Another prop question

[85Predictor]

Ran my Mate yesterday with a GPS on board.
Predictor with 115 Merc.
Speed at 46mph and tach at 5500-5600??
I think the prop is a 19P. Can I go to a 20P, reduce the rpm to say 5000-5100, and still have power out of the hole? (Skiing)

-Thanks-

[85Predictor]

Ran my Mate yesterday with a GPS on board.
Predictor with 115 Merc.
Speed at 46mph and tach at 5500-5600??
I think the prop is a 19P. Can I go to a 20P, reduce the rpm to say 5000-5100, and still have power out of the hole? (Skiing)

-Thanks-

[Bill]

You want to run your rpm's at the maximum recommended by Merc. Any less, you are putting stess on the motor by causing it to work too hard. I do not remember if you had a jackplate or not. If not, get one along with a water pressure guage and you will see a HUGE improvement. I used to have a 1985 Diplomat that origonally came with a 115 Johnson. I relaced it with a 120 Evinrude, put a jackplate on, blue printed the bottom, and the best speed I got with a 24p Raker at 6000 rpm was a hair under 70 on gps and light fuel with no passengers. With one other person, full fuel and full beer, I could run 63 all day long. Good luck!

2003 ZT 240 6.2litre/Bravo 320 H.P. 24p Bravo 1

[Bill]

I forgotm with the 115 and no jackplate, all I could run was 49!

2003 ZT 240 6.2litre/Bravo 320 H.P. 24p Bravo 1

[85Predictor]

Bill,
How will the "Full Beer" work into the equation?
I do not have a jackplate and probably will not get one. I guess I would have to test drive a prop to see what would happen to the rpm and speed.
How long is too long keeping the engine at max rpm??
My Merc is a 1987 and the book states 5000 to 5500 rpm. It is not real new and do not want to over-rev it.
-Thanks-

[175checkmate]

A jackplate makes a world of differance. I had a hyd. plate on mine last year. With the plate all the way down I could run about 51 mph. With the plate all the way up I got 68 with 2 people. Still had great handling and holeshot. I was amazed at the amount of differance.

http://www.checkmate-boats.com/6/ws/,s,8626072361/avatars/rooster_3.jpg


1975 Checkmate Tri-mate 2, 2.4 200+ / Sky jacker 6" plate / 25p Laser 2 prop

[Bill]

85Predictor,

"full beer" with a cooler and ice equates to about 75lbs. Of course, as the day goes by, that will decrease! http://www.checkmate-boats.com/infopop/emoticons/icon_wink.gif http://www.checkmate-boats.com/6/ws/,s,8626072361/Graemlins/thumb.gif

If you really need more spped, I highly recommend a Manuel Jack plate. You can pick those up for 200 bucks or less and a water pressure guage for less than 50 bucks. They are both very easy to install, and like Gus said, well worth it.

2003 ZT 240 6.2litre/Bravo 320 H.P. 24p Bravo 1

[175checkmate]

Overtons hasa a 6" setback jackplate for $139
Cheap for the speed gained.

http://www.checkmate-boats.com/6/ws/,s,8626072361/avatars/rooster_3.jpg


1975 Checkmate Tri-mate 2, 2.4 200+ / Sky jacker 6" plate / 25p Laser 2 prop

[Mark]

Hey 85
My Diplomat with a 115 Merc ran 50mph @5600 with a 19" Ballistic and no jackplate. I gained 5 mph when I switched from a 19" QSS at the same RPM. I'm seeing 60mph with my new Yamaha 130 but I'm going to start my own post to deal with that. The Predictor is 100 pounds lighter and narrower so you should be seeing another 5mph with the right prop. Your pitch is probably right on the money. Predictors/Enticers have a tendency to porpoise so I would want to hear what the experts say a jackplate will do in that regard.
Mark

[175checkmate]

My trimate would porpoise with the plate all the way down. Went away with the plate up. Since my hyd plate was shot I took a base line for the prop height befor I did the ransom. Now with the 6" setback and new plate I am at the same height starting out, but can go heigher if I need to. When I installed the new transom I did away with the dip in the splash well. I was able to mount the engine 3" higher that factory.http://forums.screamandfly.com/forums/attachment.php?s=&postid=209811

http://www.checkmate-boats.com/6/ws/,s,8626072361/avatars/rooster_3.jpg


1975 Checkmate Tri-mate 2, 2.4 200+ / Sky jacker 6" plate / 25p Laser 2 prop