear side) then it can be safely ported. (The earlier, chrome or nickel plated bores are "iffy" since the plating can peel away.) Since the heads don't come off, any raising of the exhaust port will result in a loss of compression ratio, but that motor is very mildly ported so.... I'd say it's worth a try.

I can tell you from my own Merc 25 experiments that merely slapping a larger carb on does very little.

Jeff

PS: Nice boats!

[JohnsonM50]

IF your block has the word "Mercosil" cast into it (upside down and on the right rear side) then it can be safely ported. (The earlier, chrome or nickel plated bores are "iffy" since the plating can peel away.) Since the heads don't come off, any raising of the exhaust port will result in a loss of compression ratio, but that motor is very mildly ported so.... I'd say it's worth a try.

I can tell you from my own Merc 25 experiments that merely slapping a larger carb on does very little.

Jeff

PS: Nice boats!
It can be looked at as HP per CI. you can increase HP on the same CI's by trading off low end power. Motorcycles can run well with incredible HP per CI because of 4,5,or 6 gears. Outboards need the low end so while maybe not hi performance in comparison at least performance engineered. Stock Race outboards give a little more power at the motor usually but the reduction of running friction & spinning a smaller prop at higher RPM's is what makes them work. If you went that direction you might gain 10, 12 MPH's [give or take] The 1 in the pic is real nice, great cockpit & looks like alot of fun but the typical varied wood hydro's runabouts there were faster.

[ber1023]

it doesnt have "merosil" on it, whats the best motor in this size and weight range to modify and get the most power?

[genea01]

what is the ci range int he rules

[ber1023]

no rules, im not racing its just pleasure basicaly. All racing in bermuda has died out more or less

[genea01]

if there is no rules then slap a 3cyl yammie on it but you can get the merc to run very good, if you are running mostly just top end slap you a 11x20 cleaver on it

[ber1023]

do they weight much more than 112lbs , as that wat the merc is and probably near the limit on weight. Id expect just over 50 with a 25hp.

[YAMAHAFASTCRAFT]

there weight is around 120 i think. you can do some serious mod. to that motor.

[50hptiller]

run the old style crank if you can its a lil lighter, lighten flywheel a little, lwp, several years ago a friend made some inserts to go in the combustion chamber to tighten it up, find you a horn, big carb, and a big cleaver........or find a 45sst motor and hang on for dear life.

[hydroplay]

Have seen a 25 Merc motor that Del Snyder built that had a removable cylinder head for more compression, some work on the ports and an external exhaust with a Konig Y-pipe manifold and an old Konig pipe. It ran well but eventually was sold to someone in Lousiana for use in jon boat races. Lots can be done if you are serious. Chrome bore can be ported and re-chromed.

[ber1023]

not that serious, how about a 30 johnson?? the 2 cylinder ones

[genea01]

not that serious, how about a 30 johnson?? the 2 cylinder ones


it is easier to get more hp out of the 31ci omc than the merc

[Seagull 170]

You'd better tell them about the water conditions you plan to run this in.

Not a lot of flat fresh water in Bermuda, (only in swimming pools) 40mph on south shore might be a very rough wet ride!

[MWhite]

Is this one yours? [lake Hopatcong last fall]
http://i35.photobucket.com/albums/d151/mes355/8921_1120607424525_1507256635_30287.jpg
Theres several ways to look at making it faster. 1, Setup of motor/boat, height, angle, weight & its distribution. 2, Prop choice, a general prop made for the motor might not be working to potential. Luckily Merc offered performance options but a custom prop may be needed. 3, HP/RPM. mods can always be done but with 2 1/4 : 1, if you got 1,000 more R's out of the powerhead it would add up to about 5 MPH if you were using a 13" pitch prop. Larger pitch could increase that a little but its easy to over pitch a small motor & lose performance. Its being a deep V [?] is hard for the motor, they can be fast but it takes more.
man,



Man, I would like to run my 40 merc on that boat.

[JohnsonM50]

man,



Man, I would like to run my 40 merc on that boat.
Ive seen it a couple times, its really something. I didnt get to meet the owner tho. A 40 would be 'considered' to be too big sure but imagine that & a good speed prop. Some deep vees ride on a pad planed off, dont know whether these are v thru-out or padded.

[MWhite]

Ive seen it a couple times, its really something. I didnt get to meet the owner tho. A 40 would be 'considered' to be too big sure but imagine that & a good speed prop. Some deep vees ride on a pad planed off, dont know whether these are v thru-out or padded.

Hey, man that thing is cool looking, what kind of boat is that, name brand. I could make a 40 fly on that.

[JohnsonM50]

Hey, man that thing is cool looking, what kind of boat is that, name brand. I could make a 40 fly on that.Its a Win Race, I think made in England. :cool:

[DonChichoJr.]

I Have One, 1995, Mercosil., With A Set Of Wiseco, 0.040" Pistons,
The Intake Was Ported And The Reed Cage Was Laped & Ported Using A Set Of Boyesen . The Exhaust Releiving Holes Was Tapped At The Exhaust Plate. The Two Coils Are "echlin", Made In Germany .
The Prop Is A Turbo 1 .
Really The Engine Run Very Strong, Using A 93 Octane Gas With A
Pennzoils Synthetic Blend Oil At 40/1 .

Thanks,:d
Boat Doctor