Extract more hp from Merc 30hp 2cyl 2 stroke

[wolfgangb]

Yes, this is an odd one: we have a local juniors class in which predominantly recent 30 hp Merc 2 strokes (2 cylinders) are run.
Hp/rpm differences between competitors appear to be up to 15%. My buddy`s children are running in that class and i would like to help them improve their competitiveness.
Any advice appreciated, before we spend big bucks leading ourselves down the garden path.
Thanks guys,
Wolfgang (South Africa)

[FMP]

I bit off topic but a 3 cylinder in that 25-30hp range was made for a few years. Force by Merc, called an international model the last couple years. Maybe more potential?

[phillnjack]

no such thing as force by mercury. it was just that mercury bought out the force brand... once all stocks were used up and the factory shut down it
stopped being made.
force were low grade motors made on the cheap, they were good for the money and thats about it.

the mercury 30hp will out perform the force every day of the week, it was made by tohatsu and is a brilliant motor that can be modified to give some very high performance.
But I would think if you have a 30hp category then you will be limited to the mods your allowed, if the class is by the engine capacity then you can modify it
and get a lot of power from the motor.
check out the gt30 race class and speeds.

just noticed your in south Africa, this makes it even better as you have plenty of spares for the tohatsu/mercury /mainer 30hp motors.
a force in those parts would be a terrible idea, no parts back up at all....
all the Asian market motors and mods are available to you, depends on how far you8 want to go and what the class allows...

[FMP]

https://www.youtube.com/watch?v=5yX7FEFU2Xs
you again
https://www.smalloutboards.com/images/f2597l/inside1.jpg
https://www.smalloutboards.com/images/f2597l/serial.jpg
92 lbs triple 6000+rpm range, merc lower

[Capt.Insane-o]

https://www.youtube.com/watch?v=5yX7FEFU2Xs
you again
https://www.smalloutboards.com/images/f2597l/inside1.jpg
https://www.smalloutboards.com/images/f2597l/serial.jpg
92 lbs triple 6000+rpm range, merc lower

The Force actually ran pretty good and the 18 chopper slides right on the shaft.

The big actual Merc 30 is a heavy poor idling turd. It has a single carb and shares all the internals with the 40-60 triples so you could cut up a triple intake to make it a two carb.

If you have the Tohatsury it's a different animal.

[FMP]

I noticed that tohatsaboo with yet another brand name on it, Korean or Malaysian i think. Who made who, ain't nobody told you.

[phillnjack]

its a force.. force is just the company that mercury owned for a few years till they dropped it in 1996...due to lack of interest in cheapo motors.
you can put whatever stickers on it you like, its still just a force.

a rolls Royce used Lucas electrics, borg warner gearbox, Citroen suspension and bodies made by various companies, but it was still a Rolls Royce.
Today Jaguar is owned by Tata but its still a jaguar as too is Land Rover, but everyone still considers them to be English motor cars not Indian.

the original poster has a far better motor in his 2 cylinder mercury 30hp, it will always be easier for parts availability anywhere in the world.
parts for mercury, mariner and tohatsu are in all 4 corners of the planet.
plenty of after market modification parts i.e reeds available for the mercury as too are props water pump kits, carb kits etc.
and power wise it will destroy the force triple, power to weight goes right out the window on this application.
the merc twin is around 15 pounds heavier, but its weight is its quality....

[phillnjack]

merc 25 and 30 for a long time have been the tohatsu motor.
the other brand name for tohatsu is Nissan, they are nothing like the Malaysian or Korean crap copy motors like hidea etc.

Tohatsu /Nissan is the same motor. different name for different countries.

if you ran a tohatsu you would then understand just how bloody good they are. very strong and bullet proof motors. and very quick.

people all around the world racing the their 50hp motors in the salt and getting them dunked a lot on the zap cats.
more fisherman in the world buy tohatsu/nissan than any other brand.

the Nissan tohatsu have been used by mercury since the late 1980's on their small motors, I have a 1990 4hp branded as mercury with the mercury decals
and the Brunswick /mercury decal.

[FMP]

I think your 4 could be a Force, lol

[Capt.Insane-o]

30 hp mercury weighs 170 lbs.
30 hp Tohatsury is 120 ish pounds

still don't know if he has a real Merc or a rebadge.

