New to me 91 GT

[91GTRider]

Hey everyone,

This is my first post here as I just bought a non running 1991 Sea Doo GT with the 587 Yellow engine. It had a locked up engine from sitting without fogging oil but I got that fixed and the ski is now running. There are a few issues that are preventing it from running ideally and wanted to ask the folks here to see if there's anything I should look at other than what is listed below.

#1. The engine will bog down and not run smoothly when it is first started in the water. It will do this for a while (maybe 10-20 min) then run just fine. Having no idea when the last time the fuel system was even touched on this, I plan on going through all of the lines, filters, and doing a carb rebuild. Are there any recommendations for carb kits? I want something that's good quality and the ones I see on amazon for $15 seem a little to cheap to be any good. Any recommendations at other things to look at fuel system wise?

#2. I noticed some 2 stroke oil on the engine mounts after running. Enough to make me look for any broken or loose lines. I found very thin rubber line on the intake side of the engine below/next to the carbs that was cracked and leaking oil. I plan on replacing it and going through the all the oil lines and replacing whatever needs to be replaced, along with the oil filter. Do the oil pumps ever go bad on these? Do I need to take the injection system apart and clean it or should I just replace the lines and filter?

#3. There seems to be a lot of noise coming from the jet area. The sound is high pitched and may be normal but I'm not sure. I have checked the jet pump oil ,which was full, and the metal collar that is on the PTO shaft, right before it passes through the hull has plenty of grease. Is it worth removing the whole jet assembly and checking bearings for wear or is this normal?

I'm sure I will have more questions in the future. I have a lot of experience working on small engines and have an automotive engineering degree but 2 strokes are not really in my wheelhouse.

Thanks in advance!

 

[91GTRider]

Bump

 

[AKnarrowback]

Only rebuild the carbs with genuine Mikuni parts. You will hear this a million times on this forum for good reason. The aftermarket kits are junk. Go to OSD Marine and order a carb kit with a needle and seat, the original parts are a bit more expensive but 100% worth it. Use the carb rebuild thread in this two stroke section as a guide to get the job done right. I highly recommend having a set of JIS screwdrivers for the carb work. The carb rebuild needs to be done no questions about it. DO NOT add any extra fuel filters, the stock filter/water seperator is good enough along with the fter screen inside the carb itself. Be VERY CAREFUL with the pop off arm spring, gently remove it from the carb and re-use it, do not stretch, bend cut or modify it in any way. Pop off pressure is very important in these carbs and that little bugger is a vital part of making things run right. Even if the carb kit comes with a replacement spring re-use your original, unless your pop off pressure is terrible when doing the check.

If you have grey fuel lines they need to be replaced BEFORE you do the carb rebuild. The oem fuel lines deteriorate inside, gum up the carb and kill motors. Go to napa and get regular 1/4, black, automotive fuel line.

The fuel selector switch can leak air into the system and cause problems. Agsin, only buy oem, aftermarket ones leak out of the box and will cause problems.

Get that oil leak figured out. If the two small lines going from the pump to the inlet fittings are leaking that is an engine killer. Again, go to napa and get some replacement hose.

The oil pumps on sea-doos are VERY reliable. DO NOT take the system apart. Just make sure the filter is good, lines are secure, the pump is bled after the lines are replaced and the timing marks are spot on.

The noise from the rear is tougher to give an answer on. Yes, pull the pump off, drain it and inspect things inside. Look at both ends of the drive shaft splines and see how much wear you have. If you have access to a motor alignment tool give that a double check. I ran my 94 xp with the motor out of alignment and had a whine develop in the drivetrain within 45 minutes of riding, I caused some wear in the pto flywheel splines that still is in the background even after replacing the driveshaft.

Let us know how things are going.

 

[91GTRider]

Only rebuild the carbs with genuine Mikuni parts. You will hear this a million times on this forum for good reason. The aftermarket kits are junk. Go to OSD Marine and order a carb kit with a needle and seat, the original parts are a bit more expensive but 100% worth it. Use the carb rebuild thread in this two stroke section as a guide to get the job done right. I highly recommend having a set of JIS screwdrivers for the carb work. The carb rebuild needs to be done no questions about it. DO NOT add any extra fuel filters, the stock filter/water seperator is good enough along with the fter screen inside the carb itself. Be VERY CAREFUL with the pop off arm spring, gently remove it from the carb and re-use it, do not stretch, bend cut or modify it in any way. Pop off pressure is very important in these carbs and that little bugger is a vital part of making things run right. Even if the carb kit comes with a replacement spring re-use your original, unless your pop off pressure is terrible when doing the check.

If you have grey fuel lines they need to be replaced BEFORE you do the carb rebuild. The oem fuel lines deteriorate inside, gum up the carb and kill motors. Go to napa and get regular 1/4, black, automotive fuel line.

The fuel selector switch can leak air into the system and cause problems. Agsin, only buy oem, aftermarket ones leak out of the box and will cause problems.

Get that oil leak figured out. If the two small lines going from the pump to the inlet fittings are leaking that is an engine killer. Again, go to napa and get some replacement hose.

The oil pumps on sea-doos are VERY reliable. DO NOT take the system apart. Just make sure the filter is good, lines are secure, the pump is bled after the lines are replaced and the timing marks are spot on.

The noise from the rear is tougher to give an answer on. Yes, pull the pump off, drain it and inspect things inside. Look at both ends of the drive shaft splines and see how much wear you have. If you have access to a motor alignment tool give that a double check. I ran my 94 xp with the motor out of alignment and had a whine develop in the drivetrain within 45 minutes of riding, I caused some wear in the pto flywheel splines that still is in the background even after replacing the driveshaft.

Let us know how things are going.

Thanks AK, that's all great information and exactly what I was hoping to find out. I ordered the genuine Mikuni kit that you mentioned and will use the guide you mentioned to rebuild the carbs. Luckily there are no grey fuel lines so I'm assuming that they were replaced by the previous owner.

Is there a way to test the fuel selector switch and see if it is leaking air into the system?

I ordered a bunch of parts like the replacement oil lines, a new oil filter, and will figure out how to bleed the system when it gets to that point. Is there a guide or posted procedure on how to bleed the oil pump?

Regarding the jet pump, I ordered a wear ring since mine looks pretty scuffed up so I will take a look at splines and the driveshaft whenever I have the pump disassembled.

I'll keep updating this thread with my progress. I'm hoping to have it back up and running soon since the season is coming to a close faster than I will admit to myself lol. Regardless, I'm happy with my purchase since I got it with an aluminum trailer for $600.

Thanks again

 

[AKnarrowback]

http://seadoomanuals.net/manuals/1991-seadoo.php