96XP scored pistons

phinq · Joined: 18 Aug 2007 Posts: 3

Help me solve the mystery.
The boat ran good for about 20 minutes, then lost about 300 RPM and the
throttle response was not as crisp. It acted as though it had a fuel
problem, but fuel system checked out.
For grins, I checked compression and found that it is low on both cylinders,
normally 185, but now 155. I bought a piston set, then pulled it apart last
night. Both pistons were heavily scored on the bottom skirt (opposite of
exhaust). The rings were not effect (yet), but the skirts were ugly.
Cylinders check out good, within factory spec.
Boat is stock other than Proks, and R&D rec. head. Engine has about 100
hours since last rebuild.
I am not sure why this happened. I had changed the RAVE valve caps to
aluminum tops bought from a shop in Florida, but that is the only real
change made recently. I am suspecting I did not let it warm up properly, or
my oil pump may be lean. It was replaced at the beginning of the season.
Why did this happen?

Archived from group: rec>sport>jetski

Dan Costello · Joined: 18 Aug 2007 Posts: 6

conver to premix and you shouldn't have that problem. the boat went lean
and the pistons stuck

get the oil injection block off kit, use some higher octance fuel and
premix your gas and oil and you should be fine

"phinq" wrote in message$926.1201@sccrnsc03...
> Help me solve the mystery.
> The boat ran good for about 20 minutes, then lost about 300 RPM and the
> throttle response was not as crisp. It acted as though it had a fuel
> problem, but fuel system checked out.
> For grins, I checked compression and found that it is low on both
cylinders,
> normally 185, but now 155. I bought a piston set, then pulled it apart
last
> night. Both pistons were heavily scored on the bottom skirt (opposite of
> exhaust). The rings were not effect (yet), but the skirts were ugly.
> Cylinders check out good, within factory spec.
> Boat is stock other than Proks, and R&D rec. head. Engine has about 100
> hours since last rebuild.
> I am not sure why this happened. I had changed the RAVE valve caps to
> aluminum tops bought from a shop in Florida, but that is the only real
> change made recently. I am suspecting I did not let it warm up properly,
or
> my oil pump may be lean. It was replaced at the beginning of the season.
> Why did this happen?
>
>

phinq · Joined: 18 Aug 2007 Posts: 3

I found that the new oil pump was putting out far less oil than the old
pump. I don't want to convert to premix out of laziness, I premixed fuel for
WetBikes for many years and don't want to go back.

phinq

"Dan Costello" wrote in message@comcast.com...
> conver to premix and you shouldn't have that problem. the boat went lean
> and the pistons stuck
>
> get the oil injection block off kit, use some higher octance fuel and
> premix your gas and oil and you should be fine
>
> "phinq" wrote in message
> $926.1201@sccrnsc03...
> > Help me solve the mystery.
> > The boat ran good for about 20 minutes, then lost about 300 RPM and the
> > throttle response was not as crisp. It acted as though it had a fuel
> > problem, but fuel system checked out.
> > For grins, I checked compression and found that it is low on both
> cylinders,
> > normally 185, but now 155. I bought a piston set, then pulled it apart
> last
> > night. Both pistons were heavily scored on the bottom skirt (opposite of
> > exhaust). The rings were not effect (yet), but the skirts were ugly.
> > Cylinders check out good, within factory spec.
> > Boat is stock other than Proks, and R&D rec. head. Engine has about 100
> > hours since last rebuild.
> > I am not sure why this happened. I had changed the RAVE valve caps to
> > aluminum tops bought from a shop in Florida, but that is the only real
> > change made recently. I am suspecting I did not let it warm up properly,
> or
> > my oil pump may be lean. It was replaced at the beginning of the season.
> > Why did this happen?
> >
> >
>
>