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Author Topic:  Jetski Motor Hrs. Is 1000hrs really a lot or not!  (Read 8505 times)

Offline David & Megan

Jetski Motor Hrs. Is 1000hrs really a lot or not!
« on: April 03, 2017, 09:26:32 PM »
Jetski Motor Hrs. Is 1000hrs really a lot or not!

Jetski Engine Wear & Tear (Seadoo) vs Car Engine Wear & Tear

I wrote this the way i see it. Any other thoughts would be welcome.

Jetski Engine Wear

1/ If a jetski has 150hrs on its clock then to presume its average speed is 45km per hr it travels 6750 km.
2/ The hrs are clocked up over 2 yrs this is 3375 km per year.

Car Engine Wear
If a car travelled 3375 km in a year this would be considered Extremely low! So lets do numbers on a car driven by a non commercial entity.

1/ If a family car travels 25,000 km per year at an average of 45km per hr this equates to 555.55 hrs per year.
2/ This would be considered very low km's for a car if the motor snuffed out at this stage of it's life.
3/ So if we get real and say the engine did 150,000 km this equates to 3,333.33 hrs. At this many km's some car engines are still good to go, some are done and out. So lets say the car engine is "done and out".

This means a jetski motor should be able to perform well over 3000 hrs?
But- Are the conditions the same? One must consider-
Revs
Heat
Conditions
Load
Movement

Lets consider:

Revs- ok the jetski revs higher. But it is an engine designed to do this for a long time. Put that aside and compare:
Mums and Dads drive the car around the streets, start stop around town. It gets driven hard somedays some not. Gears change so engine revs up and down far more than a jetski especially in traffic.
My Mazda does 2000rpm at 110kmh.
My Commodore does 1750rpm at 110kmh.
My wife's muzzzbox screams at 4000rpm at 110kmh
and My Turbo Dessel ute does 3800rpm at 110kmh (2005 model with 148,000 km on the clock)

To be fair lets say the jetski does twice as much work (i doubt it though),
Therefor the jetski engines life span is 1/2 of the car engine reducing it to 1500hrs in this case.

Heat-I am not sure about this one, maybe somebody could help?

Conditions- Marine vs Road

I have had marine motors a long long time and never had a problem until i STOPED using them. Keep them moving and maintain them and all is good.
Marine components are built for a marine environment that is why jetski's are so expensive. The components are better quality than a car engine.

Therefore no reduction in the jetski life for conditions.

Load-I am pretty tough on my cars. I don't speed but i like to get to the speed limit quick as. So i do put a lot of load on the car motor. Not an expert in this but in would think the jetski being significantly lighter and the fact that water slips compared to tar roads the load would be less.
Now add a trailer to a car! My commodore towed my 2 tonne Haines often. Thats load.

Therefore no reduction in the jetski life for load.

Movement-boats slamming down on the waves would be more impact than a car could dish up and the case that a jetski's engine is centred compared to a boat with an outboard the jetski engine gets a pounding.
However, this wouldn't affect the wear in the cylinders rather in things like the crank shaft. I relay on the fact that the jetski engine is built to a higher standard for this impact compared to a car engine.

This is my way of looking at the matter, anybody have any thoughts love to hear from you







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Offline Mandy

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Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #1 on: April 04, 2017, 04:18:11 PM »
Great work David  chr


The world is very hard on a Jet Ski motor.


We do see them going like a train at 2000 hours but occasionally they're absolutely buggered at 30-50 hours with loss of compression, broken engine mounts stuffed pumps etc.


It really depends on care taken with maintenance I think and of course - keep riding them  blma

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Offline David & Megan

Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #2 on: April 04, 2017, 05:26:27 PM »
Great work David  chr


The world is very hard on a Jet Ski motor.


We do see them going like a train at 2000 hours but occasionally they're absolutely buggered at 30-50 hours with loss of compression, broken engine mounts stuffed pumps etc.


It really depends on care taken with maintenance I think and of course - keep riding them  blma
How old are the jetski's with low hrs and stuffed engines?


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Offline Mandy

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Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #3 on: April 04, 2017, 05:56:49 PM »
Sometimes only a few months old 😅

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Offline David & Megan

Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #4 on: April 04, 2017, 09:04:56 PM »



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Offline johno

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Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #5 on: April 05, 2017, 12:40:51 PM »
 gp I've had this discussion as number of time with some pretty wise heads, including some great chats with Mandy going back a few years. for what its worth this is my take on the issue. I believe there are a number of factors at play, which I will try to justify briefly.

Load - the drag on a hull even when planing is enormous. example- let go of the trigger at any reasonable speed and until the ski slows to something approaching displacement mode, it would compare to something like moderate braking in a car or on a bike. that drag is there all the time the ski is on the plane, meaning that at a constant speed your power input needs to be the equivalent of the drag, something around the same drag as moderate braking, or in words, like driving around with foot planted firmly on the brake in your car.

To put this into real world comparisons roughly speaking a 200hp motorbike will top out something like 260kmh where a 200hp ski will top out at say 110kmh. Physics tells us if you double the speed you quadruple the drag (and triple the speed, drag is multiplied by a factor of 9), so assuming driveline efficiencies are similar at any given speed, the drag on the ski's hull will be 5.5 times that of the bike. So that load exists basically anytime you are off idle!

operating conditions- are harsh and the constant presence of moisture around the exhaust must be a factor when most of us don't fog our four strokes. like Mandy says, using the skis regularly must assist in blowing away any corrosion on the components before it becomes a problem.

