I'm running a 21p stainless prop on my 2002 Merc 115 and it just doesn't seem to have the get up and go that my previous prop did. Is this adequate or do I need something new?

If you are on a 17 foot boat and 19 might be in order. What are your max rpms? I owned a 17 foot Ranger with 115 Johnson and ran a 19, it turned about 5400 rpms and adding a 6 inch jack plate and some adjustment brought me 5600 and maybe a couple of more MPH. You might try the prop you have with a jackplate as well. The Ranger was heavy and even with the 19 fully loaded with two tourney fisherman and gear it was almost impossible to get out of the hole. The jack plate made it blow over on the pad like it had another 100 horsepower. Steve @ Steve's Custom Props will catch this in a bit and he will be able to elaborate a little more, maybe a lot more......

I'm running a Tracker Tournament V-18. Not sure about rpm's or where I should be with that prop. This is my first boat so its all fairly new to me as far as the technical stuff

Sounds like it's too much Pitch.

That boat; being aluminum, ought to be launching like it was fired out of gun with that motor. A jack plate on that boat would be kind of ify. I'm not sure how strong the transom is on these boats and if it would holdup to the added torque it would create on the hull so a prop may be your best deal or one of these:
http://www.thmarine.com/products/Outboard-Performance/Hydrofoil-Stabilizers/Hydro-Tail-
I ran one of these on a rig I used to own; a Tracker TX-17, for a while and it seemed to help. The only problem I had with it was the first time I came in contact with a stump I broke it in half.......

Not to mention that once you drill or mount it to the motor cavitation plate; you risk cracking or breaking the cavitation plate when the hydrofoil hits an object.

Proper prop is the best option!

Do yourself a favor and make a phone call Monday to Steve. Tell him the details of your set and your concerns and he will solve your problem.

http://www.stevescustomprops.com/

Oh and one other thing, make sure your livewells are empty and the livewell valves are closed. Only fill them unless you are actually going to put fish in them. Full livewells can take all the punch out of a motor because of the added weight. Water weighs 8-1/3 pounds to the gallon and most livewells will hold around 40 gallons so you are looking at planing and extra 330+ pounds roughly.........your wallet is going to love you for doing this as well when you pull your rig up to the fuel pumps......

John.
take your boat to the lake.
look at the wide open throttle rpms and tell me what it is.
also.. what prop is it?
your engine should be around the 5500 rpms at wot.

now.. that boat being an aluminum boat.. look at the bottom and see if it has alot or any dents!! those dents will kill the performance of your boat!!

Wait guys, that 2+4 merc has a max rpm of 5,200 and it isn't happy running past that, be aware.

Remember it idles on 2 cylinders, runs on 4. The bottom two kick in at 1,800 rpms. If you try to baby it up on plane, you will think it's sick and slow. A properly vented prop will allow it to spool up quicker and let it go ahead and run.

I sold a few of those, and there was a reason we put a small jack plate on it, probably the transom height. I'll recall in a minute.

thanks for the correction Pat. didn't know the exact specs on that mota. good to know.

John since you said you were new to this game I wanted to make sure that you knew that you needed to trim the motor down all the way before taking off, also give the throttle 100% until you break it over. Another thing I need to warn you about is when you put the boat in gear, shift it as fast as you can. Lots of folks including myself have been through this. I thought the gentler I could be with the shifting the better it was for the lower unit gears. I was wrong to the tune of destroying two lower units. If you just ease the shifter forward the gears will bounce of one another a few times until you get it engaged all the way and this will break gear teeth. My mechanic at the time taught me to shift a good quick crisp shift so the gears engage each other as fast as possible minimizing any chance for damage. I move the shift lever as fast as I can and I have has zero issues with lower units since I started doing this years ago.......

I appreciate all of the insight guys. I always take off trimmed all the way down and I know better than to baby it. I have looked at the prop and it must be OEM because there's no brand on it. While driving at lower speeds, say 25 - 30 mph, I feel a tremor in the motor. Possibly due to cavitation? Something to do with my prop? I had my motor rebuilt a few months ago and it never has run quite to my liking since.