19 replies to this topic

[Aussie]

Has anyone increased the RPM of the rev limiter?
Is it advisable and whats the easiest way?

[Kevin Leclair]

Unfortunately I have never messed around with my rev limiter, maybe someone else on the site here has some insight on this?

[Bob86ZZ4]

Unfortunately I have never messed around with my rev limiter, maybe someone else on the site here has some insight on this?

I would think that SeaDoo (and Rotax) have many engineers that know a lot more about their engines than any of us doo. I'm betting they set the rev limiter to the maximum safe rpm's where they can feel confident the engine won't destroy itself. I've got no experience in modding a Rotax but I have some in the small block Chevy area. Unfortunately it seems to go hand in hand, the more you push the performance level the more breakdowns. I bet you could mod the heck outa the engine and get better performance and not have more repair issues but I wouldn't just tinker with the rev limiter. It's gotta be a package deal, like lighter weight parts, freer breathing, freer exhaust, more compression, etc.... What about checking with some of the jet ski performance places that mod up the SeaDoo's? I think this is a great topic but sounds expensive too. My wife always reminds me when riding in my boat, "there's no reason this boat needs to go this fast."

[thumper]

wow - just how fast does a speedster 160 go?

[Bob86ZZ4]

wow - just how fast does a speedster 160 go?

Mine is a '96 Speedster 14' twin 720cc 85 h/p. On smooth water with just me aboard it'll do 50mph as shown on my gps. Don't trust somebody that tells you there's goes xx mph as shown on their speedometer. The speedometer is only a guess at the actual boat speed.

[thumper]

i have been informed (by my dealer) that i can expect 65mph from the 2005 scic sportster - does this seem ok or is it a tad exaggerated?

[Kevin Leclair]

Well the real way to test it would be via a radar gun or a GPS that has an accurate speedo. Sometimes the SeaDoo speedo is a tad off.

[tiggerman]

i have been informed (by my dealer) that i can expect 65mph from the 2005 scic sportster - does this seem ok or is it a tad exaggerated?

Sounds a bit on the high side... maybe if it were a ski with the SCIC, I would believe it...

[Doooer]

i have been informed (by my dealer) that i can expect 65mph from the 2005 scic sportster - does this seem ok or is it a tad exaggerated?

He probably meant 65 kmph.

[tiggerman]

i have been informed (by my dealer) that i can expect 65mph from the 2005 scic sportster - does this seem ok or is it a tad exaggerated?

He probably meant 65 kmph.

So that would be roughly 40-45 MPH.....

[Scarface]

40-50 mph is plenty fast enough for me, especially when someone is pulling me on a tube. That's too fast then!

[AlabamaScott]

40-50 mph is plenty fast enough for me, especially when someone is pulling me on a tube. That's too fast then!

Ive never tweaked out mine, but im willing to bet it'll be awsome... i'm on a smooth lake and dont think twice about filling it up with expensive fuel, and if you ever check out walmart or a local car store you can get some stuff they call "boost", but its just highly volitale gas... a couple of those babies and i break 60mph easy... thats testing it against my fisherman buddies outboards with gps that i always smoke because of the get up and go my seadoo's got..

[Aussie]

Gee what was the topic again?

[Kevin Leclair]

Gee what was the topic again?

Yeah its seem to have deviated a bit, but this just happens from time to time.

[4man]

Getting back on topic, raising the rev limiter without dooing other modifications is not going to help. Every engine, but especially 2 strokes, have an RPM where they produce their peak horsepower. If you have a dyno chart to look at, you will see the horsepower curve up and up and at some point, it must change direction and curve down. The highest point of the curve is where the manufacturer takes their horsepower reading and they usually give an RPM as well. The prop or impeller selection for a boat is usually made from that figure.

For example, let's say you have a boat making 240hp at 5300rpm. If with a 19 pitch prop (propeller moves ahead 19 inches every revolution) running at wide open on the lake with one person, almost no gas, slight ripple on the water etc. you notice that your tach says 5500rpm and you are doing 60mph. You could change to a 20 pitch prop and bring the rpm down and your speed up as you will be closer to the peak hp of the engine. Just remember, with a 20 pitch, on a day with some chop, full tank of gas, 5 people, etc. the boat may be slower.

But also, the rev limiter on that boat from factory is probably set at 5700 rpm, so even if you change it to 6200rpm, it won't make any difference. The only way it matters is if you change the porting, pipe, compression ratio etc. and change the point at which the engine makes its power. Then even after changing the rev limiter, you may have to change prop/impeller to take full advantage of the change. The only reason that sea-doo's and sea-doo boats have rev limiters is for when you launch them out of the water or cavitate badly and there isn't enough water drag to slow the impeller down.

[tiggerman]

'bout time.... where you been? Your informative answer is much appreciated!

[4man]

It's been a long winter! I meant to check back more often, but hanging out in here just makes me miss the doo!

[tiggerman]

That's why mine is where i hafta walk past it everyday......

[Torx Racing]

Were able to raise the rev limiter on any 4 tec engine.. Check out our website for more info www.torxracing.com

[Douglas Young]

Were able to raise the rev limiter on any 4 tec engine.. Check out our website for more info www.torxracing.com

Missed the point