98 seadoo sportster 1800 engine surging trouble shooting need help

[Black creek cruzin]

The boat has twin 717 engine..right motor blew last summer just had the dealer install a new sbt engine, and wear rings in the back as well as rebuilt carbs on both motors..Boat ran great for 2 weeks and now on start up it runs great and after 15 minuets it starts surging..from 6k rpm to 4k and back and forth. I personally pulled and replaced all spark plugs, opened up both carbs and sprayed down with carb cleaner, changed both the fuel filters by the fuel tank, ran compression test on both motors and they all read almost 150psi. boat is still surging..I have tried running with the fan on to help with air flow and still surging..I am out of ideas. Please help if there is anything else I can try..Also with the new motor the dealer told me to run twice the normal amount of oil..I think the last they told was with 15gallons of gas at a time mix with 35 ozs of oil..Could this be the problem? running to rich? I also put a can of seafoam in yesterday hoping to clear it up. Thanks for any and all help.

 

[LouDoo]

Have the grey tempo fuel lines been replaced? Never put Seafoam in a seadoo. For break in you should be running your regular inject oil and adding oil to the gas tank at 50:1 which would be what you are running. It sounds like its time for a carb. rebuild.

Lou

 

[Black creek cruzin]

fuel lines

Both carbs where rebuilt about a month ago. Can I replace the gray fuel lines with just regualr black fuel lines from autozone? oil injection is blocked off..Only mixing gas/oil now.

 

[vission]

"Never put Seafoam in a seadoo."

I was just curious as to why this is not recommended for the Seadoo?

Thanx,
Vission

 

[LouDoo]

Since you are premixing you need to be using 40:1 at least during break in. And yes use regular black automobile fuel hose, you will also need to clean the entire fuel system, and you may need to rebuild the carbs, again.

Seafoam is a solvent and in two strokes it dilutes the oil needed to lubricate the engine.

Lou

 

[vission]

Hmmm, ok, thanks for the response I'm sure you've had more history with these engines than most of us. I did find this, however it may be simply marketing spiel but their site seems to say it is of good use:

http://seafoamsales.com/sea-foam-motor-treatment/how-to-use-sea-foam-motor-treatment/

Vission

 

[Black creek cruzin]

I got in their yesterday and looked over the fuel lines.. It seems most of them look fairly new and not dirty at all. However I was working on my jet ski which is a 4 stroke and realized it takes special iridium spark plugs...I pulled the ones on my jetboat and the left motor has normal NGKs and the other has champion plugs...can anyone comment on this causeing my surge?? im not sure if it would or not and the correct type of plugs Thanks again

 

[Bonmotwang]

I got in their yesterday and looked over the fuel lines.. It seems most of them look fairly new and not dirty at all. However I was working on my jet ski which is a 4 stroke and realized it takes special iridium spark plugs...I pulled the ones on my jetboat and the left motor has normal NGKs and the other has champion plugs...can anyone comment on this causeing my surge?? im not sure if it would or not and the correct type of plugs Thanks again

Maybe just get a pair of new plugs then you know for sure it is not the spark plug?
Normal NGK is ok, just adjust the gap to 0.021". I tried the "normal" ones and iridium ones, I couldn't tell any differences.


Sent from my iPhone using Tapatalk

 

[jhjesse]

When the carbs were rebuilt did that include needles and seats?? Do you have external fuel pumps?

 

[howie099]

Surging sounds like fuel. That boat has external fuel pumps which I am pretty sure Seadoo stopped making them. Most people retro universal mikuni's and block the extra port. Also your fuel filters could have small leak and sucking air or a carb leak sucking air. I just replaced the whole fuel system. New pumps, new lines, complete rebuild carbs with needles/seats, & new aftermarket car fuel filters($3 disposable or replacement element type). Those OEM fuel filter gaskets have issues ad you can pinch them easy. The only grey/tempo lines on that boat go to the fuel pump so I bet it is all green and gooey inside the fuel pumps. Also auto part store fuels lines will work it is just you will flunk a coast guard inspection not sure whats happens if you are on the water if that happens. Boats have different rules the skis. Remember this boat is 16 years old and I bet the other owners did nothing but drive it. Any 2-stroke you buy you need to replace the whole fuel system right off the bat, it will make you life so much easier..I know I have owned 6 strokes skis all in the end needed the fuel system replaced. all the stuff is not ethenol approved.