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For the first time Seaway Marine does not have any gear sets for the 3 cylinder OMC nitro case. I am trying to get some of the 49 fellows to part with their gear sets. We also would like to increase our boat count in T class. The T850 class is too fast for the 49's. We tested a Critchfield with a 49, big carb, big foot in T750 a few years ago. With a lighter driver that combo would be too fast for T750. The big gear case was not comfortable to race compared to the nitro.
So here is my idea. The 49 did come stock with smaller carbs, there are lots of the 2 cylinder nitro cases available. To run the 2 cylinder case on the 3 cylinder you only need to change the drive shaft. I think you will need a 25 pitch prop because of the gear ratio. The boat must be T850 weight (725 lbs). The boat should handle well and accelerate very well. It would be low cost and we could see more boats come out and more parts available.

As the pinion end of the drive shaft on the 2 and 3 cylinders are the same a straight swap would be ok. Yes you will need a bigger pitch prop and a fuller diameter of 12 to 12 1/2 in. Pitch would have to be 25 to 27 in but the one to suit would probably be a 26 in pitch. Ron Hill can make a run of 26 in pitches if there was enough interest. Another alternative might be for a gear manufacture to do a 15 tooth pinion that would be able to be matched and meshed to the 29 in gears making it a 15:29 ratio that would then be close to the 15:28 3 cylinder gears.

Stephen

What size bore are the small carbs on a 49'er? Im not really sure which ones im running right now other then they are the primer style vs the butterfly style choke. I may end up doing the 2 cylinder gearcase if i can find one cheap. I could see that making a huge difference to handling, with more seat time i think you could race a big case successfully but it would be questionable compared to a nitro.
Good thought on getting a 15 tooth pinion to match the 29 tooth gear, it would be super close to the 15:28 gears

Hobbing custom gears, grinding and heat treating them in low volume would be very costly. I think the 2 cyl. case is the way to go. We run 12.5" diameter and higher pitch on our T-750 and turn 7350 rpm. Our rig race ready is 760 lbs. with driver. So I know we will need higher pitch props that are hard to find. Yes, Ron Hill would have to make some, 26, & 27's & perhaps 28's. That would be the place to start. If Hill will build the props, then we have a doable package for T-750. I might be one of the first to build a motor for the class, in that Myself, Todd and Matt are heavy weights and could use more cubic inches?

By the way, I think the Oval Port 56.1 cid came thru with the same spline crank as the drive shaft on the 2 cyl. So that crank can work in a 49.7 cid.

[quote="hec2buck"By the way, I think the Oval Port 56.1 cid came thru with the same spline crank as the drive shaft on the 2 cyl. So that crank can work in a 49.7 cid.[/quote]
Wouldn't that be nice! I will find a fine spline crank and see if it fits. A smooth running 49 with a fine spline crank on a 2 cylinder nitro case would be interesting and low cost even if it is only a lake runner. You guys could rework a 26 to work on this combo.

I think that although the driveshaft on the 2 cylinder OMC is fine splined it is smaller than the 70hp 56ci fine splined and will not fit. I have both and will check out and advise.

Stephen

yes different diameters

That narrows to only one option...the drive shaft. The coarse spline short shaft drive shafts are still around....you could cut and weld a coarse or fine spline end on a short or long shaft 2 cylinder drive shaft and there a lots of those parts available. If there is interest, I will get a cost on getting a few made.

I still think you're playing with fire....a 49 omc or Yamaha is an 850 slow or not. It doesn't belong in 750...or 750 will be an 850 class and 850 will be an SST60 class (which it is now anyways).

The problem we have is T850 has become a single motor SST60 class as you say. All the other motors are not competitive and those people lost interest. If T750 follows the normal growth pattern we likely will see 7 boats in the class 3 years from now.
I am ALWAYS trying new ideas to grow the classes. Interest in T850 is dropping. Some of the reasons are.....cost....too fast...parts availability.
So let's say this 100 percent bone stock 49 idea produces a low 60 mph raceboat. The motor is similar to the successful APBA class in the states except it is a much faster and a. better handling boat.
These boats would run in T850 as a separate group along with the 49 Mercury which is in T750 on probation.
I will repeat what I said many times over the last few years. quote: there has never been a mod OPC class last in racing.