Hey all! I've been staring at propeller numbers for a while now and thought I'd see if I can get some input from some more experienced minds here. I've recently bought my first boat, a 1993 Baja Islander 240 with a stock Merc 7.4L (non Mag, about 650 hours) and Bravo 1 Outdrive. I've only had one successful trip thus far where I got to really open it up, so I don't have a ton of data, but this is what I'm looking at. Last trip it was 2 people on board and a full tank (60 gallons) of fuel. Holeshot is pretty comfortable, I had GREAT success popping out of the water super easily with a little steering to rock the hull. Even without that, holeshot was pretty decent. For speed, farthest I pushed it was about 5200rpm, which got me right about 50 mph. IF I'd stayed on it, I think it had a bit more to go, too. Now, a few problems I have with this:
Pretty dang uncomfortable with the motor turning over 5k. General consensus I've found is that the 4200-4600 WOT Mercruiser specifies may be a tad conservative, but pushing 5k is really rolling the dice on stock internals. I'd probably be happy if I was at 4700-4800 WOT with a light load in the boat, as it'll usually have a few more people on board.
My numbers put into a prop slip calculator show slip at over 27%. This seems like its pretty darn wrong. This is with GPS speedo, and the tach gauge on the dash, NOT a timing light.
This is all on a 3 blade SS Stiletto Advantage II 14.25x21P prop. Thinking of looking for a 4 blade 23P, hoping that it will keep a decent holeshot thanks to the extra blade, and steeper pitch maintaining top end speed at lower RPM? And I'd suspect the extra blade would help with prop slip? I'm not trying to race anybody, more comfortable cruising around 40 than going balls out all day long. Just looking to make sure the motor lasts, only wanting to keep this boat 2-3 years. I'm happy with the current performance of the boat, but want to make sure it doesn't over-rev without losing the holeshot too terribly bad.
Any thoughts from those wiser than me would be greatly appreciated! Thanks!
Pretty dang uncomfortable with the motor turning over 5k. General consensus I've found is that the 4200-4600 WOT Mercruiser specifies may be a tad conservative, but pushing 5k is really rolling the dice on stock internals. I'd probably be happy if I was at 4700-4800 WOT with a light load in the boat, as it'll usually have a few more people on board.
My numbers put into a prop slip calculator show slip at over 27%. This seems like its pretty darn wrong. This is with GPS speedo, and the tach gauge on the dash, NOT a timing light.
This is all on a 3 blade SS Stiletto Advantage II 14.25x21P prop. Thinking of looking for a 4 blade 23P, hoping that it will keep a decent holeshot thanks to the extra blade, and steeper pitch maintaining top end speed at lower RPM? And I'd suspect the extra blade would help with prop slip? I'm not trying to race anybody, more comfortable cruising around 40 than going balls out all day long. Just looking to make sure the motor lasts, only wanting to keep this boat 2-3 years. I'm happy with the current performance of the boat, but want to make sure it doesn't over-rev without losing the holeshot too terribly bad.
Any thoughts from those wiser than me would be greatly appreciated! Thanks!
