Performance Improvements possible with newer 4 stroke outboards

[Powerabout]

I just noticed on the TORC......Toronto Outboard Race Club..site that the link to the rule book is a link to the 2019 UIM Rule Book....T Class starts on page 194. There is no change in the T750 weight. The GT classes for the New motors are much heavier and are horsepower based not displacement based as the two stroke classes. Our new composite Critchfields weigh 225 lbs without the cowl, we will see the new 2019 redesign Deltas this race season and they could be lighter and quicker than the Critchfield or Allison. One reason OPBAR is looking at reducing the horsepower in T850 is the boats are having turning problems in the corners due to the increased top end speeds on the straights.
They may want to go back to the original spec rules and eliminate the altered 56 fishing motor. Under the original rules you could run a UIM spec 49 OMC or 70CES, an APBA spec 59 cubic inch Mercury, an APBA spec SST 60 with the larger cc 160 compression head or a blueprinted stock 56 fishing motor with the 160 compression head. All of these motors were competitive, some had better acceleration while the OMC 49 and SST 60 had a bit more top end. Made for multiple winners and super racing for the fans.
Simple solution for the OMC 56’s......must run 31.5 cc head regardless of resulting compression and 73D maximum jet size.. That will slow down the altered motors and is easy to check at inspection.

propshaft height is another way to slow boats down and helps safety re spins

[Hounddog]

propshaft height is another way to slow boats down and helps safety re spins

We currently have a prop shaft UIM rule.....basically it must be below the bottom of the boat and we allow nose cones but not low water pick up nose cones or remote transom water pick-ups. We put the nose cone rule in because many T boat owners up here ran SST 60 lower units. At first in 2006 we thought the SST 60 lower units would be an advantage over the nitro case. This was race proven to be false, the nitro case is the faster case on a T boat. The Yamaha small case is even better and the Mercury case even better provided the carrier did not come out. APBA VP75 run the large case with the prop shaft 5 inches?? below the boat plus a much heavier minimum weight. That class has really grown and has many good looking expensive boats racing....and it is much slower compared to our T classes. A few years a go we ran a short shaft big foot 49 with the 725 lb T850 minimum weight in T750. The actual boat and driver used was well over 850 lbs. The boat was a top 3 runner back then. We dropped the idea after one season because it was obvious that had the boat been close to the 725 lb weight, it would dominate.
Maybe??? When T850 is reviewed for 2020 we could revisit this idea with a minimum weight at 850 lbs.

[Powerabout]

We currently have a prop shaft UIM rule.....basically it must be below the bottom of the boat and we allow nose cones but not low water pick up nose cones or remote transom water pick-ups. We put the nose cone rule in because many T boat owners up here ran SST 60 lower units. At first in 2006 we thought the SST 60 lower units would be an advantage over the nitro case. This was race proven to be false, the nitro case is the faster case on a T boat. The Yamaha small case is even better and the Mercury case even better provided the carrier did not come out. APBA VP75 run the large case with the prop shaft 5 inches?? below the boat plus a much heavier minimum weight. That class has really grown and has many good looking expensive boats racing....and it is much slower compared to our T classes. A few years a go we ran a short shaft big foot 49 with the 725 lb T850 minimum weight in T750. The actual boat and driver used was well over 850 lbs. The boat was a top 3 runner back then. We dropped the idea after one season because it was obvious that had the boat been close to the 725 lb weight, it would dominate.
Maybe??? When T850 is reviewed for 2020 we could revisit this idea with a minimum weight at 850 lbs.

