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Yup. That's 714cc. You're fine.

My suggestion would be not to run that model.
http://www.kijiji.ca/v-powerboat-motorb ... nFlag=true

You need to run at least low 50 mph range with acceleration. That model likely runs high 40's at best with poor acceleration.
The T group wanted to get a Mercury motor in the class. That was one reason for allowing the 49 3 cylinder twin carb in.
That motor even though there are 50, 60, 65 and 70 models, there are basically 2 different blocks. The 50 hp and the rest.
The 60 hp prop shaft rated model would be my suggestion. It is allowed in T750 for 2014. Rule changes for 2015 will depend on it's performance in 2014. The motor will not be removed from the class. At worst it would be given a weight penalty to slow it down. We will do the same for any motor that exceeds the class desired displacement. It is part of the classes FAIR COMPETITION RULE.

What will prevent a racer from using the 70hp version of the Mercury 3 cyl. If the blocks are the same, who will know? I assume the port timing is different?

Thanks,

Thom

Thanks for letting me know that the 50 would not be enough. Just have a couple of them. Guess its going be the old 70hp merc. As far as I know my 70 is the same as a 60 .Its that in 1979 my motor was rated at the powerhead and not the prop shaft.
How will gear ratio help these boats. All the mid sections on the 4 cyl and 3 cyl are the same. I have a couple of different bottom ends with different ratio 1.64:1, 1.83:1 and 2:1.

Thom, we need to see how they perform. Same can be said about the current OMCs. How do we know if it is a pure SST 45 or a fishing motor. There are different blocks for it too. The Mercury 60 hp is at the prop shaft. The 65 and 70 I am told is at the crank. There are all kinds of different changes. BUT, they perform the same. If there are rule changes in 2015 then the rules will apply to all of them. The changes will be based on the performance of the BEST one running. Racers runnig this motor would be wise to just run a stock motor.

Good timimg for this post. I hope I answered some of your questions in the post above. The 50 hp 4 cylinder, 35 and 40 2 cylinder and all the 3 cylinder 49's have simlar gear ratios. Like the OMC nitro case there are 2 versions of the gear case shape. The 2 to 1 ratio were on the 2 cylinder and 50 hp. The 1.64 and 1.83 were on the 3 cylinders. One person running a 60 Mercury who has a lot of experience with the motor is switching from the 1.64 to the 1.83 to get more punch out of the turn.

Since we are talking mostly about T750 motors. Here is a list of possible entries.

Number 1 choice is the OMC 60 hp 2 cylinder. IT IS 60 hp at the prop shaft. There are a number of different blocks, mids and gear cases. The motor was produced up into the 2000s. Lots out there to buy and lots of parts available. It has a big advantage because the motor is raced in SST 45 and there is a lot of information on how to get max performance. A spec motor will be over 67 hp.

3 cylinder 43 cubic inch Yamahas and Tohatsu/Nissans. they are 50 hp and very well designed. Costly to buy and not a lot of parts. Tohatsu is the motor of choice in Europe for T750. It has a very wide range of performance because of the large production. I good one can be 59 hp.

2 cylinder Yamahas, Mariners and Tohatsu/Nissans. The models are similar. Some are crank rated others are prop shaft rated. Normally a "C" motor used for commercial applications. They are 55 hp. Very strong built with heavy rotating assemblies. Heavier, but they do have very good mid range power. Rare to find a 15 inch model. There is a 19 inch which is good on a 24 transom VooDoo.

3 cylinder twin carb Mercury. Poorly designed motor. In STOCK form it would not be 60 hp at the prop shaft. On the same boat it performs similar to the PRO 50 Yamaha. Could have a bit more top end, but it does not have the mid range punch.

Green motors...ETEC, EFI models and Mercury 4 stroke.. We don't have any history.

I was under the impression the 2 cylinder omc that most of us run from pre 86 were crank rated and not prop rated. I though the switch over to prop ratings took place in 86-87 depending on the engine and manufacturer.

I'm not sure the OMC is the number one choice based soley on performance, maybe performance and availability of cheap motors/parts.

I want to see one of the 3 cylinder yamahas or tohatsus out on the course I think they will be tough to beat, the exhaust system on them is superior to the two cylinder omc. Maybe one day Dok will build a 50 yamaha to try out.

Don, It was my understanding that the 60 OMC is actually 60hp at the crankshaft? There is no way a 56ci 3cyl is 70hp at the prop and the 45ci 2 cyl 60 is 60hp at the prop!?! There is a huge difference in power between these motors!! (speaking from experience) The newer 60hp motors after 1986 were called 50hp as they were now 50hp at the prop. How about the pro 50 Yamaha? Was it produced after prop shaft ratings came into play? If so, that would put it and any of the later 50hp motors on par with the older 60 OMC's. I would still like to see a pro 50 or 50 Tohatsu run on a good T750 boat.

Lol! Looks like LC and I are on the same page!!