Temperature/Overheating Problems?

[pgowdy13]

Hi, everyone,

I'm a second year owner of a 93 Sport Nautique with a 351 that I got a very good deal on. It's in beautiful shape! We ran it the entire Summer last year, and we had virtually zero problems with it.

I must say, I've been doing more and more and more reading on it and becoming in-tune with the boat. I've done some small procedures (replaced the steering cable, redid the ski-deck, winterized, etc.), but I'm by no means a mechanic, and most of the time I depend on the internet for instructions and such. Anyway, on to the problem...

Last year when we ran the boat (I live in Kansas), it was an incredibly hot summer with very hot water temperatures, and the boat would consistently run up to 200 degrees. Whenever it got up at that temperature I'd back off a little bit, and get it back down some, but it wasn't too uncommon that it would hit 200 degrees. In fact, at some points during the summer I think it went a bit over that.

This summer the first thing I did was replace the impeller before we took it out for a real proper boating session. Today I took it out for the first time, and there was a point that it hit 200 degrees after I had ran it at about 4100 RPMs for 30-40 seconds. It wasn't at all uncommon for the boat to be staying around 180 degrees either.

I guess my big question is... is this normal? From all of the reading I've been doing around here, I would conclude that it definitely isn't. What harm did I possibly do to the engine last summer if I ran it and it was having overheating troubles? What are "troubling" temperatures? If I continue to run it with it hitting 200 degrees, what kinds of problems would it cause? Also, what steps should I take to remedy the overheating problem? Is it possible the impeller was installed incorrectly? I'm just not sure what to think here. Thanks for any information!

[pgowdy13]

Here are some pictures of my baby, btw.

[LakeRats]

Since you replaced the impeller and still have problem, check temp gauge, check thermostat and then check circulating pump. If it is dripping water out of the bottom, may need to replace it. 200 is too high.

[hyparks]

Check all hose clips to make sure they are tight. Loose pipes can allow air to be sucked in, which can cause high temperatures. If you have a strainer check it's tight and check the seal between the 2 faces is still intact.

[Luke 'Lukey' Thomas]

Check for leaks, check the strainer. And an odd-ball, but check the voltage at the time your engine temp climbs up. Its possible your belts slipping, if it is the voltage drop should be a good tell tale.

[pgowdy13]

Check for leaks, check the strainer. And an odd-ball, but check the voltage at the time your engine temp climbs up. Its possible your belts slipping, if it is the voltage drop should be a good tell tale.

Thank you all for the advice so far!

What is a normal voltage to be running out on the lake? It's usually around 12.3 at cruising speed... 12 if I'm running the blower.

[TRBenj]

Youre likely to see a voltage drop to the dash even with a properly tightened belt. 80's and early 90's Correct Crafts were notorious for undersized wiring to the dash, compounded by old, dirty connections, and youre only likely to see 12v or so on the gauge (when it should be 14+). While not ideal, nothing is likely awry.

The alt and RWP also use separate belts on a PCM Ford, so even if you were seeing a low voltage condition due to belt slippage, it doesnt tell you diddly about the RWP.

You need to tell us a bit more about the nature of your overheat if you want us to narrow down where to look. Try this for us:
1. What temperature does the engine attempt to regulate to? 160? 180? Something else?
2. If you warm up the boat and then idle around for an extended period (5+ minutes), what happens to the temp?
3. If you maintain speed for an extended period (several minutes at 25-35mph), what happens to the temp?
4. If you come off plane and return to idle after performing #2, what happens to the temp?

Answer those questions for us and we can give you a pretty short list as to what is wrong.

[jbach]

all good info.

1. i'd replace the thermostat with new one of the right temperature to start. cheap $5 insurance. 143 degree i believe is right, but double check that. the EFI GT40 engine is a 160 stat.

2. i'd pull the rwp intake hose from the thru-hull and put it in a 5 gallon bucket and start the engine. it should suck it dry at idle in 10 or so seconds. shut it down before it does go dry. if it's longer than 15 seconds or so, engine is being water starved.

i just replaced my raw water pump due to failed bearings and seals. it will now suck a 5 gallon bucket faster than my hose can replace it. the old pump would not, even with a brand new impeller.

[pgowdy13]

Youre likely to see a voltage drop to the dash even with a properly tightened belt. 80's and early 90's Correct Crafts were notorious for undersized wiring to the dash, compounded by old, dirty connections, and youre only likely to see 12v or so on the gauge (when it should be 14+). While not ideal, nothing is likely awry.

The alt and RWP also use separate belts on a PCM Ford, so even if you were seeing a low voltage condition due to belt slippage, it doesnt tell you diddly about the RWP.

You need to tell us a bit more about the nature of your overheat if you want us to narrow down where to look. Try this for us:
1. What temperature does the engine attempt to regulate to? 160? 180? Something else?
2. If you warm up the boat and then idle around for an extended period (5+ minutes), what happens to the temp?
3. If you maintain speed for an extended period (several minutes at 25-35mph), what happens to the temp?
4. If you come off plane and return to idle after performing #2, what happens to the temp?

Answer those questions for us and we can give you a pretty short list as to what is wrong.

I'll do my best here with the memory of yesterday. I'll take it out this Friday and get a better idea of what exactly it does, and then I'll give you answers to the ones I don't know.

2. We actually idled around the dock for probably 10 minutes just looking around at other boat, and it seemed to hold at around 160 degrees. This was pretty consistent. In fact, anytime we were at a stop for an extended period of time the boat seemed to hover at around 160. The only exception to this was when we had been running the boat pretty hard while cruising (32-34 mph) and then we would stop. It took FOREVER to get the temperature back down to 160. At one point I cruised for 30 or so seconds at around 38-39 MPH, and this is when the temperature flared up to 200 degrees. When I saw it that high, I let off a bunch.