[wolfgangb]

Hi, Thank you all for your interesting comments. The class is our local GT30 variant, and it appears now that all and any mods are allowed (politics again). As stated by the local Merc importer, the heavy turds (apt expression!) are indeed Tohatsu manufactured. It does have some unusual features, like a built-up crank (con rod big ends not parted), a totally useless inlet tract with uneven mixture distribution (the standard motor uses a slotted restrictor plate between carb and manifold to overcome this), loads of dead volume between the reeds and the crankcase proper, hence next to no pre-compression. The standard Keihin carb does not even allow adjustment of the float level!
The suggestion to cut up an original triple sounds appealing and doable (even here) and much better than trying to make a purse out of a sow`s ear! After all, Renato Molinari had Autodelta cut a Twister apart to win the SE world championships after protesting Michael Werner`s win with his handbuilt Mercury triple), was it beginning seventies?
Please keep this great thread going, and thank you again for your valuable contributions.
Rgds, Wolfgang

[wolfgangb]

On another note, I am actually a great West Bend, Chrysler, Force fan. That goes back to the `60s, when as a youngster I worked for the German Chrysler Marine importer. I do own a `93 5 cyl Force, being fitted with 5 carbs from a 98 model 90hp Force and a CLE, plus a 98 model 120hp, being fitted with carbs from a 140hp Johnson. I do own the long and short original Chrysler racing lu`s, and did shorten Chrysler tower housings to fit them to both motors. And yes, had an adapter fabricated to fit the Chrysler rlu to the 120hp mercurized Force. Of note is that Mercury after the `95 acquisition of Force expended considerable resources to modernize and upgrade the Force motors with increased bearing sizes, improved electronics etc., only to close them down when design-wise they had reached optimum maturity!
For racing, i am preparing for next year an STV replica, with an upgraded 280XS, with 2to1 and a 1,87to1 Sportmasters. I also collected a 2,4 chrome bore Merc V6 of unknown age. it has an unpainted block and 2-piece cylinder heads with widely-spaced bolts - appears to be an ancient Mod-VP block. Bores are undamaged, although 3 pistons lost their ring-lands. I need more garages LOL, the older I get.
Rgds, Wolfgang

[FMP]

I thought I recognized your name from another site , I remember reading about a fuel injection you had been thinking about building for the Force. Please share some details on all the builds , F5 5 carb included.

[Capt.Insane-o]

Right, you have a Tohatsury. The US version of the 30 hp is the heavy turd.

This spring I was brought a 1978 time capsule Starcraft with a like new Chrysler 105. After some ignition upgrades and service it was probably one of best running motors I got in this year. Quiet, started instantly and ran incredibly well. The young guy was tickled to death as it was his gramps boat. He and his girlfriend logged a bunch of time in it this summer, pretty cool.

[staylor]

For the record- the original firm was Kissel which became West Bend(who made Elgins under a private branding with Sears)- Chrysler- Force. I was given a early 1950s Elgin(West Bend) in the 1980s that was missing a lot of parts. I went to the local Sears store and all the parts I needed were ordered- including small parts like the high speed needle and gaskets. All the parts showed up one at a time thru the mail in little envelopes for around 2 weeks. But I was still missing a prop so I took a flyer and went to a Chrysler outboard dealer. I showed him the motor and he went into his parts and came up with a 6 hp Chrysler prop that was a perfect fit. This little motor ran like a top for the 8 years I owned it after getting it running. Carb had a glass float bowl like an early Holley carb- easily removed with a little clamp when you saw crud building up, then quickly dump the bowl overboard, re-install bowl and clamp and keep on running.....
Doug

[FMP]

I have a great little 12' that would boogie with one of those 92lbers. Need to find one locally. Currently runs a 6Chrylser.

[charlie the wonder dog]

Hi, Thank you all for your interesting comments. The class is our local GT30 variant, and it appears now that all and any mods are allowed (politics again). As stated by the local Merc importer, the heavy turds (apt expression!) are indeed Tohatsu manufactured. It does have some unusual features, like a built-up crank (con rod big ends not parted), a totally useless inlet tract with uneven mixture distribution (the standard motor uses a slotted restrictor plate between carb and manifold to overcome this), loads of dead volume between the reeds and the crankcase proper, hence next to no pre-compression. The standard Keihin carb does not even allow adjustment of the float level!
The suggestion to cut up an original triple sounds appealing and doable (even here) and much better than trying to make a purse out of a sow`s ear! After all, Renato Molinari had Autodelta cut a Twister apart to win the SE world championships after protesting Michael Werner`s win with his handbuilt Mercury triple), was it beginning seventies?
Please keep this great thread going, and thank you again for your valuable contributions.
Rgds, Wolfgang

Have you seen this thread: http://www.screamandfly.com/showthread.php?258534-25hp-merc-boost-up&p=2396210#post2396210

[FMP]

Pretty lofty, 185-200psi out of the box. Don't know of any motor that won't run with punch with that psi.