Design- these things are high performance engines. horsepower per litre is prob around double of road going vehicle engines so any comparison there there might be not helpful. horsepower comes at a cost - longevity. Formula 1 race engines are designed to detonate at about 24 hours under current rules. it used to be 2 hours (when they had better efficiency).

Operator use- are we not out there to have fun? of course we are going to use full noise often.

All in all, our great little machines run high performance engines at high RPM with high load levels in a harsh environment and we give them a solid towelling. I'd be pretty happy if mine gets to 600-800 hours.  dno
« Last Edit: April 05, 2017, 02:52:41 PM by johno »
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Offline Kave

Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #6 on: April 07, 2017, 12:27:35 AM »
Johno, thanks for taking the time to  explain. Makes sense. I hope my ski goes 600-800.
Kave


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Offline David & Megan

Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #7 on: April 25, 2017, 04:43:14 PM »
gp I've had this discussion as number of time with some pretty wise heads, including some great chats with Mandy going back a few years. for what its worth this is my take on the issue. I believe there are a number of factors at play, which I will try to justify briefly.

Load - the drag on a hull even when planing is enormous. example- let go of the trigger at any reasonable speed and until the ski slows to something approaching displacement mode, it would compare to something like moderate braking in a car or on a bike. that drag is there all the time the ski is on the plane, meaning that at a constant speed your power input needs to be the equivalent of the drag, something around the same drag as moderate braking, or in words, like driving around with foot planted firmly on the brake in your car.

To put this into real world comparisons roughly speaking a 200hp motorbike will top out something like 260kmh where a 200hp ski will top out at say 110kmh. Physics tells us if you double the speed you quadruple the drag (and triple the speed, drag is multiplied by a factor of 9), so assuming driveline efficiencies are similar at any given speed, the drag on the ski's hull will be 5.5 times that of the bike. So that load exists basically anytime you are off idle!

operating conditions- are harsh and the constant presence of moisture around the exhaust must be a factor when most of us don't fog our four strokes. like Mandy says, using the skis regularly must assist in blowing away any corrosion on the components before it becomes a problem.

Design- these things are high performance engines. horsepower per litre is prob around double of road going vehicle engines so any comparison there there might be not helpful. horsepower comes at a cost - longevity. Formula 1 race engines are designed to detonate at about 24 hours under current rules. it used to be 2 hours (when they had better efficiency).

Operator use- are we not out there to have fun? of course we are going to use full noise often.

All in all, our great little machines run high performance engines at high RPM with high load levels in a harsh environment and we give them a solid towelling. I'd be pretty happy if mine gets to 600-800 hours.  dno
If a jetski had 6 gears would it go faster than 110kmh?


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Offline Mandy

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Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #8 on: April 25, 2017, 05:19:50 PM »
Absolutely, the problem is how to put in an auto gearbox.


Diesel would allow a bigger prop but at lower revs probably not much gain.


There is only one way to get Skis faster as we are bottlenecked by the size and length of the pump tunnel. We can only go as fast as the water can exit the nozzle.


Any alteration to that set up and you no longer have a Jet Ski.


So we need direct drive with much higher revs.


One word TESLA


Electric engines will give us astronomical torque to push steep pitches and the ability to rev to 20,000 rpm.  The future looks very bright indeed.


 wh





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Offline David & Megan

Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #9 on: April 27, 2017, 07:40:33 PM »
Absolutely, the problem is how to put in an auto gearbox.


Diesel would allow a bigger prop but at lower revs probably not much gain.


There is only one way to get Skis faster as we are bottlenecked by the size and length of the pump tunnel. We can only go as fast as the water can exit the nozzle.


Any alteration to that set up and you no longer have a Jet Ski.


So we need direct drive with much higher revs.


One word TESLA


Electric engines will give us astronomical torque to push steep pitches and the ability to rev to 20,000 rpm.  The future looks very bright indeed.


 wh
Wow the speed demons will love that. The ski's will race out if the retailers door.
Turn the mechanics into sparky's!


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Offline David & Megan

Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #10 on: May 13, 2017, 08:45:02 PM »
Spoke to a jetski hire company mechanic today about this subject and the dreaded Seadoo carbon seal.

He said" we rebuild the engine at 1700hrs!!
Carbon seals go 800hrs. Main reason they fail, engine mounts fail or are loose leaving little or no pressure from the bellow ".

The hire jetskis probably are treated far better than the jetskis in the private sector as they are restricted by both the hire company and the engine managment system and are far less likely to be run up on sand banks or trailers at boat ramps and don't sit in a garage doing nothing rusting their cylinder sleeves out.


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Offline johno

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Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #11 on: May 14, 2017, 10:02:52 PM »
 Carbon seal 800 hours? Maybe if you never flush it. My first set were whining like a teenager at 200 hours. Second set made 150 hours.
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Offline David & Megan

Re: Jetski Motor Hrs. Is 1000hrs really a lot or not!
« Reply #12 on: May 15, 2017, 06:50:03 PM »
Carbon seal 800 hours? Maybe if you never flush it. My first set were whining like a teenager at 200 hours. Second set made 150 hours.
Mine has lasted 175 hrs. The manufacture says they have been known to last 30,000hrs on commercial vessels. I reckon they do max 12 knots prob only 2500 rpm. I think i ran mine to long on the trailer and it got to hot.


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