Dishoner

[B Walker]

Most outboard motors designed and built for non-racing use an impellor in the foot to push water up into the motor for cooling.

After the water runs around the passages in the head and block some is diverted to a "pee hole" so the operator can visually inspect for proper cooling water pumping.

The rest is just dumped into the tower and free flows out the underwater exhaust. In the process of dripping out of the block into the tower it splashes around and cools off the tuned exhaust pipe that is in the tower.

If you plug that passage and force all the water out the pee hole you have created a "dry" tower and a "dry" pipe inside the tower.

A "wet" pipe is significantly less efficient than a "dry" pipe. Its the difference of about 3MPH in a 15HP OMC.

BW

[raceright]

Geeeeeeezyou stock guys know to many illegal tricks

[pirata]

Another thing that has not been mentioned yet, spark plugs? Is it running rich or lean? You want a nice golden brown color on the plug. Looking at the pic that shows the prop, maybe a file to fix the dings in the blade (or blades).

[johnsonm50]

I have a Johnson (96) 3 hp, that is tricked out by Vic Brinkman, that we race once a
year in our 3 Horse Club Race. Run it on a 14 ft narrow bottom jon boat, 2 guys, 2 gals
of gas with squeeze bulb for refueling under way, 2 guys, 12 refreshments, etc, runs
anywhere from 13 mph to 14 mph on gps depending on setup...fuel is 119 octane, Klotz
racing oil, NGK plugs, we weigh in about 400 lbs total for race. we race about six lakes
marathon style..its a blast really..use automatic transmission fluid in gear case..even
have pipes made for this little runner..we have won our class 4 years running..just
saying, anything is possible with these smaller engines..

Ive heard of but haven't seen the 3hp races where nearly anything goes on the motor. There's also 6hp derbies but I think those are stock. If you check with the boys over at AOMCI [ask a member] you might at least read what 6 is the big-un.

[Kev43V]

what if you built a low water pick up? and cut down a J wheel to clear the cavitation plate?

[sam]

The fast 6 the AOMCI guys run is the antique 4 cylinder Zephyr

A J wheel isn't enough prop for a heavier boat

[ricochet112]

Buy a Merc 15 and 6 hp, swap the cowls, bingo, 10 MPH!!!!

Can't tell if your 6HP is a 1977 or 1987, (it looks more like a 1977) your toast for more HP if it's a 1977, the 1987 was a de-tuned 8HP.

[johnsonm50]

Buy a Merc 15 and 6 hp, swap the cowls, bingo, 10 MPH!!!!

Can't tell if your 6HP is a 1977 or 1987, (it looks more like a 1977) your toast for more HP if it's a 1977, the 1987 was a de-tuned 8HP.

The #s are right there on the port clamp right? Just need a closeup & you can find it on BRP, gives you #s to choose from so will be easy to pick year.

[fhafer]

It's not a 1987

I have a 1987 6hp......that looks more like my 1969 6hp.

[johnsonm50]

As far as goes a prop you would need to know what is available to buy & install, what the gear ratio is & whats the max dia [in case you go large] as well as run weight. Dont rule out the hull, altho wax is not recommended for racing, on a much slower tin boat it does help, a smooth shiney waxed bottom [baby] LoLs Assuming for the fun of it money's no object, how fast ya wanna go??

[B Walker]

The fast 6 the AOMCI guys run is the antique 4 cylinder Zephyr

A 4 cylinder 6HP? Thats just crazy talk.

BW

[Kev43V]

didn't OMC make a really small 4 cyc.(bigger than 6hp I am sure) for the navy during world war 2?

[Aqua Zombie]

PBRSpecial... ATF oil in the gear case? Less drag through the gears?

[Aqua Zombie]

Does the skeg need to be there? I've been told there have been gains in cutting those things off, or hacking them down and sharpining them. You can bet that the gear case and prop are going to get some fileing and polishing.

[B Walker]

what if you built a low water pick up? and cut down a J wheel to clear the cavitation plate?

Low water pickup would just eliminate the drag of the impellor which is pretty minimal

As far as props go he would probably do better banging on the aluminum and cupping it a bit. A real performance wheels effect would pretty much be negated by the service foot hes pushing.

I still think he should shift the paradigm by challenging the bore and stroke of the supposedly 6HP Seahorse friends engine.