[Mark75H]

Yes, this is an odd one: we have a local juniors class in which predominantly recent 30 hp Merc 2 strokes (2 cylinders) are run.
Hp/rpm differences between competitors appear to be up to 15%. My buddy`s children are running in that class and i would like to help them improve their competitiveness.
Any advice appreciated, before we spend big bucks leading ourselves down the garden path.
Thanks guys,
Wolfgang (South Africa)

Props and set up will beat hp bumps

[wolfgangb]

I thought I recognized your name from another site , I remember reading about a fuel injection you had been thinking about building for the Force. Please share some details on all the builds , F5 5 carb included.
Sure will do. Presently having special parts produced/machined. Est completion both motors (porting comes later, when I have space in the garage) is March/April next year. Then I will post the photos. The major job on the F5 carb will be the mating of the 3 cylinder crankcase fronts and the line-boring. The rest is easy. Thanks for your interest. Rgds, W

[phillnjack]

the talk of 180 to 200 psi compression on the tohatsu 25/30hp straight out the box is total rubbish.
around 125 psi is fine on the tohatsu/mercury 25/30. head skimming can take the compression to around 150 to 160.
chris carson for a set of sport or race reeds.

but you need to find out the rules on the mods before making any changes.

[phillnjack]

I think your 4 could be a Force, lol

No its 100% a tohatsu re-badged as Mercury.

There is more chance of getting a jew and a muslim together to eat bacon sandwiches and pork pies than getting me to own a force.

I would probably use one if 100% sponsored and did not have to repair it myself.. but only if I could wear a full face crash helmet with
black visor. as could not let any of my friends see me stoop so low, ....


391695

[FMP]

Again, me thinks you do protest too much.

[phillnjack]

No just honest opinion on them... seen many of them broke, raced against them , and never seen a good one.
in the UK 99% of force engines have been stolen off the backs of boats and owners claimed on insurance !!!! :thumbsup:

you seriously cannot get any dealer to buy one...
and cannot get any parts for them over here, there never was any good parts availability even when it was us marine.:mad:

[FMP]

That will make it easy for you , the ones left are winners. Like old Jags over here, once you swapped the motors for a real V8 and rewired the thing to run in the rain they were great.

[charlie the wonder dog]

the talk of 180 to 200 psi compression on the tohatsu 25/30hp straight out the box is total rubbish.
around 125 psi is fine on the tohatsu/mercury 25/30. head skimming can take the compression to around 150 to 160.
chris carson for a set of sport or race reeds.

but you need to find out the rules on the mods before making any changes.

Maybe I've just been freakishly lucky, but of the nine 25C3s I've had of, none ever had compression lower than 150psi after break-in, one had 175psi, one @ 190/195, and another 190/200. Measurements taken by the dealer, then replicated using my own gauge due to disbelief.
Have also been advised by a very successful former racer that in modified form (decked blocked, shaved C2 head) 220psi is achievable.

Maybe we've all got happy compression gauges in Australia.

[FMP]

Do they recommend 92 fuel ?

[phillnjack]

FMP...
the 25/30 made by tohatsu/nissan can be run happily on 89 octane in most climates, their largest sales are in Asia who have very poor low octane fuels and the motors still run good.
and they will also run happily on bio fuels...
the japs are very conscious about fuel emission's, even though their chimneys still pump out soot like the Chinese..

[FMP]

Those 190+ psi stock motors must be marketed to the hightest countries. Going to find a triple F25 and cut and deck to 195, work it some. Bet it walks the tohatsu

[phillnjack]

no its the upside down gauges ha ha

my friend has lovely little 25hp tohatsu running sweet as a nut with its 130 psi and starts like a dream 3 pulls from cold.

[FMP]

I have a 25 merc that's been a 1-2 pull motor since day one. Almost as good as my Chryslers, a good stern stare at the flywheel gets them running.

[NZ Sidewinder]

These motors very in compression.
I've got one with a standard bore that got a light lapping of the head and its 150psi.
Another with plus .020 bore and very light lap of the head, again 150psi.
I've been told they range between 125 and 150psi new

[NZ Sidewinder]

the talk of 180 to 200 psi compression on the tohatsu 25/30hp straight out the box is total rubbish.
around 125 psi is fine on the tohatsu/mercury 25/30. head skimming can take the compression to around 150 to 160.
chris carson for a set of sport or race reeds.

but you need to find out the rules on the mods before making any changes.

I have 4 of these 30hp Tohatsu/ Merc motors.
1 of them has +.020 bore, two of them are std with fresh hone and rings, one is used, std, untouched.

They all have between 140 and 150 psi compression.
The 3 that have been rebuilt have had the heads lapped flat.
You can tell how much has come off the head by looking at the anode recess.
The takeaway is that 150psi is typical for these motors.
I once ran one with a bad coil for about 400m and it bogged down and limped home.
The extra oil in the bores took the psi to 170 but once a new coil was fitted and the engine run again, compression was back to 150psi.


One observation has been that there is a large range of port to casting mis-match.
Of the 4 engines, a 2003 motor has almost perfect match up, a 2015 one has shocking match up and the other one is run of the mill ok, one is unkwown