What would make a 1996 GTX do this....

[jchance]

I have replaced the engine in one of my 1996 GTXs with a SBT short block. We went through the engine break-in procedure last weekend and everything appeared to run just great. By the end of the 2nd tank, it reved great, had a good power curve and response.

My sons are at our lake house this weekend (I have to work) and report back that it is now not running well. They put it in and ran the battery down cranking last night as it was hard to start and the fuel valve was turned off! After they got it started, it ran great for 5 to 10 minutes and then just died. They told me that it wasn't like the DESS key being pulled; that it just suddenly ran poorly and then died. They couldn't get it restarted (said the battery was weak) and towed it in. I told them to pull the plugs and make sure that something hadn't happened to the engine. They said that it turned over fine then and thought the battery was the issue. They left it on the charger overnight.

They cranked it again today and said it was again hard to start and ran a little rough; like the timing was off. After idling for a few minutes, it began to run fine again and they took it out. After 5 to 10 minutes, with it running perfectly normal again, it again suddenly died and was hard to restart. Now they are calling long-distance to see if I can point them in the right direction.

I need to add that while the engine was out, we cleaned and adjusted the carbs, replaced the filters, put in a new RV shaft, replaced the RV valve and replaced the RV cover (all by SBT).

The oil pump was primed and we ran extra oil in the first 10 gallons as recommended by SBT.

Anyone know where to go from here???

[woodsrider40]

Re: What would make a 1996 GTX do this....

Did you rebuilt the carbs and check pop off pressure?

[jchance]

Re: What would make a 1996 GTX do this....

The carbs were rebuilt with good pop-off pressures and the fuel lines and valve were all replaced 4-5 years ago.

When my son called yesterday, he said that it starts fine after being on the charger overnight. It will run for about 10 minurtes and will then simply shut down. Yesterday he was able to restart it and run about 5 more minutes before it again shut down. Of course, like most 20 year olds, he was running pretty much at full throttle and jumping wakes. It then acted like the battery was low and had to be towed back. I am leaning toward an ignition or charging problen, I think. Also, could it be a bad battery? I have an identical GTX that he is swapping the battery today to see what happens. If not the battery, where to go next?

Can a GTX run on a low battery? How long can a GTX run on just the battery alone?? Can it run w/out a battery? I am using dry cells and I think that this one is either 1 or 2 years old (hard to keep the 2 GTXs apart sometimes) and always kept on a tender. If the battery is not charging, then I will check the rectifier next. The only prioblem is that they will not be back home until tonight and I'm not where they are!

[woodsrider40]

Re: What would make a 1996 GTX do this....

My GTX would not run right with a low battery & like you said it may not be charging and overloading the stator making it shut down, yes check the rectifier next, put in a good battery and have a volt meter on hand then start it with meter on battery post to see if it reads a little higher then 12 volts, if not more then likely the rectifier could be bad but check all the conneters to make sure they are clean.

[jchance]

Re: What would make a 1996 GTX do this....

Spoke with SBT today. They are wondering about a seizing engine. Got boat home today and checked compression. 150 PSI in PTO cylinder and only 70 in the MAG side. Pressure jumps to 110 PSI after squirting in a little oil. The break-in procedure was followed "to a T" and we even added some extra oil to the 2 following tanks of gas after the 1st tank. It is still on and had recently just started on that 3rd tank! I gotta wonder what happened to the MAG side of the engine. Will be in contact with SBT in the AM.

Is it common with rebuilt engines to burn a ring this soon?? We are using the oil injection system and it was checked before reassembly and as I said, we also have added extra oil to the gas so far to insure the break-in went smoothly.

One other question which is slightly off the thread: my old GTX engine was white and the replacement is silver. Is it normal to get a different color given the year it is replacing?? I thought that they tried to match the color of the rebuilt engine with the original one.

[dsolie]

Re: What would make a 1996 GTX do this....

Engines fail, they are 2-strokes, in a marine environment.. That's why SBT has a warranty.

Also, they paint them to the newest OEM color code for that motor (in the 2000's they changed motor colors)

[jchance]

Re: What would make a 1996 GTX do this....

Spoke again with SBT and was told to pull the engine and send it back. I got it out and took a look at the pistons and rings through the exhaust port. The PTO cylinder is pristine with a completely normal looking piston, rings and cylinder wall. The MAG side looks like crap. The piston has vertical marks along the side of the piston and the cylinder has the same, but much less.

Of course, the first questions from SBT concerned the fuel system, carbs, filters, etc. It looks to me like a blown ring or incorrectly installed one. Would think that it did not have enough lubrication if I had not added extra oil to each tank; the current one included. Will post the final outcome when I know it.

So far I have been impressed with the SBT folks.

[jchance]

Re: What would make a 1996 GTX do this....

Hopefully last update--sent engine back to SBT where they went through it. The MAG piston was toast. They argued that it was a lean issue and was caused by my carbs or an intake leak. I reminded them that they had replaced the rotary shaft/valve/cover and retimed the engine themselves. I had just gone through the carbs not once but twice and knew that they were not the problem! They were absolutely clean and the only thing not done to them was the needle and seat. I ordered a new set of rebuild kits and needle/seats and cleaned/rebuilt them for a third time.

They finally sent me back an engine and still insist that there had to be an intake leak. So be it! I reinstalled the engine 2 nights ago and started the break-in procedure again yesterday. We got as far as ready to start running at 90% before it got dark. We finished the procedure today and all is well. One interesting thing to note is that this engine started and runs MUCH better and smoother than the first! I still have to contend that I was sent an engine with a problem to start with, but SBT made it right despite thinking that it was a problem at my end. I am hitting 6750 RPM at WOT and 54-55 MPH in fairly rough water.

[Rocky 1]

Re: What would make a 1996 GTX do this....

The carbs were rebuilt with good pop-off pressures and the fuel lines and valve were all replaced 4-5 years

If it were mine and they said it was lean burn it could have been a stuck needle/seat. if it is in warranty they don't care what happened to it they just told you so you could fix the problem, Thats is just the way they are. There for you. u might check the fuel tank vents they will clog and give you a lean condition. good luck

[Rocky 1]

Re: What would make a 1996 GTX do this....

By the way what part of tenn. i am from kingsport. tri cities area

[jchance]

Re: What would make a 1996 GTX do this....

Just outside Memphis.