More HP or Torque
 

Trying again with a new thread: Formula PC27 single 502 weighing 10000 pounds. Need more of something to get me out of the hole. WOT at 4700 RPM doing 45 MPH 1/2 tank fuel reading with a GPS, normal cruise at 3600 RPM at 32MPH. Put six folks on the boat and other stuff and it has a heck of a time getting on plane, turns 3750 RPM to do 32 MPH. Have a 2:1 bravo 3 drive turning 22 degree pitch props. Do I build/buy a 540 or do change out rectangular port heads for oval port (oval port heads suggested by another offshore member). I'd like to go through the engine this fall and have it ready for spring.

Fixx
 

cheep fixx would be a procharger or a side mount whipple..

option 2 pull the 502 and and sell it, change stringer arrangement and drop a pair of 6.2 mpi's in it and reuse your gimball and drive and add another..

option 3 sell the boat and find a 28ss and save a ton of money on converting your current boat..:drink:

That is a HEAVY boat for a single engine. You can build more motor......but set aside enough $$$ for another drive, you'll be buying one of them soon. Best bet is to drop pitch to get the RPM's up. I'm assuming you have the 502mag (fuel injected) which should have a recommended WOT of 5,000 rpms. Prop the boat to get to that and you'll likely have enough "umph" to get on plane when loaded down.


Actually, you should probably have your props sent out with instructions to tune them to acheive what I described. A good shop should be able to work them and if they have any damage what-so-ever, you shouldn't loose any performance.


BTW: HP makes you go fast, TQ will get you out of the hole.......but TQ is what breaks drives!! (I know, made 700 TQ and busted a couple XR's)

What is the peak rpm on that 502t? 4700 seems low. The cheapest thing you can do is to pitch down in props. Your hole shot will be better with the lower pitch and top speed should be better at optimal rpm (what ever that is...I would think over 5000rpm).

It will be a drive busting mofo if you put any real power to that drive with a 10k boat. I would just have the props labbed or drop down in pitch.

One more thing:drink: you said
"I have a heck of a time getting on plane"
Are you using the trim tabs to help getting on plane?

Ideally you want to be able to spin 5000 under WOT and a normal load. So having your prop set tuned for that is likely the cheapest option. You will probably give up 2-3 mph at cruise, but at least you can get there.

Probably should have mentioned my WOT use to be 4800 RPM but forgot about some of the slime that builds up. I have four sets of props and tried verious things just to get it up quicker, different rakes and cupping. Matter of fact I mis spoke I currently have 24 pitch props on it. When I run 22's it creeps to close to 5000 and I'm turning 3700 to 3800 to stay on plane. When I'm up that high I start getting in to the major fule burn issue. The 3600 RPM range gets me about 1 MPG. With the wife and I it does OK and I know it's not a runabout but I'm looking for what is the best choice. I do have trim tabs and they are all the way down, without them I don't stand a chance of getting up unless by ourself. If I can just figure out the right way to go.

Fixx
 

remove the outter trim ram pin,their should be a white trim insert where the pin slides through,try noving the insert to the rear of the pin hole..this will tuck the drive closer to the transom and hopefully this may help you get on plane quicker..

# 30 http://www.mercruiserparts.com/Show_...nd+Drive+Gears

I'm willing to try anything but a 1/2 inch change on the out end of the drive (maybe .25 degree change) could make that much of an effect on coming out of the hole?