problems with Kawasaki 750ss porpoising badly

[dogknott]

I'm fairly new to the forum and have so far got some great info with helping me re-do my old G.W. Invader so maybe someone can give me some insight on my problems with jet ski. It's a 95 or 96 model 750ss Kawasaki I bought a few years ago real cheap. It's always ran/rode really good until this past year. Seldom do I have the ski in the lake, spends most of its time in deeper rivers here locally. I first had some cavitation problems last year but have since resolved that issue but in place of one problem comes another it seems... From about everything I've searched & read these 750ss are notorious for porpoising especially riding 2 up. It's doing it so bad now that it's near impossible to even ride single without being bounced off the seat. It is completely stock right down to the original ride plate & intake grate. From what I've gathered most people install aftermarket ride plates & intake grates to help with porpoising. And some get by with shimming the rear of the ride plate. Anyone have any suggestions with helping with this?? I can sometimes stop the porpoising by backing off throttle and getting back in it but last time out that seemed to not really help. any help would be greatly appreciated and I'm know theres a bunch of guys on forum that know their sh*t!!! Hoping some of em will see this and point me in right direction!! Thanks!

 

[jbetzelb]

Re: problems with Kawasaki 750ss porpoising badly

Sometimes ski's that tend to porpose some anyway get worse with impeller wear. You might check how much space you have between your impeller and the pump jacket the impeller is sitting in. I don't know how much space is in tolerance for your machine but it is very little space on any jet ski. I recently had to replace my polaris impeller and pump jacket due to a broken shaft but it was amazing how much better my ski rode and propelled with new parts. Literally drove line new. IE, my impeller must have been worn.

 

[dogknott]

Re: problems with Kawasaki 750ss porpoising badly

I'm assuming the pump jacket you're referring to is the pump housing the impeller sits in? I was going to order an impeller tonight but I'm going to hold off a few days. I'm going to pull impeller tonight and check condition of the pump housing and verify how much clearance I've got

 

[dogknott]

Re: problems with Kawasaki 750ss porpoising badly

also what pitch impeller would you recommend for a stock jet ski? 9-17?

 

[sixfigures]

Re: problems with Kawasaki 750ss porpoising badly

those came with electric trim the trim usually goes bad and is quite expensive to repair so most people disconnect the arm from the trim motor to the nozzle so it will level itself out when the ski is running, however your trim may still work , if it does someone may have changed the angle of the nozzle and the bow is rising up, check the nozzle angle see if it is pointing up even just a little will make it do what you are experiencing.

 

[jbetzelb]

Re: problems with Kawasaki 750ss porpoising badly

Yes I said pump jacket but it is the pump housing. The space on my 2002 polaris is suppose to be around .020 with a feeler guage. I would stick with he stock impeller pitch. There should be a number on it and that shouold cross reference with non-factory brands also. I assumed the trim was working. If your trim is not working and it is set wrong that would be the number one porpoise issue.

 

[dogknott]

Re: problems with Kawasaki 750ss porpoising badly

sixfigures this model doesn't have any kind of electric trim I'm almost positive. it's a 95 model Kaw 750ss

 

[sixfigures]

Re: problems with Kawasaki 750ss porpoising badly

I had one years ago and it did have a trim the motor was mounted near the back of the hull on the left side . looked triangular with 3 screws holding the cases together and a cable exiting the hull to the nozzle a switch was on the left handle grip

 

[dogknott]

Re: problems with Kawasaki 750ss porpoising badly

I wish this one had trim but itd be one more thing to tear up! ill post pic of what ive got

 

[dogknott]

Re: problems with Kawasaki 750ss porpoising badly

well as of last night I got the first coat of paint on bottomside finally. One thing I found on bottom of hull right in the V was a place that had pretty much busted thru and allowing water inbetween hull. Pretty sure I dont even have to ask this, but this would definitely cause problems due to water "catching" on the split and not moving thru water smoothly & the added weight of any water leaked inside? It's my fault I know from beaching it on river banks & such several times over the years

 

[sixfigures]

Re: problems with Kawasaki 750ss porpoising badly

If the hull is taking on water that will make the bow rise at speed as the water goes to the rear of the ski, those kawasakis had very weak glass near the ride plate, mine was soft and needed to be totally reglassed to make it work correctly ,later the back was totally torn off while pulling a tube, the ski was very unstable and liked to tip over going slow One day I hit a piece of wood that was floating in some rough water, the board went right through the hull and sank the ski in a few seconds with no warning I didn't even know I hit anything just one minute I was going through the waves and the next thing I knew I was in the water swimming.
As for the bottom being weak if the hull is soft it will usually cause a power hook making the nose go down and plow water not up as yours is doing.

 

[dogknott]

Re: problems with Kawasaki 750ss porpoising badly

good point. Regardless it couldn't have been helping any so I went ahead and fixed a few needed spots. Like you mentioned about the area around ride plate, I had an encounter with a decent size submerged log while riding the river with the wife on the back. I was just running enough speed pretty much to keep it on a plane, looking back if it would have just been me on there I'd been running a lot faster & shallower in the water and it prob wouldn't have happened. it busted pretty good chunk right where the rear of intake grate is. And the last time I had it out it did seem to "plow" the water. It was actually kicking water up from the front left of ski underneath. It's never done that before either till then. You'd think this would be my sign that jetskis aren't intended for creeks/rivers?...

 

[sixfigures]

Re: problems with Kawasaki 750ss porpoising badly

I am surprised you had 2 people on that ski. My rule is a 2 seater is really a 1 seater. And those were exceptionally narrow.

 

[dogknott]

Re: problems with Kawasaki 750ss porpoising badly

yea I know they are super unstable at a stand still, x10 with addition of an extra person onboard. But surprisingly really stable when up to speed IMO

 

[thumpar]

Re: problems with Kawasaki 750ss porpoising badly

I had the XI version (electric trim and twin carb). The trim was the only thing that kept it from stable. I had to rebuild the motor but it didn't cost me anything. I still have the stock 5 blade impeller from my XI.

 

[bently]

Re: problems with Kawasaki 750ss porpoising badly

I had one (750 XI) back in the day. I had an Ocean Pro ride plate with an R&D intake grate both of these components improved out of the hole and acceleration. The ride plate helped with the porposing. You may find these parts on Ebay if you are lucky because I do not believe they are made anymore. You can also extend the jet nozzel 1 to 3 inches, this will also help with your issue but take some know how to complete properly. This jet ski is one of the funnest skis, the best jest ski ever made in my opioin is the '99 late release Ultra 150.

 

[MikDee]

Re: problems with Kawasaki 750ss porpoising badly

I had one of these with power trim I think it was a 96'. A few washers under the ride plate at the back helped keep it from porposing. I don't remember how many, but you want it to be lower in the back. I got the info from a jetski forum. It might have been 3 washers at the back, declining to 1 washer in the front?

 

[sixfigures]

Re: problems with Kawasaki 750ss porpoising badly

I believe my ski was a 750ss I bet if you found a used parts dealer and purchased a used trim style nozzle and cone with the trim ring you could easily build a manual trim adjustment like the old sea doos had, once you get the nozzle set where it works best you leave it alone and you are fine.