2002 Sportster LT Performance Questions

[slingo56]

Hi

Have a recently acquired 202 Sportster LT with the twin 717 85HP engines.

Notice that one engine has a tendency to rev up to 7000 frequently when not that much throttle is applied. If I back of a bit on the throttle it will drop back down to where is should be. What could be causing this?

Also, tried to get a 210lb water skier up with about 400lbs of passengers in the boat and the boat didnt have the power to do it. Would this be expected? Boat seems to take longer than I would expect to get up on plane in general. Once it does, it sure seems to go like heck but it seems slow to get there. Any thoughts?

 

[Waterluvr]

How recently acquired is it, or in other words approximately how many hours have you ran the boat personally? I ask because your issue is one that can stem from a seal / air leak in the case causing a lean out condition in your fuel air mix and those are usually less noticeable at first, often initially overcome by enrichening the carburetor low and high side and ultimately developing into a more prevalent issue such as what you have now.

 

[slingo56]

We just inherited it and used it for the first time last Friday. It had not been used at all this season prior to that but was supposedly serviced for the season early in the spring at which time one of the starters was replaced.

 

[Waterluvr]

Ok, often what I find on a motor behaving that way having had the same owner for the duration of the problem is that the carburetor settings have been enrichened to compensate for an air leak, either by the owner and or their mechanic. As an air leak gets worse, the high and low side adjusters are increased to try and compensate for an engine that runs at a much higher rpm than it should at a given throttle position. You will also find elevated engine temperatures when run in a lean condition and a noticeable loss of power. I always use a remote tachometer to double check the readings from the dash gauge as well.

A slight adjustment of 1/4 to 1/2 turn out over time is normal for many engines that have carbs in need of servicing and cleaning, full turns or more of an adjuster beyond established settings are a sure sign someone is trying to tune an engine with an air leak.

In your case, I would remove the carbs and record the number of turns required to seat the high and low side adjusters and then compare those to the factory setting specifications. This will at least tell you some useful information as to whether this issue has been addressed previously by attempting to enrichen the fuel circuits.

It's always a good idea at that point to conduct basic compression and ignition tests on the motor, your symptoms are not common for cases where the carbs just need a good cleaning and rebuild with new kits for the diaphragms etc. and especially if they start and idle well until such time a heavy load is placed on them.

 

[Sportster-2001-951C-Stock]

Hi

Have a recently acquired 202 Sportster LT with the twin 717 85HP engines.

Notice that one engine has a tendency to rev up to 7000 frequently when not that much throttle is applied. If I back of a bit on the throttle it will drop back down to where is should be. What could be causing this?

I assume you mean this happens when the boat is operating in the water. If yes, it seems either there's a problem with the drive shaft splines (worn out) or the impeller is being ventilated by an air leak. At this point I'd guess the PTO splines are probably worn out.

If these motors run away on the trailer, there could be a crankcase air leak somewhere, such as a missing carburetor base gasket or leaking outer crankshaft seal allowing air into the crankcase, but they can't/won't run away like that while in the water unless there's a drive line problem.

Edit: "or the impeller is being ventilated by an air leak." By this, I mean to say the impeller is actually turning at the same RPM as the engine but it's not "hooking up", for whatever reason. It's not always caused by ventilation of the impeller, it can also be caused by cavitation due to a damaged wear ring in the jet pump. If you climb underneath and look up inside there shouldn't be more than s dime's thickness of clearance between the impeller and the wear ring. If rocks and debris were sucked up through the jet pump the composite wear ring may be torn to shreds.

 

[slingo56]

Thanks for the feedback.

Would this also explain the lack of initial acceleration to get up on plane or pop a largish skier up? Perhaps I was being overly optimistic in my expectations of how quick the boat would be. I think it is still fast at the top end but seems lacking in getting up to speed.

 

[Sportster-2001-951C-Stock]

Thanks for the feedback.

Would this also explain the lack of initial acceleration to get up on plane or pop a largish skier up? Perhaps I was being overly optimistic in my expectations of how quick the boat would be. I think it is still fast at the top end but seems lacking in getting up to speed.

"tried to get a 210lb water skier up with about 400lbs of passengers in the boat and the boat didnt have the power to do it."

If you're used to a stern drive boat perhaps, there's a big difference and the jet isn't quite as forgiving in terms of popping challenging loads out of the water, IMO.

But I think it's possible for you to pull this skier with this amount of weight aboard depending on if the jet pumps are in good condition and hooking up as they should also the skill level of the skier helps. If he was on two skies that should be a piece of cake but on slalom he may present a bit of a challenge that requires finesse with the throttles(incremental application can help reduce cavitation). If he's experienced he will probably tell you the boat doesn't quite pull as strongly as others he's skied behind and that's probably true.

That said, I haven't skied behind the twin engine Seadoo you're running, I'm doing a bit of guessing based on how my 130HP Seadoo pulls, but the driver has to ease into the throttle to avoid cavitating the impeller and maximize pull, slamming the throttle to WOT position too quickly before the boat begins moving the impeller seems to cavitate and can lose it's hookup.

But if your jet pumps are in need of rebuild b/c the wear rings around the impeller are scarred and torn up from rocks and debris then you will leave a lot of power on the table, in this case the pumps will be much easier to cavitate and you will experience difficulty getting the boat moving.

 

[slingo56]

Skier was on 2 skis and is experienced. Sounds like I did make a mistake though as I did go full throttle right away and did not ease into it... at all. Will have to try that next time and with a smaller skier as well.

As I say, once on plane the boat seems super fast just seems slow to me in getting there. Notice this with anymore than kids in the tube as well.

 

[dbracela]

Just to confirm, it revs up high and quickly, but doesn't get moving quickly? Like a clutch slipping on a manual transmission car? If so, you're describing cavitation (more or less). Common reasons are: worn out wear rings, worn out driveline seals (carbon ring assembly), pumps improperly sealed to the boat (use neoprene seals when putting them back on), out of spec or damaged impellers. All of these things are fairly easy fixes, and can be done at home. Search "cavitation" and you'll find a gazillion threads on it, and if you need a walk through almost everyone on here has been through it and can help you out.
If you're looking to tow with a lower horsepower seadoo, look into skat-trak swirl impellers. They're excellent for helping with bottom end oomph and hook up very well, even in heavy chop. We were skiing all day today, three people and two fat dogs in the boat plus the skier.

 

[slingo56]

That is exactly what it sounds like. Thanks everyone for the feedback!

We have such a short season here I don't want to lose a couple of weeks of it getting this addressed. Will likely live with it and then get it dealt with in September when the boat gets put away. One upside is it sounds like it will seem like a whole new boat performance wise once this is fixed!