Wow, large gearcase with propshaft just under and very low ratio was fast??
What caused that do you think, more diameter with low ratio would get you out of the corners I guess?
How many seconds in a lap for your typical course?
Would make a cheap class i thought, big case on a 15" with stock 49er

[Hounddog]

Wow, large gearcase with propshaft just under and very low ratio was fast??
What caused that do you think, more diameter with low ratio would get you out of the corners I guess?
How many seconds in a lap for your typical course?
Would make a cheap class i thought, big case on a 15" with stock 49er

We tried the 49-big foot-15 inch for several reasons. One was to compare the performance to the VP75 class which only allows long shaft motors. We had tried the long shaft version with a Checkmate a few years prior. T racers did not like the way the long shafts handle. The FE Class prior to 1975 ran big foot short shafts, so we were following that model. The test boat ran 57 to 58 mph with a 12.5 x 24 omc prop. Our course is approximately 1 mile at most sites....top T750 boats about 67 seconds....top T850 boats under 60 seconds. There is a big difference in lap times after lap 3....when we had 9 boats in a heat the water is rough! More prop diameter helps out of the turns in rough water. Another option we have tried on a lake runner is running the higher ratio 2 cylinder nitro on a 49. Works well and is less than half the cost a 3 cylinder nitro. I personally like this option better than the big foot.....same lower cost, but boat handles better and is 3 to 4 mph faster...low 60’s.

[Powerabout]

We tried the 49-big foot-15 inch for several reasons. One was to compare the performance to the VP75 class which only allows long shaft motors. We had tried the long shaft version with a Checkmate a few years prior. T racers did not like the way the long shafts handle. The FE Class prior to 1975 ran big foot short shafts, so we were following that model. The test boat ran 57 to 58 mph with a 12.5 x 24 omc prop. Our course is approximately 1 mile at most sites....top T750 boats about 67 seconds....top T850 boats under 60 seconds. There is a big difference in lap times after lap 3....when we had 9 boats in a heat the water is rough! More prop diameter helps out of the turns in rough water. Another option we have tried on a lake runner is running the higher ratio 2 cylinder nitro on a 49. Works well and is less than half the cost a 3 cylinder nitro. I personally like this option better than the big foot.....same lower cost, but boat handles better and is 3 to 4 mph faster...low 60’s.

thanks Hounddog
sounds like there are lots of options and sustainable/easy to find parts
I thought about a new mid for the 56 so it bolts up, 15" and solid mounts, go racing ( cut drive shaft)

[Hounddog]

thanks Hounddog
sounds like there are lots of options and sustainable/easy to find parts
I thought about a new mid for the 56 so it bolts up, 15" and solid mounts, go racing ( cut drive shaft)

Here in Ontario, Canada we have a shorter boating season and all fresh water so motors last longer and are in better condition compared to most areas. The 75 cent Canadian Dollar hurts when buying from the USA. With the above in mind I think a Hobby T Class would grow once we got a few boats racing. We need to take advantage of the good low cost motors available here and keep the spec rules simple and easy to understand.
HOBBY T CLASS
- V hull
- 850 lb minimum weight
- bone stock 3 cylinder 60 cubic inch maximum ..no custom parts!..Stock head and stock compression!
- no blueprinting
- MOTORS..choice of long or short shaft model
- OMC 49 small carb...choice of big or small lower unit
- Yamaha 52 no CES parts...choice of big or small lower unit
- Mercury 49, 52 or 59 bone stock
Should be a 55 to 62 mph class.
Current Other T rules would apply.

[Powerabout]

Here in Ontario, Canada we have a shorter boating season and all fresh water so motors last longer and are in better condition compared to most areas. The 75 cent Canadian Dollar hurts when buying from the USA. With the above in mind I think a Hobby T Class would grow once we got a few boats racing. We need to take advantage of the good low cost motors available here and keep the spec rules simple and easy to understand.
HOBBY T CLASS
- V hull
- 850 lb minimum weight
- bone stock 3 cylinder 60 cubic inch maximum ..no custom parts!..Stock head and stock compression!
- no blueprinting
- MOTORS..choice of long or short shaft model
- OMC 49 small carb...choice of big or small lower unit
- Yamaha 52 no CES parts...choice of big or small lower unit
- Mercury 49, 52 or 59 bone stock
Should be a 55 to 62 mph class.
Current Other T rules would apply.

solid mounts?
I have watched a few videos of that long shaft stock class and its a bit dodgy