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It was very difficult to come up with a simple engine spec sheet for T Class because there were so many different combinations of boats and motors run by people who were interested in racing. The engine maximum displacement spec was easy. Maximum displacement would be 60 cubic inches. That size covered ALL of the motors. I didn’t change the title of the class from T850 to T1000 because of the UIM World Wide recognition for that class.

I needed to make engine spec rules that would equalize the different motors performance so all these combinations would be equal. That was a challenge! The “yardstick “ motor was a 100% legal Yamaha 70CES. That was the most common motor raced in UIM T850 world wide and it held all the speed records for the class. Fortunately the 70CES we had in our group performed almost exactly to the record book T850 class records.

The problem motor was the 56 cubic inch OMC. The fishing version under performed and the SST 60 version over performed the 70CES in actual race and testing. Both the 49 OMC and the 60 cubic inch mercury were very competitive with the 70CES.

I decided to try different volume cylinder heads on the 56 OMC motors to see if I could improve the fishing motors and reduce the SST 60 performance. I was also mindful that I didn’t want to change any spec for the 49 omc, 70CES or the mercury 60 cubic inch. I wanted to keep the class stock and simple.

I lucked out....if you ran a cylinder head that produced 150 psi compression on either motor. Both motors were competitive. And oddly enough both the 49 omc and 70CES had 150 psi.

I presented my suggestion to the group. I explained that for this to work the motors would need to be stock other than the cylinder head. Internal port changes would change the compression.
The group decided they would follow the rule, but, wanted it to be 160 psi not 150 psi.
So that is where the 160 psi rule as added.

I wanted T class to expand and allow newer motors into the class. I also worried one combination would dominate the class and that would reduce the number of entries.
So the last rule was:
The fair competition rule......no boat was allowed to dominate the class.

The racers liked the rule and we never had to enforce it. That rule was removed a few years ago.

Another unique feature of T Class is it races in the Stock Outboard Division of CBF.. Prior classes raced in OPC division of CBF. I needed a title for the that fit the other classes that raced in stock outboard. So the T classes race under VPR. V Production Runabout

In 2024 we had 10 entries in T850 and their races were very competitive and great to watch.
In the past when be had entries in both T750 and T850 the total number of entries was between 15 and 20 per event.

The current T group are working well together in promoting the class. They are encouraging more people to come out and try racing.

Question:
Why are there no 59 cubic inch mercury currently racing in T850?

The reason is the motor is no longer competitive compared to the 56 cubic inch OMC.
The same can be said for the 49 cubic inch OMC and the Yamaha 70CES.
Even 56 cubic inch OMC that were competitive a few years ago are not as competitive now.
Competition in the group has raised the performance level.
The performance level didn’t increase overnight in fact one of the top running boats is running a powerhead that was initially raced in 2014.
So it’s not just the motors being more powerful, it’s better props, better setups, more experienced drivers.

Now would it be possible to build a competitive 59 cubic inch mercury? I don’t think so.
There were a couple that ran in SLT class years ago and they were competitive with the 56 OMC. Those motors were likely built by Jeff Dunn or Hydro Tec. They would have been expensive.

The first problem is finding a 59 mercury or mariner short shaft. Jeff Dunn may or may not still have his high compression pistons. Then you need to build it or have it built. Risky and costly if it’s not built right. If T850 was still a 72 to 75 mph class one of these motors would be very competitive. But, T850 is now a 75 to 78 mph class to be a top runner in the class.

The last 59 mercury to race in T850 was Rusty’s. I believe he raced it one season and then switched to running a 56 OMC.

If your interested in looking into building a 59 mercury you could look at the 40 hp 59 cubic inch model. There are more of the 40 & 50 hp short shaft models around. Sometimes a modified tiller model will show up on marketplace in the southern US. They were run as part of the drag boat group.

They are surprisingly fast!
https://www.youtube.com/watch?v=0JGyku_oYiY

https://www.youtube.com/watch?v=O4qY3O1lHpM

I just checked marketplace here and this appears to be a 59 cubic inch, 40 hp short shaft.
https://www.facebook.com/marketplace/it ... af58e674f4