Transom question

[Sonny]

Why are pro transom angles so different than a stocker? If pro transoms are built at a steeper angle to get the gearfoot closer to the back of the boat or planeing surface what can be expected from this? I at one point thought that the gearfoot location was something to do with helping a motor that made lots of rpm and not much torque out of the corner? could this be true? and How?

[Tim Weber]

I'm guessing your talking about hydros?

I am not 100% sure but me thinks a lot has to do with the fact that transoms are 8"-10" in height.

On the runabouts, the angles from what I have seen are not too much different from a stock. I think most of them are about 22 degrees. I know this is what Desilva usually uses on his new stuff.

Tim

[DeanFHobart]

Transom

Pro set-ups have a specific distance they like the propeller to be from the back edge of the bottom. They will usually have the shear pin hole a specific distance from the back edge of the bottom. They can use brackets or transom angle to achieve this.

[bh/]

All boats, props, and drivers are different, and will use slightly different set-ups, but what Tim and Dean have said is if we all agreed that the sweet spot for all props were to be say 12" aft of the boat bottom, and the prop shaft level, and the depth 0", then the transom angle would need to vary depending on mid section height to achieve this set back. PROS will run mids as low as 4", stocks as high as 15".
The short mid section will require a much greater angle than the tall mid to achieve to same set back, all other factors bering equal. But a walk through the pits will tell you that no one will agree on exactly the same set up, set-back, prop, or angle. This is what makes it fun

[Dave M]

Height vs Angle

It matters not what the angle of your transom is, what matters is where the prop is located. A general measurment is from the actual rear of the bottom (not the inset if any) to the center of the shear pin hole. I am sure most serious racers would argue what the best distance is. I have my ideas, others have theire own. Bottom line, test it. With the Pro tower housings, it is much easier to change this distance, a simple block of wood would work if needed. For the Mod's and stocks, it becomes more difficult as most of us use clamp on brackets. Changing the transom can be difficult and ruin a good paint job.

[Sonny]

That makes a lot of sence. Thank you guys. I'm putting together a few boats for this years race season and one of the rigs I'm working on is a DeSilva pro runabout that just so happens to be a perfect B mod boat. I have several Goller midsections, and a few yamato pro midsections and adapters for the y80. Being as that it is a pro boat with a pro transom I am probably best off with the pro tower housing. Thanks again guys

[Dave M]

Cool

Sonny,

Have fun with the project. Sounds like a good ride. BMR is getting more popular here in Region 6, several at most of the local races IOA puts on.

I also would use the pro tower for your set up. If you want any tips on location send me a PM.

[T Chance]

On my Pro motors I use a konig yoke and mounting bar. On the boat I use a Konig thrust socket and DeSilva brackets. Depending on the location of the holes in the brackets determines the set-back of the engine. It works out ok.

There are other systems that allow simpler fine tuning though.

And, this has nothing to do with boat racing but I am so glad that the 24 hours of Daytona is tomorrow because it means the 2009 racing season has started. I went and watched once and it was great and I'm going to go again some day. The Daytona Prototypes are awesome!