[pilot_172]

I took my newly acquired 2004 Yamaha FX HO to the lake today and noticed some problems that hopefully aren't severe. When i took it out by myself it worked great... the pick up was a little slow but it got right up to 45-50 mph. I then went to the beach and picked up a couple of friends to take them for a ride. As i tried to accelerate the waverunner rpm'd up to 10000-11000 but wouldn't go past 15mph. I recently checked the air filter, changed the oil and gapped the plugs. The machine has 97 hours and probably original plugs... could old plugs be causing this or does it sound like something else could be at fault. The impeller does have a few little nicks....how would that affect performance??

Thanks for anyone's input

 

[6atenza220]

Hi, the most important thing you can do to any watercraft is change the spark plugs and fuel filter. This should be done at the start of every season. Given that it is newly acquired, I'd just start with that. That should correct it but as I've experienced with my own recently aquired gp760, this may not always be the case. Also check for water in your gas. Good luck!

 

[pilot_172]

Took the waverunner out again today after changing all 4 spark plugs and no change noticed from the day before.... still bogging down under a load of 2 people

 

[~mike]

I don't see how it's possible to get that kind of RPM with no speed unless your intake grate is plugged. Perhaps you sucked up something when you went to the beach to pick up your friends.

Mike

I took my newly acquired 2004 Yamaha FX HO to the lake today and noticed some problems that hopefully aren't severe. When i took it out by myself it worked great... the pick up was a little slow but it got right up to 45-50 mph. I then went to the beach and picked up a couple of friends to take them for a ride. As i tried to accelerate the waverunner rpm'd up to 10000-11000 but wouldn't go past 15mph. I recently checked the air filter, changed the oil and gapped the plugs. The machine has 97 hours and probably original plugs... could old plugs be causing this or does it sound like something else could be at fault. The impeller does have a few little nicks....how would that affect performance??

Thanks for anyone's input

 

[pilot_172]

but this is my second trip out and i'm having the same problem. I actually took the intake grate entirely off before i went and inspected things. I stopped by my local shop today and asked the service techs there. One guy suspected that maybe the impeller has enough nicks that its causing cavitation. Can anyone back this up?? would that seem likely?/

 

[GCwaverunner]

Remove the pump shoe, seal all surfaces that come in contact with the bottom of the ski with sikaflex and replace. The pump shoe seal may have finally blown out. Check the impeller to liner gap (should be about 2-3 thou). And small nics on the impeller will airate the water causing cavitation. I cant believe your local dealer couldn't tell you this. This is the most basic problem all Yamaha's have and such an easy fix. The dealer must not do many skis.

 

[~mike]

I've got nicks on my impeller and I have no problems with 2 riders and pulling 200lbs+ on a tube behind it. I guess it sounds like your not building up pressure at the impeller. If you tip your trim up and nail the gas, does it shoot water out 20ft+ or does the engine just rev?

 

[pilot_172]

Thanks for the input gcwaverunner. I am new to the world of waverunners and not quite sure what or where the Pump shoe is at. When you talk of using the sikaflex, is that to seal the intake plate and ride plate? I looked at the impeller and it does look nicked up but also the impeller duct assembly has some edges with alot of pitting. Is this a result of cavitation?

 

[GCwaverunner]

exactly, the pitted holes are a result. There may be some on your impeller blade faces too. The pump shoe is the thing right underneath the ski which the scoop grate bolts to. It directs water to the impeller. It has 4 x 12mm bolts. Remove the scoop grate first obviously ( 4 x 10mm bolts). Sikaflex (silicone doesn't work, need very sticky stuff) the pump shoe wherever it comes in contact with the ski including the bottom of the pump ring. No need to sikaflex the ride plate or anything else. Obviously clean it so it is neat and tidy with a little acetone. Also, check the impeller gap. Should be from 2-4 thou.

 

[pilot_172]

Great.. thats just what i needed to know. I will pull it apart and make sure it is all sealed up. So can just the smallest non-sealed areas on the pump shoe make a large difference?? what is your take on the pump shoe seal kits??
Thanks

 

[GCwaverunner]

When you take the pump shoe out you will notice large cavaties inside it that can hold air so yes it will make a huge difference. The pump plug kits will fill those cavaties but you will still have to seal it up anyway. I usually just fill those cavaties with sikaflex in place of the kit and make sure I seal all surfaces connecting to the hull. Its the same and its cheaper.

 

[pilot_172]

well i sealed the shoe plate up real good and took the waverunner out to the lake today.... put it in the water and the problem is still the same. Where would you look next?? i'm thinking i need to get to the impeller to measure clearance and probably replace...

 

[~mike]

So at full throttle you're only getting 15mph with one rider? Is the hull full of water?
Does the ski ever plane out?
You can probably shine a light through the steering nosel and see the clearance. Mine has probably 1/32" all the way around.

 

[pilot_172]

thats full throttle with 3 people... by myself i can get it to plane and accelerate to about 45mph...

 

[GCwaverunner]

Why did you not measure the clearance when you had the pump shoe out???? 2-4thou remember. Why would you not inspect the impeller closely while you could access it easily??? Anyway, if you have sealed the pump shoe in correctly and filled ALL the cavaties with sikaflex, and I mean ALL the cavaties and the impeller clearance is good and there is nothing blocking the intake grate, and the engine is revving to 10,000RPM, there is no reason why it is not performing.

 

[~mike]

Is your trim adjusted to push the nose down? That would cause you to lose some speed and maybe causes the ski to never plane out with 3 people on it due to the weight

How much weight are you putting on it with all 3 riders?

 

[SgtBarrett]

I experienced this same issue last weekend with just 2 adults on the ski (2 200lb men). It took a very slow rev to get the ski going. Just slamming the throttle caused us to go nowhere. Eventually we got on plane and hit >50...
With me and my 2 smaller kids (70lb each) we had no problems getting onto plane.

I thought we had sucked something into the intake. But it was clean. I did the inspections today and did not notice any pitting and the impeller is flawless.
The trim, however, is stuck in neutral. cant go up or down with it... Will have to work on that this weekend.