SL 780 Speeds and RPM

[ZiGz]

What kind of Top End speeds should I be getting from an SL780 and what RPM should it be running at WOT?

Rider = 250 lbs (no wisecracks :P )

[WATERCRAFTSERVICES]

Re: SL 780 Speeds and RPM

52 Mph @ 6750 if tuned and running properly

[ZiGz]

Re: SL 780 Speeds and RPM

52 Mph @ 6750 if tuned and running properly

So if I'm running at WOT on a nice little chop or even smooth water the RPMs should be that high? They only get close to that when impeller comes out of the water.

What could cause the lower RPMs (~ 5500 WOT)

Could low compression? Right from the day I got the motor (SBT) the compression was 110 across the board which seemed a little low but I wanted to confirm with another guage.

[321nolan]

Re: SL 780 Speeds and RPM

I have a SLT780, it hits just above 6300rpms at WOT...I am not sure if everything is correct? Max speed if my speed sensor is working properly is aprox. 50mph

[Modtodd82]

Re: SL 780 Speeds and RPM

I've Got a 94 SL750 , a new NuJet 5.0 impeller. The other night on glass it was turning about 6120 rpm and my mfd showed 55.3..........., i didnt use my GPS but next time i go out i will take it with me, and i'll se what it does on gps.

[321nolan]

Re: SL 780 Speeds and RPM

I have a 96 SLT 780...I removed my impeller to find out it's a polaris 17-23 out of a Polaris Genesis and it's in poor shape. What size impeller are you running, would a 14-19 have good bottom end and mid range power? Mine has no bottom and mid power really, it pulls hard at 4300 rpm's and above but that's it.

[scott71]

Re: SL 780 Speeds and RPM

I am currently running a 96 slx780. Mods include .50 over bore, tdr waterbox, and an r&d intake grate. I weigh 235lbs and my best recorded top speed on my mfd shows 63.7 mph at 6550 rpm. This can only be achieved on a very calm day with slight ripples on the water. I know the mfd is not 100% accurate but I still think I am getting great top speed out of this bike. Hope this helps

[Polaris_Nut#1]

Re: SL 780 Speeds and RPM

Stock 96 SLX 58.8 mph at 6,310 rpm. Not on glass, but not major chop either.
R&D intake grate only mod, 205 Lbs rider. In the low 60's when my buddy rides it weighing in at 145 Lbs.


95 SL 750, 56.4 Mph at 6,210 rpm. 205 Lbs. rider

Boysen Pro Reeds
Reed Spacers
Primer Kit
O.P. flame arrestors
CHANGED the exhaust cooling orifice from the 2.3mm to the 1.0mm (gained about 100 rpm)
skat-trak stator 6 vien
6 degree pump wedge
cone extension
R&D intake grate
O.P. ride plate
28 inch sponsons
Bored exit nozzel
14/19 swirl impeller
4 Inch extended pump.

Anyone have any thoughts as to what the 750 will turn if I switch to a 13/18 impeller? I'm looking for more top end. It's just right on the bottom now. Comes out of the hole like an monster.

[Polaris_Nut#1]

Re: SL 780 Speeds and RPM

52 Mph @ 6750 if tuned and running properly

I believe that's banging the rev limiter right about there. It is not going to happen without modifcation to the engine.