Propeller question, Any help would be greatly appreciated

With spring just around the corner (well, my next Florida trip is anyway), it's almost time for me to do some upgrades on my water buggy. Since I had to change my outboard last season due to an exploded cylinder, it's been running great now. But I'm still experiencing a sluggish hole shot, just like I did with the smaller outboard.
The hole shot is much better right now (about 10-15 feet), but only if I am alone in the boat or the live wells are empty. Add the weight of another adult or the water in the live wells, it takes over 100 yards to get on plane. Not a pleasant experience plowing the water for that long.
I've talked to my mechanic and told him that I had tried a vented prop with no success. He suggested a 4-blade aluminum prop in the same pitch (current is a 3-blade aluminum) for the increase in lift.
If someone knows of a place where I may get a quality used 17-pitch 4-blade aluminum prop, I surely would like to know.

Go with a stainless prop. The aluminum prop flexes to much. Have you looked into where your motor is bolted to the boat, maybe it needs to be lowered? How big is the boat and motor?

It's a 115hp Merc Optimax mounted on a manual jack plate to my 17' Procraft bass boat. The jack plate is in it's lowest position right now. When I had my outboard replaced last summer, they drove it around to check it out, pulled it out and changed the prop plus lowered the motor, and ran it again before letting me have it again.

Something doesn't sound right. You should have much better performance than that. I once had a 115 Johnson on a 19 foot fibreglass Searay, a much heavier boat. Even with our family of five, plus all our stuff for a weekend at the cottage, it had a decent hole shot. A little more info might help: Assuming you have power trim have you tried changing it. The optimum trim for hole shot is lower than for top speed once up on the plane. Once up on plane what is your speed and how does the WOT RPM compare to the max spec for that motor and is the cavitation plate running at the right depth for that motor? The optimum pitch for hole shot is lower than for top speed, you may need to go down in pitch. As far as four bladed or stainless props go, they do offer some advantages but IMO neither are the complete answer to your issue. Forgive the long ramble, just my nickel, the penny is obsolete. YMMV.

When starting out at idle, the trim is adjusted fully down and isn't adjusted until I'm on plane. My RPM's during the hole shot is around 4K, max RPM's is 5600. But with the second passenger and gear plus the live wells full, my hole shot struggles to get to 3500rpm. Only once did I try getting the passenger to sit further forward on the casting deck until getting on plane and that helped.
As I stated in the first post, it generally takes me about 15 feet to get on plane with the higher RPM's when I'm in the boat alone. The prop that was on my 90hp Merc was a 21 pitch stainless. I originally had that installed this one and it struggled, plus the max RPM's was around 5K. I changed it to the 17 pitch that was originally on this replacement outboard when I bought it and performance was greatly improved with the max RPMs up where it's supposed to be (according to my Merc mechanic).
I was told that a stainless prop would be more efficient because of the lessened prop bending and better "bite" over aluminum, but I'm trying to keep my cost down because this is probably going to be my last season having a boat. That's why I was looking at a 4-blade aluminum.
As for the cavitation plate, I have no idea how far below the keel it's sitting in the water, but the motor is fully trimmed down during acceleration.

Putting the passenger up front to improve hole shot usually indicates an underpowered boat, hardly the case here. Amongst other things, it can also mean you have too high a pitch prop. If you can find a place that specializes in props I suggest you seek their advice. If not, I'd suggest you try to get the loan of a standard aluminum @ 15 pitch. That sounds like a very low pitch for sure but stranger things have happened. (It does sounds like the two outboards may have different lower unit gear ratios.) All that said, I'd also want to be sure that the motor really was properly positioned, especially height. Is there a dealer handy that you could consult with? Finally, if you are not keeping the boat for long, the cost of a stainless really can't be justified. In my experience, it's chief advantage for me was the improved fuel economy. And yes, a four bladed can help a little with hole shot but I question if it would be enough for you. Your problem sounds larger than that.
I hope that helps, even a little. Gawd knows I'm no expert, just an old guy who's been around boats all his life.

ThorahGuy, I appreciate your insight. The dealer/maintenance shop that I deal with in Markham is Central Marine on Woodbine. Thus far, they've been fair and very helpful with any issues that I've had with this boat for the past 5 years that I've had it. I chose them on recommendations for location but also because they are a Mercury outlet/dealership. Kim is the one who suggested the 4-blade aluminum prop, even when I had the same problem with the other outboard. Once the water gets soft again, I'll be doing a lot of checking around to try to find a used 4-blade to try, and I'll also have Kim check the positioning of the outboard.
I've had a few people tell me that the 4-blade would help with "lift", but at a sacrifice of top end speed. Believe me, speed is the least of my considerations. My current top end is about 42mph, but my normal cruising speed on a dead flat calm lake is about 32-35mph. I lost my need for speed in the 1970's!

Thank you for the added info, it helps. Since your top speed is well over your desired cruising speed you certainly can afford to trade some of that off for improved hole shot. I'm leaning more than ever to the lower pitch standard prop. It should be much easier to find and probably cheaper than the four blade same pitch. You may have to watch that you don't exceed the maximum rpm for your motor, especially when you are alone in the boat, and it may also result in a small increase in fuel consumption. Good luck.

After reading your previous responses, I was thinking the same thing as well....going to down in pitch to a 15 and being super conscious of the RPM's when alone in the boat or with the live wells empty. Right now, with the hot foot fully pressed down I'm right on the max rated RPM's so I'd just have to get used to backing off once on plane, which I do right now anyway.
Again, thanks for the valuable information.

my quick 2 cents, I struggled with this problem too - I tried a $70 hydro tail on my optimax and it changed my life! I may have got lucky but I shoot out of the hole and plane instantly.

Never used one but if you can get one on trial, it might just be the ticket. Similar affect to trim tabs but a lot less complicated.

I also got mine at Central Marine in Markham but you can get them anywhere - they dont last forever but holy smokes - night and day.....

That is something that Kim brought up as well, but he thought the 4-blade would be more effective than the hydrofoil.

yes Foil! couldn't remember the bloody name! good luck

I had these issues with my legend bass boat with the 60 hp mercury on it.
changed to a 4 blade and it fixed everything. You said you are running a 17 pitch 3 blade right now? and your rpms are at 5600 at wide open throttle?

If so then that prop is the right one for the boat but not for a tournament load.
Try to find a 4 blade 16 pitch propeller, when you go to a 4 blade the diameter might change a little and the pitch must be at least 1 down from the current 3 blade that you are running to get the same overall performance and keep the same top end rpms but with a better holeshot.

for example i am currently re propping my boat:
my current prop is a 14.25dia x 21 pitch 3 blade and the equivalent prop that is in 4 blade that would keep my rpms the same at wide open throttle is a 14dia x 20 pitch 4 blade

You might loose 2-5 mph on the top end, depends on the load of the boat but the holeshot will be worth it.

try canadianpropeller.ca or amazon and ebay if you know exactly what you want to get.