Stock 89 311 Prop question
 

Hi everyone, Just got a 1989 Formula SR1 311 at the end of last season. It has twin 420's with under 200hrs on them and TRS drives. I only had it out two times last year and was not trying to see how fast it would go because I was just getting to know the boat and had 5 plus people in it with a full tank of fuel both times. It has 4 blade 24" pitch bravo props on it right now and from what I've been reading this seams like a little bit to aggressive of a prop selection for the boat and motors. The motors are stock and from what I've read a 23" pitch 3 blade prop is what I should be running or a set of 22" 4 blades.. I could be very far off as I do not know to much about this stuff yet. The boat came out of the hole extremely well and would plane at a low speed very well. Like I said before I did not try to max it out by holding it wide open for a long run and trimming it out but I did open it up a couple times quickly and It seamed very slow midrange and top end. If I recall correctly I think the RPM was around 4500.. may have been lower but I do not think it was any higher. I do know that to get the peak speeds you need to get the boat trimmed out just right but It just seamed like it would never get there. The Speedo was not working then but on a gps I think the fastest seen was 50 ish mph maybe 55. I was also wondering if I could repitch my current props to 22" or if I should be looking for 3 blades? Thanks In advance for any of your input. Just trying to get a head start on this thing before the warm weather hits up here in Canada.

Thanks.

Welcome to the forum and congrats on the Formula.
The three blade will give less bite so planing and low end will not be as good, however, with less prop drag the top end is better. The four blade will have more drag so top end is sacrificed a tad bit but planing and mid range are optimized. That is a little perspective as far as blade count. On the part of what should be on the boat well that also depends on some variables. Are the motors completely healthy? The loads and water conditions will also play into it.
My 357 is stroked 420's at 500HP each with TRS and propped with 24 Bravos. Your 311 mono hull is shorter, lighter and wetted length in the water is less so maybe this package could turn 24's with healthy engines but I don't know what that boat came with. Some others here with 311's TRS can speak to how the original was propped.

Thanks aquaforce. The motors should be healthy.. They only have about 170-180 hours on them and they seem to run well. I wouldn't mind sacrificing some out of the hole to gain up top. I would love to hear from anyone with a 311 and stock 420's to see what they suggest. Thanks again aquaforce.

PM Perfect Storm

Boat would have come with 3 blade mirage 23s. Those or mirage plus 23 would probably be the best for that boat.

Ok thanks, I think I will start looking for a set of mirage 23's unless told otherwise. Does anyone have a set for sale? would it be easy to find someone looking to buy my bravo 24's?

Thanks again.

Tyler, how much would you want for your Bravo 24's. Also, I'm in Omaha, NE.

I'd like to trade for a set of mirage 23'S . If I can't find that I would just like to get what it will cost me to buy used mirages.

Post pics of the boat! We all love pics of new family members boats!

I have a set of 23P Mirage Reconed & changed to Mirage Plus last year by BBlades never seen water since I got them back.. PM me you email & I'll send you pics.

Tyler, I have a set of Mirage 23's that I'd be willing to trade. They are the stock propellers that my 91 311 came with. Let me know.

When my bravo 311 had 454 mags with single planes, hp500 carbs, dui ignitions and emi thunder exhaust turned 24p b1's to 5000 loaded, could turn 5200 light on fuel.