Diplomat Props/Jackplates/150hp

[RIturbohonda]

Hello all. So my restoration is in the final stretch! Trailer is overhauled, Chine is re-fiberglassed, interior upholstry and carpet stripped, refiberglassed inside, re-carpeted and the best part, THE WHOLE BOAT has nice fresh new paint! Bucket seats soon to be installed and all the cleats, wires, trimmings and such are going on in the next couple weeks.

SO, it's a mid 90's Diplomat. I'm pretty sure the transom is stiff, i checked it out during the restoration. I KNOW i'm going to be making a manual jackplate for this rig, which will bring the outboard off the transom about 10".

Now here are my broad questions: with a 150hp outboard, and a jackplate, what speeds and handling characteristics will this hull produce? How about with a 175hp or a 200? Is 200hp too much, because the limit that the coastguard warning said was 150.
What pitch prop would you recomend? I've read the cupped props bite better but they're not the "chop" type that like to be halfway out of the water? am i wrong?


I'm big into wakeboarding/tubing/waterskiing as well as going fast. My ideal setup would be as fast as possible, have a huge rooster tail, And tow a tube once in a while.

Thanks for all your help, I will have pictures up in the restoration section as soon as i get most of the little odds and ends tied up, and the racing bucket seats and vinyl work done. By this weekend or the following!
~Even though boating season is coming to an end, I still would love to finish this project up and make it a garage queen for some eye candy to get me through the winter! :cheers

 

[daren34]

i don't think you will need more than 6 inches of j/p an a diplomate
i had a v-4 140 that would run 60 with a 6 inch hydraulic cmc

most v-6's are heavier than the v-4

the transom will hold a 200 if it is still solid

look around on the board same boat as sportfire

chopper props are great for top end but slip like crazy taking off

large round ear cupped props are good for low end pulling quick planing

small pointed ear or raked props generate lots of bow lift

a laser II is probably the best all around for small checkmates

alot depends on what engine you go with

a merc 2.0 150 (xrII) is as light as a v-4 140 johnson not as good on bottom end
as the larger v-6's

if you wan't to ski and go fast go with a hydraulic j/p.
no sence having to replace a manual later

to much set back and you won't be able to keep the bow down
and it will porpose at low speeds
too heavy a motor to far back will couse the same condition
a 200 would probably have to bolt direct to the transom

good luck daren

 

[Mark]

The last year for the Diplomat was 1990. The early 80's version was rated for 150 hp, the rest at 140 hp. The reason was they changed how the rate the motors from crankshaft to propshaft in mid 80's.
Daren has got it about right. 6" setback with a V4, less if possible with a V6. Too much and it is going to porpoise at lower speeds. The 135 to 200 Mercs all weigh the same. The prop pitch will really all depend on your horsepower and your setup. I have a 130 V4 Yamaha on 6" setback on mine. I can turn up to 22" prop but I usually run 19's for holeshot and rev over 6000 for my top end. It goes back to what Daren said...too much prop equals no holeshot on a V4.
Lasers, Yamaha Pro or Powertech PTR3 all work well on this hull. Next year I have 2 four blades to try, an RXB4 and PTR4...but alas the boat is already up for the winter.

 

[RIturbohonda]

The last year for the Diplomat was 1990. The early 80's version was rated for 150 hp, the rest at 140 hp. The reason was they changed how the rate the motors from crankshaft to propshaft in mid 80's.
Daren has got it about right. 6" setback with a V4, less if possible with a V6. Too much and it is going to porpoise at lower speeds. The 135 to 200 Mercs all weigh the same. The prop pitch will really all depend on your horsepower and your setup. I have a 130 V4 Yamaha on 6" setback on mine. I can turn up to 22" prop but I usually run 19's for holeshot and rev over 6000 for my top end. It goes back to what Daren said...too much prop equals no holeshot on a V4.
Lasers, Yamaha Pro or Powertech PTR3 all work well on this hull. Next year I have 2 four blades to try, an RXB4 and PTR4...but alas the boat is already up for the winter.

So if i have a higher HP, can i run a better hole shot and only have speed with upper RPM's?

 

[Mark]

I'm not sure I am understanding your question. But, propping a motor is always a bit of a trade off. If you are searching for top speed you prop a little steeper. In doing so you will give up some holeshot. I like a good holeshot for skiing so I am willing to give up some top end. If you opt for a V6 you might find you get a better holeshot with a 150 than a 200 because you will put a steeper prop on the 200. The extra 50 horses are almost all at the top end. Low end grunt...about the same. So every boat/motor combination has it's own set of propping considerations. It all depends what you are looking for.

 

[illMATTic]

here are my 2 cents. maybe 3.

v6 w/jackplate = top end only <60 mph

v4 w/jackplate = both top and low end 60< mph

v4/v6 on transom = better low end only

with my setup (2.4 v6 w/jackplate) i can not run below 30 mph. i start to bounce. I'm fine with that since i do not tube or ski.

if you want to go faster than 60 and also tube and ski, you should run a v6 150 on the transom. you could see 65 witha big prop. you could then prop down to tube.

if you want to run very well at 65 and have a bit of trouble tubing, run a 150 on a jackplate. it will want to porpoise on take off.


i feel you have to choose what you want to do more. speed or ski. if you try to do both, each one will suffer a bit. IMHO