-
This site contains eBay affiliate links for which Sea-Doo Forum may be compensated.
hiow long can a 787 run at WOT?.
- Thread starter drake1
- Start date
- Status
Spimothy Leary
Well-Known Member
right up to the point where it seizes up and dies.
personally I keep my wot runs under a minute unless i'm running from da cops.
personally I keep my wot runs under a minute unless i'm running from da cops.
Dr Honda
Well-Known Member
realistically... if everything is spot on... they could run out a tank at a time. Over, and over.
I've held my Seadoo's wide open for over +20 minutes chasing newer skis... but normally I go to about 75% power if I'm on a long ride. (5500 to 6000 RPM) Besides... they get better mileage at lower settings.
I've held my Seadoo's wide open for over +20 minutes chasing newer skis... but normally I go to about 75% power if I'm on a long ride. (5500 to 6000 RPM) Besides... they get better mileage at lower settings.
SabrToothSqrl
Well-Known Member
No reason for it to stop if its in good shape. I only know WOT.
bell99man
Active Member
I didn't know they had any other position.
Hmmmm, I think I here a challenge! I know, I know, it didn't happen unless it's recorded, but can any of you young seadoo psycho's manage to run out a full tank at WOT the whole time? Maybe we could get parts sponsorship from our advertisers?
Kevin
Hmmmm, I think I here a challenge! I know, I know, it didn't happen unless it's recorded, but can any of you young seadoo psycho's manage to run out a full tank at WOT the whole time? Maybe we could get parts sponsorship from our advertisers?
Kevin
Kind of OT but related- speaking of WOT and reliability, I was amazed by the RPM difference between the Seadoo skis and Skidoo sleds. Similar motors run 2000 more RPM's in the sleds and are reliable, yet some question the reliability of a Seadoo at WOT.
A friend and I were just having this conversation the other day. A stock skidoo 800 is clutched to run ~8200 or so, that would be unheard of on an 800 ski. Is it the load difference or what that makes them hold together in the sleds?
A friend and I were just having this conversation the other day. A stock skidoo 800 is clutched to run ~8200 or so, that would be unheard of on an 800 ski. Is it the load difference or what that makes them hold together in the sleds?
Strizzo
Well-Known Member
Sbt already does durability testing on their reman engines, they say that their short blocks outlast factory engines in all tests. They wouldn't give details on the tests or mtbf though
Strizzo- SBT can make statements like that about their engines because they cut their heads(squish bands) less aggressively. This means that you could run lower octane fuel and/or have your timing off a bit and still be OK. If I made engines with a "no fault" warranty then I would do the same thing! It also means that one test they did not win is a side by side race with all other factors being equal(IMO).
Some WOT riders will hear a pinging sound eventually. Whether or not you let off the throttle at that point usually makes the difference in a buildable or"non-rebuildable" core.
Some WOT riders will hear a pinging sound eventually. Whether or not you let off the throttle at that point usually makes the difference in a buildable or"non-rebuildable" core.
CLAYMORE
New Member
That's good to know... It was my belief that WOT on a ski or boat was not actually the redline for these Rotax motors but an optimal high RPM that produced max torque and horsepower... So, is the max RPM the 8200 as stated and seen in the snowmobiles? What is the max or the redline for these motors, anyone know?
I personally enjoy WOT!
It seems to me to be around 6950-6960. I'm basing that only on my personal experience. There does not seem to be an honest 7000 without an aftermarket rev-limiter.
I get what you are asking and I think you are right...you just dont run a sled wide open for miles at a time you vary the throttle much more on a sled than a PWC.
I typically dont hold mine open longer than 15-30 secs...I vary my throttle all over.
Matt I love your Avatar more every time I see it. Westside Powersports baby!!
I typically dont hold mine open longer than 15-30 secs...I vary my throttle all over.
Matt I love your Avatar more every time I see it. Westside Powersports baby!!
Strizzo
Well-Known Member
there is a calculation you can do to determine mean piston speed, which will determine approximately at what rpm wear begins to become severe, and engine life is greatly reduced. this depends a bit on the components used, but is usually between 3500 and 5000 feet per minute. I remember reading an article about it in a pwc magazine way back in the day, they said that above the max piston speed, engine life is measured in minutes rather than hours.
here is a better explanation than i can muster: http://www.mustangsandmore.com/ubb/SteveWmaxpistonspeed.html
here is a better explanation than i can muster: http://www.mustangsandmore.com/ubb/SteveWmaxpistonspeed.html
Spimothy Leary
Well-Known Member
i'm in total agreement short wot runs are much better than long runs. I used to do a ton of long wot runs on my yami 760 partially because I didn't know any better and partially because it only ran 49mph so I was always pushing near wot just to keep up with my buddies with faster ski's, i went thru two top ends in 3 years, but that was over 200 hours of running. now that my ski run's 60, i can cruise at 45 w/o hitting the throttle too hard. (so far only 1 top end in 20 months on this ski)
Depends on where you ride and how you ride lol. I have been on some pretty long flats where it is to the bar for quite a while
. For the most part though- yeah, you do vary it a lot more on a sled than a ski. Just found the RPM limit differences odd when comparing the two. Also thinking it may be a power issue too- They certainly don't have the power to turn a stock impeller to 8000+ and if you were to prop down to get the RPM, I don't know how "torquey" it would be mid range on and off the throttle. If they set the limiter to 8500 and prop it for 6500, that is a huge shock when the thing gets unloaded and loaded up again and will probably do more harm than good.
