Looking for some prop help

[BillieS]

I was looking over the engine while we were anchored over the weekend. I noticed that the prop has play in it and may need to be replacing it this fall/spring. I was reading on here about transom adjustment, prop sizes and the like. So, I also took notice that the RPMS seem low on the boat. I know I do not have a speed queen, nor do I want one. But I do want to get the best performace from the boat to engine ratio. If I have to replace the prop I want to get the best performance I can get. Here is what I know and what I know I have:

2008 22' Tracker Fishn Barge
Two adults
Standard tank full
Engine - Mercury 60 HP Bigfoot, 2007/maybe 2008 4 stroke
Speed with no wind, calm water - 18.2 MPH, usually 17.8 MPH average at WOT, this is with GPS
RPM's at WOT - 5200

What Prop should I be running? I do not currently know what pitch it is, as the boat is in the water. I will be pulling it out soon and will take the prop off at that time.

[OK Toon]

Actually, that sounds like about as good as you are going to get. I have a 90hp 4-stroke on my 22' 2-toon and I get about 20mph by GPS at 5000rpm. 5200rpm is about all you'll want at WOT for your 60hp. As far as the play in the prop, you might pull the cotter pin and tighten the prop nut a bit then replace the cotter pin (reusing a cotter pin is not a good idea and they are cheap to replace).

[Tlowry]

Looks like there is only a little room for improvement but not much. You are already near the MAX RPM but you could tweak the prop a little to get it up but the gain in speed will be minimal.

Get your current prop specs and use this calculator to compute slippage then fiddle with the prop numbers to get max RPM then you'll see what speed you will gain.

http://www.go-fast.com/Prop_Slip_Calculator.htm

[jayw]

What prop do you have? What's the diameter & pitch? Assume aluminum and 3 blade.

Isn't WOT for that motor 5500-6000? Once you confirm what WOT throttle is, prop to get as close as you can to top # under your typical load. As you load up people & gear, you'll lose RPMs. I'd go down 2", 3" even 4" in pitch on the prop, I bet you like the boat more. May not be a ton faster but you'll gain a bit, plus have a more responsive throttle.

Try Ken at Prop Gods, he has an exchange pgm for props. Not sure about aluminum though. Overtons and the like won't exchange a prop. Or you could try eBay, people who are repropping resell their mistakes there. I have - not since I found Ken though.

Oh yeah play in the prop - lateral or side to side play is not good. Horizontal mvmt on the prop shaft could be normal. You should confirm it is tight and that the hub looks good. Is it clunking badly? Doesn't mean a new prop though. If it were me I would call a marine mechanic I trust or even call Mercury customer support, they will answer your question about fore and aft prop movement.

Customer service - where Mercury really shines. I love our Suzuki but the CS sucks, they won't even answer questions at all. They refer you to your dealer.

[BillieS]

JayW, I think you are correct that the RPM should be closer to 6K. Lke I said I am not worried about the speed, I just want to get the best performance. How can you get ahold of Ken? Is he here on this forum. I will call them and see what they say. I will have the boat out of the water soon, then I will know he pitch and specs.

[jayw]

JayW, I think you are correct that the RPM should be closer to 6K. Lke I said I am not worried about the speed, I just want to get the best performance. How can you get ahold of Ken? Is he here on this forum. I will call them and see what they say. I will have the boat out of the water soon, then I will know he pitch and specs.

Ken Reeves at Prop Gods in Sarasota FL
propgods.com
Never seen Ken on this forum but he has his own forum on his site.

You can buy and exchange undamaged props, you pay shipping
you can also "rent" test props, $35 a shot plus shipping. For AL I'd call Ken, get his advise, and go with it. He has always been right.
He does not like Merc aluminum props so don't be surprised if he tells you to go with Solas or even Turning Point

If you are near a sandbar jump out and try to read the stamp on the prop. Shut the engine off and tilt the motor out of the water. it's a newer boat so the prop is probably a newer Merc prop I would guess with a stamp of DIAMETER and PITCH

You don't want to be near the bottom end of the WOT range for your motor, esp. not under light load. You could lug the motor with some extra weight, not a good thing - stresses the engine.

on a motor like yours I would expect 200RPM up for every 1" in prop pitch you drop. IE, going from a 15P prop to a 12P prop should gain you 600 RPMS at the top of the throttle. That's the theory. I'd shoot for 6000RPMs if that's the high end of the WOT range for your boat.

Also mention the play to Ken, he is a great guy and will help you out

[BillieS]

Got the site. Thanks! The play I mentioend is horizonal play, not side to side. So it may be pinion gear play. I will know more when I remove it. Thnaks for the help! Lots of information there. It looks like i need to make some height adjustments first. My engine is sunk deep into the water at WOT.