MitchStellin

This is what I have now, if I went to a four blade 28 would I pick up speed, why the current combo, I run around 4800 right now. hp500s and bravo one drives. Is this a good set up for cruising and occasional bursts? I have some questions, thanks

Strip Poker 388

iTrader: (6)

Rpm to low. the hp 500 which is the carb motor . I would turn it 5200-5300 with out any quams.when summer comes in the rpm will drop

dyno

Mitch I think the boat had bigger power at one time thus the 1.36's if you go to a 4 blade I think you would need to go to the 1.50's to keep the r's up. I'd sent the 25's to Darrin at Houston and get them labbed. Better yet you can try my labbed 23's right now...they are just sittin on the bench!!
Don

throttleup

What kind of boat do you have? What year? What kind of speed do you see at 4800 rpm? Which props are they. Lab finishing your current props may not be the right thing to do without looking at all your options. 4 blade props are an option, with the proper pitch they will turn the proper rpm

Strip poker is right. Those Hp 500's will run all day at 5200-5300 and perform their best.

The 1.36 gear set is not the optimum set-up for your current co figuration. If you had the 1.5 gear set your 25's would run the proper rpm.

Matt

Bill272

I've got a 95 Formula 336 with HP500's, 1.36's, and labbed 23" mirages. I've wondered why they did this since it was set up that way from the factory. I do spin them up to 5100-5200 though. I had always thought that 1.50's were used until props got too big to get up on plane.

dyno

Bill it came with the 1.36's???? When does Merc do that?I thought the 500 HP's all had 1.50's......Someone enlighten us.....

Cord

iTrader: (2)

Mitch-when you get the coin, I'd get the drives changed to 1.5's. That's what should be on the boat. You'll have much better mid range. Your drives are pretty deep so I don't know if you'll benefit from the 4 blade. Heck, there is no slippage when planing. You would see a speed increase with a shorter lower. At that time I'd explore the 4 blade bravo option. The rough water manners would be slightly compromised with a shorter lower though.

To answer your question, you will slow down with 28's. That's too much prop for your boat and you'll bog the motors below their torque peak.

For the record, these are not blue motor 500's. They are 502's built to 500 horse power. Maybe Mitch knows what originally powered the boat. I never heard it come up.

The boat is a 94 (?) Active Thunder 32.

formula31

I had 1.36's on my formula 311and they originally came with the HP465's, After serious hp upgrades it was easily a great combo for my engines and boat. others have had different results.

MitchStellin

Yes it is a 1994 Active Thunder 32. The engines are the 502 with the hp500 kit. I saw 4800 or so last night but I don't think it was wide open. This was the first ride by myself and with all the news on crashes I am going to take it slow to top speed, maybe after 5 or 6 runs with the boat, it handled great though with no loose feeling or porposing. The 1:36 gears do make for a fast idle speed, I need to get used to this around the docks. I think I will try these at top RPM, I think he said 4800 right now, and then try the 23s Don has. Thanks, any info is greatly appreciated.

dyno

Test and Tune!!Thats the most fun!!!