Last edited by a moderator:
Strizzo
Well-Known Member
heres an interesting thing, i got to thinking about whether mean piston speed might be a factor in the short life of the 951s, according to that site, to determine max rpm you can divide the engine stroke by the appropriate factor based on engine components.
the stroke on a 951 according to the 1999 shop manual is 3.079 inches. if you take 21,000 / 3.079 you get 6820.xx... heavy duty (forged pistons, rods, crank etc.) nets 7794.xx...
many people on here advocate a full rebuild any time a top end is needed on a 951, this could well be the reason for such short lifespans of the 951s compared to the other rotax engines. does/did any company ever make aftermarked forged internals for the 951s? i wonder if forged parts in otherwise stock motors could make them a bit more predictable engine life.
the stroke on a 951 according to the 1999 shop manual is 3.079 inches. if you take 21,000 / 3.079 you get 6820.xx... heavy duty (forged pistons, rods, crank etc.) nets 7794.xx...
many people on here advocate a full rebuild any time a top end is needed on a 951, this could well be the reason for such short lifespans of the 951s compared to the other rotax engines. does/did any company ever make aftermarked forged internals for the 951s? i wonder if forged parts in otherwise stock motors could make them a bit more predictable engine life.
CLAYMORE
New Member
So, based on the above I got off my ath to do some math...
787 has a stroke of 2.91". 21,000 / 2.91 = 7216 rpm. Actual RPM at WOT is 6800-7000 so that means that we are operating 200-400 rpm less than the absolute redline. Damn Close and definately in the red zone on the tach IMO...
Good enough for my curiosity, thanks for the information that provided the mathematical solution.
Last edited by a moderator:
Hmm, going by that formula, that would explain why the main caps walk so badly on my turbo 351 windsor
.
Strizzo
Well-Known Member
Hmm, going by that formula, that would explain why the main caps walk so badly on my turbo 351 windsor
lol if you click the link in my post before that one, it actually starts out with "why can the 289 rev to 7,000 on stock internals while the 351 will come apart well below that?"
BMANN06
Well-Known Member
I did it once but in a boat (1998 speedster 2x787s) not sure if it counts or not. And I didn't quite run it dry ... just to the point where buzzer was going off. $130 poorly spent but fun none the less.
Spimothy Leary
Well-Known Member
i have the waterways to do it... i think i could run the peace river at wot for a full tank, but there would be some hairy turns around the 30 mile mark, i'd prefer not to hit them at 61
but I like my ski too much (and my skull)
i have the waterways to do it... i think i could run the peace river at wot for a full tank, but there would be some hairy turns around the 30 mile mark, i'd prefer not to hit them at 61
At WOT 100% you would miss all the pretty babes in the thongs.....
i have the waterways to do it......... but I like my ski too much
And your shoulder
Spimothy Leary
Well-Known Member
At WOT 100% you would miss all the pretty babes in the thongs.....
And your shoulder
lol, the thongs in arcadia are better off seen at 60mph. but honestly the peace is the only place where I think I could do a full 50 miles of WOT, everywhere else has at least 1 or two no wake zones or would be too choppy. maybe you could do about 10 big circles at Lake Placid or something i dunno. not important, i'll never do it on my 2 stroke, although i think there's less damage that could be done on a 4 stroke.
Haha, that's great! I would have just answered "because it's a Ford" lol. Yes, I own one, but no, I'm not a fan of their motors at all. Just happens to be what I had the itch to build at the time
.LMAO, I can attest to that!
I honestly didn't realize the Peace River was that big. I have only been maybe a couple miles north of Navigators. Need to do some more exploring! I just don't trust these things not to leave me stranded
.
Spimothy Leary
Well-Known Member
LMAO, I can attest to that!
I honestly didn't realize the Peace River was that big. I have only been maybe a couple miles north of Navigators. Need to do some more exploring! I just don't trust these things not to leave me stranded
oh hell's ya, you can go thru arcadia, past brownsville and a good solid 50 miles up from there (assuming its been raining, can't be done during the dry season) it goes further than my tank goes, that's for sure, but we've launched from the 760 ramp (arcadia) and also from brownville road and headed north from there. thats where you find the twisties !!!!
when you get a chance, watch adambomb's video.
[video=youtube;QAK2MailmXU]http://www.youtube.com/watch?feature=player_detailpage&v=QAK2MailmXU[/video]
there's more but this is an idea of how far north they got... its not a "great" representation of the twisties, but its pretty dam good.
- Status
