'93 Ski Nautique GT-40 Overheating.

[tsassman]

I purchased a ’93 Ski Nautique (my first boat) a couple of months ago at a real good price. Before purchase we took a test drive and really the only issue was sporadic temperature readings. Boat owner said probably needs a new thermostat or gauge. Price was so good I went ahead with purchase. I have all the original paper work from original owner with the original owner’s manual. Original purchase was in Dallas and I purchased it from a guy in Austin. As far as I know it has never seen salt or even brackish water. Don’t know how may owners it has had.

Took the boat to marine shop for a complete checkup (I noted to have him check the temperature issue) and here is what they have done:

1) Battery – Check electrolyte level and specific gravity. Inspect case for damage. Inspect cable and connections.
2) Change engine oil and filter.
3) Change transmission oil.
4) Check and adjust engine alignment.
5) Clean and inspect ignition system.
6) Check and inspect cooling system, drive belt, and exhaust system.
7) Check electrical system for loose or dirty connections and damaged wiring.
8) Clean and inspect flame arrestor and crankcase ventilation system.
9) Check complete engine assembly.
10) Replace fuel filter.
11) Replace raw water impeller.
12) Checked all hoses and clamps for cracks and leaks.
13) Checked all temperature sensors.

His notes on the temperature issues after all this was he tested the boat on the lake and it overheated. He then pulled the thermostat and noticed a large amount of rust in the thermostat housing. He pulled the thermostat, cleaned out the housing and installed a new 160F thermostat. Boat was them retested with the same result – overheating getting close to 200F.

Technician then performed a raw water pump capacity test the result showing proper performance (5 gallons flowed in 15 seconds @ 3000 RPM’s) Circulation pump was now in question but mechanic contacted PCM support technician (Travis Snyder) to discuss issues. Both seem to think that the circulation pump could be weak but due to the manifolds and risers not overheating this is not the main issue. PCM believes that due to the rust issue at the thermostat and water jackets proper flow has been compromised. New circulation pump could possibly fix the issue, but may not be able to perform and better than a weak circulation pump to possible blockage in cooling water passages.

He said the engine might have to be pulled and taken to machine shop to have cooling water passages cleaned out. Sounds expensive!!!! Any thoughts or suggestions on what course of action I should take next?

[DanielC]

How mechanical are you?

[tsassman]

How mechanical are you?

I would say average. But I have good friends that are very good.

[DanielC]

OK, I would try this. Basically, remove the elbow on the circulating water pump, the one on the engine, not the one with the rubber impeller in it. This opens up the cooling engine in the engine pretty good.
Now, get some plumbing fittings from plumbing store, or even a big box home improvement warehouse, and make and adapter that will go from a garden hose, to the diameter of the elbow you removed, and hook that up to one side of the engine where the elbow was. leave the other side open, and use the garden hose to flush out the cooling system.
If you want to improve the flushing action, put a "T" in the adapter you made, and a fitting for blowing compressed air into the water coming from the garden hose.
After flushing one way, flush the other way. Hook the adapter to the port where water was coming out, and flush backwards.

I will take a close look at a GT-40 engine and see if I can give you more details. It just so happens I am winterizing one today.

[flipflop]

Any check engine codes? I would ensure the ECT sensor is working properly first.

[tsassman]

OK, I would try this. Basically, remove the elbow on the circulating water pump, the one on the engine, not the one with the rubber impeller in it. This opens up the cooling engine in the engine pretty good.
Now, get some plumbing fittings from plumbing store, or even a big box home improvement warehouse, and make and adapter that will go from a garden hose, to the diameter of the elbow you removed, and hook that up to one side of the engine where the elbow was. leave the other side open, and use the garden hose to flush out the cooling system.
If you want to improve the flushing action, put a "T" in the adapter you made, and a fitting for blowing compressed air into the water coming from the garden hose.
After flushing one way, flush the other way. Hook the adapter to the port where water was coming out, and flush backwards.

I will take a close look at a GT-40 engine and see if I can give you more details. It just so happens I am winterizing one today.

Thanks for the info. I am picking the boat up from the marine shop in Houston Friday. I will try that this weekend.

[tsassman]

Not sure about any engine codes. I will ask the technician at the marine shop when I pick it up this weekend. Forgive my ignorance but what is the ECT sensor?

[bhectus]

Did a previous owner do a engine upgrade? Because GT-40 engines were not available in '93.

[DanielC]

ECT, Engine Coolant Temperature.
This sensor tells the engine's computer how warm the engine water is. It has nothing to do with controlling the actual temperature of the water.

I took a quick look at the GT-40 engine, and it looks like removing the thermostat cover, with the three hoses, and taking the thermostat out will help you to flush out the cooling system.. It would be a good idea to block water coming out of the hole whrer the thermostat was from splashing on the distributor

[tsassman]

Did a previous owner do a engine upgrade? Because GT-40 engines were not available in '93.