I'll try to answer the other questions in more depth in a few days . I hope this helps so far. I'll definitely go around and tighten all the belts, check the strainer, etc.

[pgowdy13]

all good info.

1. i'd replace the thermostat with new one of the right temperature to start. cheap $5 insurance. 143 degree i believe is right, but double check that. the EFI GT40 engine is a 160 stat.

2. i'd pull the rwp intake hose from the thru-hull and put it in a 5 gallon bucket and start the engine. it should suck it dry at idle in 10 or so seconds. shut it down before it does go dry. if it's longer than 15 seconds or so, engine is being water starved.

i just replaced my raw water pump due to failed bearings and seals. it will now suck a 5 gallon bucket faster than my hose can replace it. the old pump would not, even with a brand new impeller.

Yes. 143 is correct. I went ahead and ordered the thermostat just now.

[TRBenj]

Do finish the prescribed checks, but that gives us a good idea where to start.

Regulating temp at 160 means you have the correct thermostat (143) in there. Sounds like you are overheating at speed and cooling down at idle. This would eliminate an air leak between the RWP and pick up as a major contributor.

Overheating at speed usually indicates one of a few things. Bad impeller, blockage in the cooling system, or a RWP in need of a rebuild (pulling air past the seals). What brand of impeller did you install this year? What was the condition of the old one you removed? I would pull the hoses that go to the front of the 2 exhaust manifolds, as well as the thermostat housing, to see if there are any blockages in there.

[pgowdy13]

Hello again, everyone!

Today I installed the new thermostat, and I think it went pretty well. I've never really dealt with anything like that, and I've never put on a gasket, so I hope everything went okay. Here are some pictures of the Thermostat Housing and the Raw Water Strainer along with the old Thermostat. In my opinion (and that really doesn't count for much when it comes to mechanics) it looks quite corroded and old. I'm not sure if this is how it's supposed to look, but I went ahead and cleaned the housing with a putty knife and rubbing alcohol to make sure I got off all of the old gasket and any material left over from corrosion.

I also tightened every single belt on the engine and made sure it was very snug.

I took the hoses off of the Raw Water Strainer and checked to see if there was anything I could see. If you actually want to open the Raw Water Strainer, do you just screw it off. It seemed like it was threaded, but I applied quite a bit of force to turning it and could not get it to loosen, and I'm a pretty strong guy. I'm not exactly sure what tool I'd use to separate the actual Filter from the housing. The picture I included shows the only bit of goop I could find around the strainer, and it clearly seems to be adhering to the plastic instead of to the filter. Besides that it looks perfectly clean from the outside. Should I go ahead and try to get it opened?

I have two more questions:

1. Thinking back to the Impeller installation, I know for sure that it was a very tight fit. I had to bend the feet a bit to get it to fit in (and that's how the old one looked to be installed as well). I bent the feet the same way the old one had been bent (which I assume is opposite the direction of rotation). I might go ahead and take the pulley off, take a picture, and post it on here so you guys can assess whether or not I installed it correctly. As far as the old Impeller, it looked wonderful. So good, in fact, that I debated just leaving it and saving the Impeller I bought for next year. This is the impeller I bought (I emailed the parts dealer first and asked which one I needed) http://www.nautiqueparts.com/sherwoodimpellerkit.aspx.

2. My girlfriend and I lost the original boat key and our copies aren't working. I'm going to have to pull the ignition out and take it into a locksmith to get a new one made. I've assessed the difficulty of this, and it doesn't look like it will be too hard. Is there anything special I should keep in mind? I've taken about 8 pictures from different angles documenting the wiring so I can reconnect it correctly. Is it as easy as removing the dash screws, removing the 4 screws for the ignition panel, detaching the three wires in back, and pulling it out? Any input on this would be great!

Well, that's all I have so far, thanks again for the advice so far .

[LakeRats]

Lost key - just buy a new ignition switch. Probably cheaper than getting a new key made. Strainers can be very difficult to unscrew. Have seen them broken in the process of trying to unscrew. Have you run it since the thermostat change?

[pgowdy13]

Lost key - just buy a new ignition switch. Probably cheaper than getting a new key made. Strainers can be very difficult to unscrew. Have seen them broken in the process of trying to unscrew. Have you run it since the thermostat change?

The locksmith in town is really good and he said it'd "be 15 or 20 bucks if you bring the ignition in." So I think I'm just going to do that.

In regards to the strainer, YES! I was not able to unscrew it, and at this point I don't want to risk breaking it. Any tricks for getting the thing apart?

I have not run it since I put the new thermostat in. My gf and I will run it later this week... possibly on Sunday, and I'll report back with the results! Thanks again!

[pgowdy13]

I got 4 keys made off of the lock, and the total was 8 dollars. They are all in confirmed working order this time. I'll never again go to ACE for getting keys cut.

This morning before I pulled the ignition, I went ahead and a pulley off so I could take pictures of how I installed the Impeller. I also took pictures of the hoses that I checked for blockage.

The following is a list of numbers that correspond to the order of the pictures:

1. Picture is a far away shot of the way the "feet" of the impeller had to be bent in order to fit with respect to the rest of the housing.
2. This picture gives perspective to the way the housing for the impeller in installed and hopefully gives context to which way the pulley would be turning.
3. Another picture of where the impeller should be installed.
4. A very close up picture how the impeller and how the "feet" are bent.
5. Putting the pulley back on.
6. This is the first hose that I took off and checked for blockage. If you're looking at the engine straight on, it's on the right side and attached to the thermostat.
7. I also took these two hoses off and checked for blockage. Note that I did this while the impeller was off. That is why the bottom hose is not connected to anything.

Sorry for my noobishness in all of this. I just want to make sure I'm doing the work properly. Thanks!