Omc 3 cylinder comparison

[Smokin' Joe]

I'm thinking of fishing gearcase vs Nitro or Nitro vs quickie.

In theory maybe, but a 1:1 Mark 20-H compared to a 13:19 20-H, Big prop goes faster than the 1:1 and out accelerated it also. In the PRO Division we never ran 1:1 and the 15:16 was quicker and just as fast. A big prop turning slow moves a lot more water. On our COR Boats the 2:1 is quicker than the 1;86 and close to the same top speed, but around the short course, the 2:1 is best....

You are telling me a 10 X 20 will be better on a Sport C that an 11 X 18??? Or a 9 X 22 would be better yet?

[Hounddog]

We have been running both the 49's and the 56's in T class [V bottom EP style Critchfields] here for several years. Stock to stock a 49 stinger is faster. In a LeMans start the 56 is off the dock faster, but the 49 will run it down, We revised our rules to increase the performance of the 56 because they are newer motors and there are more of them. The rule was simple. You can run 160 compression head on that motor. That increases the compression from 120 to 160. Basically we allow you to put an SST 60 head on a fishing motor. That change makes the two motors competitive.
The 56 now has the extra top end to run with the stinger. It can be even better because it does have more punch out of the turns. All our motors are 15 inch nitro or SST 60 gearcase. They run 66 to 70 mph on the oval.

[phillnjack]

now when you say stock you mean straight from normal everyday marine shop with no mods at all!!!!!!!!!!
or are we talking some mods ?
because i cannot see omc re-tooling costing absolute fortune just to make a slower engine.
the fastest of any outboard and winning means more sales to the public with boat engines.
now i thought the johnson stinger was 75hp at the flywheel, and todays engines rated at prop.
this would make a stinger around 65hp if your lucky.
No way were the stingers faster top end then a mercury 70hp in the uk.dont know about usa, but the stingers over here were slow compared to mercury 3 cylinder.
all the orange stingers ive ever come across were just used for ski-ing as they were slower than normal engines
but good for ski-ing
The stingers were promoted in the uk to be good for water ski-ing,never seen anything about them being fast top end.
it sounds like a lot of engines in the states are totaly different to what we get over here.
mercury dominated the uk for a long time with the 3 cylinder engines.

strange that you say they will be equal or even faster than the 56ci motors.

what happened to make the 56ci so much less power ?


phill

[Powerabout]

so what the 56ci needs is some mods not quite to sst60 spec so it retains its bottom end but a bit more up top
chamfered exhaust ports like a 75?
But if you want close racing sounds like Hounddog has got a solution

[phillnjack]

maybe the orange things with 75 stinger on them over here in uk were all just crap and sold as a gimmic.
coz they sure were not fast compared to most others around.

now the sst 60 i have no idea about, never seen one in the flesh.
I take it these are proper engines similar to motorcycles that push out over double what outboards do for
the same cubic capacity.


phill

[88workcar]

My 13 Allison (1972) is being restored as I get time, transom, core, the whole shabang. I have a question;

I have an old (1980 ish) 75 OMC, not a nitro-cased motor and it has always been preached to me that it would be best to have a nitro motor, due to the 15 inch mid, as well as, narrower gear case. It is also my understanding that the later 56 inch race motor, is even better, but my question is; if I cannot readily purchase an old nitro motor, or a later racing 56 incher, wouldn't the standard later 56 inch, 70hp motor be better than what I have, and as far as top end goes, wouldn't it also be better than the 49 inch nitro motor, simply because it puts out so much more power?

I am cost consious and not doing any sanctioned racing, but like to go fast. It simply seems that their is no good reason for me to spend $2,000 on a good nitro 49 incher, if i can pretty easily spend, $800 on a good, late 1980's 70hp that is "faster" still, though it will lack the 15 inch, on top end, I see this making little difference.

Thoughts please?

If you are not partial to the OMC, I know you have one to start with.... Sell it a go with a 90 Yamaha, great power, great prop selection. And no it is not too big or too heavy. If you think so, what about a 70 Yamaha? On either engine a short shaft is easily attanable and so is a small foot lower unit. On either you can use a 40 lower unit. The parts are still very available and you will have a current style engine. The 70 can quite easly see 8400 rpm and the 90 can quite easly see 7800. In either case, more power than you will fight to get with the omc. ( That statement will start a fire for sure) Just some thoughts for you to kick around, don't limit your self on motor options.

[ima75man]

u right, u starting a fire.lol my 60 h/p omc is faster than my 90 yamaha.. just ask donnie or the bama boyz..

[phillnjack]

was that a joke about the yamaha 70 and 90 engines ?




phill

[Hounddog]

Here you go. Just a stock 56 motor no mods other and using a 28.5 CC SST 60 head. Powerhead cost including the head $700.00 to $800.00.
http://www.youtube.com/watch?v=NaYLot_1XBY&feature=plcp

[Powerabout]

maybe the orange things with 75 stinger on them over here in uk were all just crap and sold as a gimmic.
coz they sure were not fast compared to most others around.

now the sst 60 i have no idea about, never seen one in the flesh.
I take it these are proper engines similar to motorcycles that push out over double what outboards do for
the same cubic capacity.


phill

The 75 would be the last engine I put on a ski boat due to the tall gear ratio and small prop.

There is a reason that bikes can make more horsepower than a boat engine for a few very simple reasons
they have gears
therefore can make use of long expansion chamber
are not required to produce full power at full load sustained
therefore can have power valves on the exhaust which will not last at sustained full load

( just ask a BRP 2 stroke engineer as they make engines for all uses)
PS 3 cylinder Mercs were never in the race as a racing compeditor to the OMC 3 cylinder and I guess 20 years of results proves that
The OMC 3 cyl was the only OMC that my mates at Mercury would concede was a good engine - because they couldnt beat it clearly