You are correct I just spoke to the technician and it is a 351 PCM Pro Tech. Thanks for the correction.

[gtxragtop]

You stated that it overheated. May now have a blown head gasket. Not sure how to test for this. Easy in a car with a kit from NAPA to sniff for exhaust gases in the coolant

[tsassman]

After having done nothing to the boat since my last post(working alot) and waiting on someone to help me I took it upon myself to pull it out of storage to my house. As noted in my previous post the Houston service tech said he changed the thermostat. I am a below average mechanic and am leary about messing with engines. I took a chance and hooked up a homeade water supply system to my boat to check temperatures myself. I bypassed the water strainer and verified that I was getting water through transmission cooler. Learned a lot about how to do all this on these forums(thanks guys). Without the boat running I was getting water out the rear exhaust. Feeling safe to start the engine I did and temp gradually started climbing till it got to close to 200F and this is where I shut it down. I did during that time rev it and water shot out of the rear exhaust. Going through the overheating steps at SKIDIM this told me that the water pump was good. I decided to pull the thermostat myself and leave it out and check temp again. Started engine and temp never rose above 115F. WOW. This does tell me that I am getting water through the jackets doesn't it? I did this several times with the same result. Called the shop where the service was done and just so happen the tech who performed the service had to step out. Talked to the owner about what I had found and he verified that from what it sounds like the thermo is bad. As noted in my previous post the tech suggested that I have a machine shop pull the engine and clear the water jackets. He quoted me a price from someone he new at aroung $3,500 for the whole job.
I will be ordering a new thermostat tomorrow or might even go to Houston(75miles away) and pick one up myself. I could understand that the orginal thermostat was bad but he installed a new one(or so he said) and when I found out he put a 160F in instead of original 143F I had him change it out. It still overheated after all this.

[High altitude]

No overheat without the thermostat in means your system is fine. IMHO...ALWAYS suspect buffoonery from your service folks. Some are incredible, but many are borderline incompetent, and a few could be classified as downright thieves. I always do troubleshooting myself even if that means buying an extra part or two online. It is crazy what the shop charges for labor and most of this stuff is very basic if you have a logical mind and some mechanical ability. Once you get to the more modern engines, the electronic "brains" are so complicated that this theory doesn't always work out.

If you can wait a few days order the thermo from SKIDIM and ask if they can send it via USMail Priority. You wil receivce it in two to three days and save the gas it takes to go 150 miles round trip. If you are like me...sometimes you would just rather drive and get the part that day to see the results. With that in mind, you could probably go down to NAPA and get a 143 degree thermo. Even if you just use it as a tester (I think there is a subtle difference between the two, but I can't remember anymore) it might give you the peace of mind to then order the part and install it yourself. -Marc

[yellowMIL]

Are the gauges telling you that the motor is overheating or does the motor / water coming out feel like 200F. For a while on my 1990 my ground wire to the dash would act up…..
Also does the thermostat have a little hole for pass thru, just to let some water out….Already have hose connected, thermostat off , run more water thru it to get all the trash out.....

[tsassman]

I ordered a new 143F from SKIDIM today along with several other items and spoke extensively with Vince(great help). He indeed said it probably was a faulty thermo, but still could be a number of other things. I couldn't wait so I drove to Houston to pick one up from Palmer Power. I spoke a good long while with the manager there who also was very helpful. I showed him the old thermostat that I took out and he confirmed that it was a 160F. Remember in my previous post that when I found out the tech had installed a 160F I had him change it back out to the original 143F which he said he did. Obviously he LIED.
Well I got back home and immediately installed the new thermostat. Hooked up the water supply and started the boat the temp. rose to 140-150-160 all the while I had my hand on the top of the thermostat housing to see if I could tell a temp. change. At 165 I started to feel a difference, at 170 it stopped rising and dropped back down to 160 and stayed there. I let it run there at about 1,000 rpm for about 5 minutes feeling spots on the engine, checking water flow out the back. I felt safe to rev to about 1,500 with not much change. I decided to install my fresh water strainer back inline, had to go to local auto parts store to obtain new o-ring. I installed the strainer along with reconfiguring my water hookup. I this time used a 5 gallon bucket to let the water hose fill the bucket and let the motor pull the water from the bucket. With the bucket full and water running over I started the engine. Same result with the temps and felt good suction from the hose connected to the engine. At 1,000 rpm and water on all the way, the bucket would still run over. At about 1,500 the bucket would stay level with the top, at 2,000 the water level in the bucket starts to drop fairly quickly. I feel pretty confident I have solved the issue, but the true test will be getting it into the river(hopefully tomorrow evening, have to work). Another step I want to verify is test the engine areas with thermo gun(hopefull tomorrow or Thursday). On and by the way I still have yet to recieve a call back from the shop where the original service was done(imagine that).