95 SL 750 Tune

[warfare]

If I am running 6340-50 RPMs with a Polaris 5131371 prop. Is this all that I should hope for with a 95 750 with the following mods.
SLX780 stock ride plate
Polaris 5131371 prop Stock 96 SL 900(Skat 15-20 swirl)
Boyseen Pro Reeds
Boyseen Reed Spacers
Ocean Pro Vortex Flame Arrestors
Mikuni 3 outlet high flow fuel pump

[SeaLion]

I'm surprised you are turning that much rpm with that tall impeller. You might be overloading the the engine? How's the bottom end and response? It can't be that great. A 13/18 would be a better choice.

[warfare]

It jumps out of the water. The low and mid seem better than with the stock 4 blade prop. I have a NuJet 5.0 and was wondering what the thoughts would be vs. the 371.

How fast would you guess that would be at 6340 with the 371. I was seeing indicated 53 to 54 and the Yamis I was running with were seeing 58s. Is the 6340 rpms too high for this engine?

[SeaLion]

No you are actually running very well as far as rpm is concerned. I am just surprised that it is with a 15/20 . I guess not all props are created equal I would say 51-52 mph. I had more stuff on my 95 SL750 and ran a 13/18 swirl at 6400 rpm and about 53-54 mph. A Nu-Jet 5.0 is the right propr for a 750. Try it and see what happens. I still don't see how you can pull that 15/20 but you are doing it somehow.

[warfare]

According to the polaris manual the Polaris 5131371 prop is a 15-20. It is a 3 blade with lots over overlap and looks just like a Skat that I have for my 780. I didn't buy it originally so maybe it has been modified from it's original form or the polaris manual is wrong on the specs for the 5131371. Does someone from IMPROS visit this borad maybe they can chime in on the 371 specs

[warfare]

I have currently done the following tune:

Highs 2.5 turns out and the plugs are barely rich enough. Should I go up a jet size?

Lows 1 turn out and loads up on idle and hesitates / dies when going to WOT after extended idling / .25 throttle(2900rpms / 5mph). Tried Tuning it out with the lows but unsuccessful. I believe I need less pop-off pressure.

Pop off I don't remember what I set it to. I believe I need less than stock and what I have now since I have the Ocean Pro Vortex F/A.

Any suggestions would be greatly appreciated...

FYI, With these mods previously posted I can run with a friends 99 XP Limited 951...

[warfare]

My transition to full throttle from 1/4 was a lean hesitation. Since I have the OP F/A I was advised to go to a 105 jet from the stock 90. I installed those today but have not tested in the water yet. Pop-off was deemed ok since I can run rich on the bottom end but lean on the highs. I installed the 105s and have the high needles 1 turn plus the stock settings. Lows I turned back to 3/4 which is 1/4 over stock since I do not want it to be lean. I hope to make progress during testing.

[warfare]

The 105 jets have solved my problem and the ski is running awesome 54mph out of a 750 on GPS!!! Thanks again Sharps Marine, u ROCK!!!!

[surveyguy]

warfare, I have not done any engine mods, did you get lots more power out of switching to the reeds and spacers? Did you have to do any machining, or are they bolt-on?

Also, what is your compression (just want to compare to mine).

Thanks!

[warfare]

Reeds and spacers are more for acceleration. They bolted right on. Compression is 150psi and they are 1.0mm over.

[SeaLion]

Are your heads modified because a 750 new will never see 150 psi on a calibrated gauge even at sea level? My 95 SL750 ran about the same speeds with similar mods. I had the OP rideplate and I added stock Polaris sponsons to mine. I had a swirl 13/18 in there and the pump cone spacer. The sponsons might have slowed me down a mph but the handling was worth it.

[1fastxc]

I'm curious warfare what you are using for an intake grate. I have a 95 sl 750 with boyesen reeds, reed spacers, op f/a's. I still have the stock 90 mains but the high screws are out 1.5 turns. The plugs look ok to me. I have a skat 13/18 imp. and an op ride plate. I'm also using an r&d scoop grate. My ski runs between 6270-6310 at wfo. The weird thing is my speedo says 47.3mph. I haven't had a chance to use a gps yet, but was just curious if the intake grate could be screwing up my mph reading? I will be putting on an extended pump too, but i want a baseline first to see what/if any improvements it makes. Also, Sea lion is there any gain to using the pump cone extension? I have one but seen on another post not to use it. Thanks.

[SeaLion]

I too had the extended pump and that's what I saw my 53 to 54 top speeds. The intake grate will mess up the speedo reading and it will actually slow you down quite a bit (if you have the big wing one that R&D sells). The pump cone spacer will yield higher top speed but hurt bottom end a little bit. I was happy with my set up. I had reeds and milled heads so my bottom end loss was never noticeable.

[1fastxc]

Thanks Sealion. The intake grate that i have is just the shorter wing. How much do you think that'll slow me down? I really need to get it on the gps. I'm very curious. How do my rpm's seem to you?

[SeaLion]

They actually seem fine for your set up. With the short pump, I never liked the top loader. Then again, I didn't have the short pump for very long. I went to the extended pump a year after buying my new 95 SL750 and pretty much did most of the mods at the same time. BTW, I just remembered that I also had a 6* wedge with my short pump. Talk about shooting up a rooster tail trimmed all the way up. I kept it even after my extended pump went on and it tamed the extreme up trim and no more rooster tail. I still run a 6* on my SLX780.