1998 Sportster 1800 Melted Electrode

[Ktmrider77]

Hello my nautical friends,

First, I have to say...I have read many posts on this site and it's like one big family with a wealth of information, Kudos to everyone! Bought this boat a few months with the intention of having some fun with my kids. It ran good for a couple lake trips and then the issues started. It has the Twin Rotax 717 engines and I will start with the most pressing issue.

The fastest it ever ran was about 37 mph WOT. Two trips ago we were 10 minutes into our voyage at cruising speed around 6000 rpm and Starboard motor sputtered, came back and then died. Limped back to dock on one motor. Got it home and both plugs were fouled with no spark. Tried 2 other plugs and got spark, so I went to the parts store and bought 2 platinums and added some Stabil to the tank.

Went back out this weekend, almost same thing happened after 10 minutes...but this time one plug melted and the other looks rust color...really clean or really lean. Noticed when I tried to crank it over before removing the plugs..it seemed to turn slower.

Also maybe worth noting...my air cover was off cause I forgot to put the clips on, I cant imagine that made it run lean though

Got it home, pulled off the head, Broke a head bolt off... The front piston is a little pitted...more so around the edges but nothing like I thought it would be. Cylinder looks smooth.

Where do I go from here? I'm not even sure what went wrong or was going wrong on the first trip? Injector pump? Do I go ahead and do top end rebuild / hone cylinders? Pull the motor? Buy a new motor, or just burn the boat where it sits SBT seems to be the place to go for engine parts.

Im a single dad with 2 boys...time is not on my side. Thank you!!!

 

[ialonso]

It would seem you are running lean. Too much Air and/or not enough fuel are the underlying causes.6,000 RPM is low for WOT. lack of airbox will cause you to not reach max RPM (I know first hand, but does not account for such a low RPM. I could still hit 6600 with no airbox on my 717s put it back and got to 6950 with new pump wear rings.).

Check compression, make sure it's within specs. that will determine what you can consider as it relates to hone/replace of pistons and cylinders.

How are your carbs? 90% of issues related to Max RPM and engine sputtering are related to carbs on the 717. Clean Fuel is mandatory. Check your fuel filters, and even with it, the carb will run a few years top notch max, then needs to be cleaned and rebuilt (or replaced, which sometimes is not that much more expensive)

 

[Ktmrider77]

Thank you for the response Ialonso.

It would run at 7000 rpm with no problem...I was cruising at 6000 when the issue took place. Carbs probably need to be addressed and I will change the filters. I will try to extract the broken head bolt so I can put the head back on and do a compression test.

 

[howie099]

Without the air filter cover on you would suck more air. I would look for a clogged fuel filter. Dieing out under load or in the turn under load is the first signs of it. Should just look at a whole engine because of the year unless you know if the engine has been replaced.

 

[Ktmrider77]

Thanks Howie,

So the opinion seems to be fuel flow / carb related. And I'm gathering that
Replacing an engine on this type / year boat is certainly not uncommon...SBT has engines for $800. It does smoke More than I would expect upon start up or sitting, I'm told it's from a seal that starts to leak oil.

 

[howie099]

I replaced the fuel pumps and rebuilt the carbs on both engines. My engine smokes for like 10 minutes at the dock. I look like a hillbilly there. My crank seals are leaking on my one engine. I am going to get them rebuilt this winter. I don't prefer and SBT engine, I would look at the other rebuilders like SES or Fullbore. Both I think offer you a much better product. The warranty work of course is not as fast since they don't pump out engines like McD's sell hamburgers. The choice is up to you. I use SBT for a lot of other things...

 

[Ktmrider77]

Thanks Howie!,

At least our boats are not surrounded by flying insects. Of course we are political outcasts with all the pollution they expel but thats ok, the Ozone is overated. Anyway...what other companies would you suggest for all my SeaDoo needs? Did you replace your fuel pumps with OEM or the dual Makuni setup I have read about? Easy way to make sure my oil injector is working properly?

 

[howie099]

I used SES(Seadoo Engine Shop) and Fullbore. Right now fullbore is give an extra year warranty so you get 3 years instead of 2. I did do the dual mikuni and plugged one. The last I looked they don't sell the sportster 1800 ones anymore. I bought the Mikuni DF52 pumps. It was like $70 for 2 or them. I was able to mount them on the OEM brackets. I just JBwelded the one port and put a plugged hose on the end in case the JBWeld broke loose. I did add some aftermarket marine external fuel filters also. The clear ones that you can see in them.

The easiest way is to replace the little lines on the oil pump and you can watch the oil go up when you pull the oil pump lever all the way. For me I would do it when you gas is low so you can add some oil to the tank for added protection. You can take the pumps off and run them on a drill and measure the oil out put if you want.

 

[Ktmrider77]

Very Good Info...thank you Howie.

 

[Ktmrider77]

Well friends, I could not get the broken head bolt out, so I decided to pull the jug and proceed with a new top end. Fortunately or unfortunately, I noticed the connecting rod was not spinning as freely as one would expect...sure enough, pc of the bearing was wedged between crank and rod. Need to rule out everything that caused the failure and order a new engine. I understand the idea of thread lock...but they need to back off the LocTite...broke 5 bolts pulling and breaking down the motor. Thanks again for all the good feedback.

 

[racerxxx]

No loctite on those, they get grease on the threads and blue removable loctite under the head of the screw to help seal the flange of the screw.

Sent from my SGH-T889 using Tapatalk

 

[Ktmrider77]

Thanks Racer X,

When I disconnected the oil feed line at bottom of crank case- starter side of motor...the oil was flowing. Is it safe to assume, lack of injector oil to crank was NOT the reason for spinning a bearing?

Should the backside of the "cover" that encloses the Rotary valve have grooves in it? Looks just like a music CD but with ports.

And when I took that cover off, A clear liquid with texture of oil and scent of gas came out.