Hello,

We have been working on our 30' S type for sometime now doing a complete rerig, and recently installed some decent power. Current setup is a pair of 516 CID BBC making around 625 HP and 650 tq. We were told by the engine builder to prop them to max out around 5200 RPM. Boat has 72C trannys and TRS drives. Since we needed a starting point with props we started out with a set of 27 P mirage plus three blades.

So far best top speed is 73 MPH on GPS with three of us on the boat and fairly heavy on fuel. While this is a huge improvement from before (and we are running 60 MPH @ 4000 RPM's ) I know there is more on the table here. Motors are only turning around 4800-4900 RPM with the 27's.

What else should I be looking at here, I know prop is probably the biggest issue, but what about drive alignment or anything else? Props are currently spinning in which I am led to believe will produce a better top end.

What props seem to work best with the TRS? I was told to shy away from a 4 blade because it loads the drives more, but if the 4 blade is the answer we will try it.

Any help would be greatly appreciated.

Thanks

Brad Harbold

I would try some 25mirage's. TRS's run better with 3 blades most of the time. And is there a dyno sheet for the engines? You should be able to pull the 27's with that HP.

Brad, I got your Email and your boat must have a low X dimension to only be running at 73 mph.Ernie's boat ran 86 mph with these engines at 5200 rpm's with the 27 Mirage plus's he sold you but his boat is a Bravo boat with a higher X with prop shafts at 4.75" below transom. I would try a set of 25 Mirage plus's and get the rpm's up to 5200-5300. As far as the condensation in the valve covers, some of that would of been from dyno time and should clear up with a long run. Do you have oil temp gauges? If so what temps are you running? Should be around 230 degrees to remove the moisture. Please do not play with the jetting.......yes it is on the safe side but with todays fuels it is not worth the extra 10-20 HP to take a chance on melt down.
Keep us posted and have fun it looks like you are headed in the right direction. Brian

stupid question but I assume you put a performance exhaust on the engines? If the cam is to big even on performance exhaust can cause reversion and suck water back in the engine causing moisture. trs have a very low x dimension i would not recommend 4 blades.

Yes the boat has stainless marine exhaust with pipes dry all the way to the tips. We saw 75 MPH today in a little more chop. As for the oil temps we dont even get to 190 after a long hard run. I know they need to be higher to burn the water out of the oil, but it just seems strange that the one motor is doing it so much more than the other. We have about 10 hours on them now so were going to drop the oil out and see what it looks like.

I definetly want to play with props, I think there is more in there, we had 5 people on the boat today and no difference in top speed. The power is definetly there. I would love to try a set of 25 or 26 p props to see what it does.

Thanks

Brad