FX140 seems slow

bellmd · May 31, 2009

We bought a used 2003 Yamaha FX140 with 81 hours and it seems to be slow for a 140hp waverunner. We had a VX110 and it was alot faster than this one. The motor seems to rev up well but it feels to me like there is a slow response from the jet drive, I can't explain it well but the motor revs up quickly and the jet drive seems to take a long time to respond. The jetski will eventually get up to about 40-43mph and seems to top out there, I had expected more like 50-55mph. The motor also seems to have a slightly rough idle (not sure if this is a prob tho) but is very smooth when revving up to speed.

Since I'm a newbie to working on waverunners I was wondering if someone could give me some basic things to check in the jet drive before I blindly just go haul this thing down to my local dealer for their diagnosis? Thanks in advance for any tips or ideas.

JayDawg · May 31, 2009

A few things to check. Check compression in each cylinder, replace the spark plugs and possibly plug wires, and check your drive shaft and impeller for damage.

bellmd · Jun 1, 2009

I've got some spark plugs coming, is there a simple procedure to checking the drive shaft and impeller for damage?

JayDawg · Jun 1, 2009

The most simple thing to do is if your jet ski is on a trailer is to crawl underneath the rear of the ski and examine it through your intake grate. Is there anything bound up or around the shaft? Is the shaft straight? With the impeller, look at it's edges and see if they are damaged from and rocks or sand that may have been sucked up in them.

bellmd · Jun 2, 2009

Impeller shaft is clear of objects and the leading edges look great so I'm not sure what is wrong. Motor only revs up to 8600rpm at full throttle though, I pulled the plugs and they looked ok, checked the gaps and they were good. Air filter looked good too. Any ideas on the low RPM?

JayDawg · Jun 3, 2009

Has to be your carbs then. Well, at least most likely. Clean them out and see if any linkages are not working.

bellmd · Jun 3, 2009

I think I'll take it to the shop from here, I'm so lost I thought it was fuel injected. Thanks for the tips/ideas, will report back what the dealer says.

bellmd · Jun 22, 2009

New plugs solved the problem - although they looked fine apparently one was not firing. PWC is running very well now, thanks.

JayDawg · Jun 22, 2009

Glad you fixed the problem! I have seen jet ski's do some very strange things and all it turned out to be was the spark plugs needing to be replaced. I learned a very long time ago to always keep 1 or 2 extra sets of plugs on me when I go to the river, lake, bay or ocean.

trurider · Jun 26, 2009

bellmd said:
New plugs solved the problem - although they looked fine apparently one was not firing. PWC is running very well now, thanks.

Was it hard to change the spark plugs?? I'm getting ready to change mine, any advice.

fedorov5549 · Jun 27, 2009

Take the top of the airbox off, remove filter, take off stick coils with 10 mm wrench, remove plugs with I believe an 18 mm socket and long extension. I put a little anti-seize on the threads too.

trurider · Jun 27, 2009

fedorov5549 said:
Take the top of the airbox off, remove filter, take off stick coils with 10 mm wrench, remove plugs with I believe an 18 mm socket and long extension. I put a little anti-seize on the threads too.

Thank you for the information..

FX140 seems slow

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