gt 40 cooling issue
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=33986
Printed Date: October-08-2024 at 11:02am
Topic: gt 40 cooling issue
Posted By: tjca77
Subject: gt 40 cooling issue
Date Posted: June-27-2014 at 12:38am
| Boat is a 2000 Air nautique, with a gt 40 in it. At the lake this week and just got the wife comfortable pulling me. Well, this morning after a quick set on the slalom, she picks me up and she gets ready to wakeboarding, I go to start up the boat and the temp is running hot, around 190. Engine first start right away, so, but when it does the raw water colls things down to 160, 165 right away. We decide to head back to the dock. The boat runs fine for 15 minutes at 25mph and 5 minutes idling back. I pulled the raw water strainer and cleaned out some junk, mud, and small debris, then tested it by running it like you would pull a slalom skier, quick acceleration to @ 34, then stopping to pick up, and killing the engine, couldn't recreate issue so we head back out to do a little wakeboarding. Wife goes for 10 minutes and temp rises to 175 when she stops. No issue cranking it back up again. We drove back to the dock with no heat issues at all. I am concerned there is a problem running the engine under load and would appreciate any suggestions. |
Replies:
Posted By: MrMcD
Date Posted: June-27-2014 at 5:45am
|
I just went through a similar issue with my 95 GT40. I did not wish to chase issues all summer so I replaced the impeller and O ring plus sealed the plate with new gaskets. Installed a new Thermostat then pulled my strainer and inspected it and the sealer ring. I used a synthetic grease on the threads of the strainer before screwing it back together, synthetic grease is supposed to be safe with the rubber gasket. Next I checked all connections of the hoses from the raw water pick up all the way, checked the trans oil cooler clamps and the clamps at the raw water pump. I can't say exactly which fixed mine but I am happy to report the temp is steady at 160 now regardless of the task. I was able to tighten several of the clamps. You may wish to use a hair dryer to warm the hoses at each connection before tightening. A warm hose will conform better than a cold hose and you will seal it better. Any intake hose air leak will cause your raw water pump to pull air along with water and you will get heating issues, normally at lower RPM levels. I first noticed my heating issue when the engine cut power on acceleration, I suspect the computer was warning me to check my gauges and cool off the engine. I never exceeded 190 that I know of. |
Posted By: TRBenj
Date Posted: June-27-2014 at 7:38am
| Are you worried that your temps rise after shutting down? Because that is normal. Especially after running hard. There is no cooling water being circulated while the engine is off, remember. So long as it cools back down upon restarting, you're fine. It's not overheating while running, is it? |
Posted By: tjca77
Date Posted: June-27-2014 at 10:22am
|
No, it stays at 160, or 165 while running no issue with any rise in temp while underway. This goes for idle and at speed. When I shut it down after running it pretty hard then turned it back on is when I saw the temp jump. After I started it back up, the temp quickly dropped from @ 190 , maybe a little less, to 160. Wasn't sure if this was normal or if there is an issue. I will go through the hoses this morning and check for tightness after we run it, but maybe I am chasing a ghost??? This is my first inboard, correct craft, ect, so I don't have a great handle on normal behavior. Thanks for the help. |
Posted By: Hollywood
Date Posted: June-27-2014 at 12:38pm
|
No issue at all, that's normal. ------------- |
Posted By: Gary S
Date Posted: June-27-2014 at 2:01pm
|
Your most likely used to modern automotive gauges that don't do that and are comparing that to your boat. I don't know if their dampened or they are not much more than an idiot light. My MG water temp gauge uses a capillary tube gauge filled with either that is always "on". Without it even running you can see the tempature changes of the day,it is that sensitive. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: tjca77
Date Posted: June-27-2014 at 2:31pm
| Went through all the hose clamps I could get my hands on, nothing more than a turn or two. Had the boat out this morning for a ride, temp never moved. We didn't ski, wind had the lake chopped up. Is it best to keep the boat in neutral while picking up a skier? You are right I am not used to seeing the temp fluctuations, just don't want to mess anything up. Thanks for the help. |
Posted By: Bri892001
Date Posted: June-27-2014 at 2:54pm
|
It's a good idea to check the tranny cooler for any debri that might make it past the strainer. Check the strainer of course, and it's good to note when the last time the impeller was changed, and if you have no idea, think about changing it as a matter of general maintenance. That said, what you're seeing is totally normal and is called "heat soak." It's basically because the flow of water has stopped. You mean keep the boat in neutral (and running) while picking up a skier? I'd say it's better to shut if off when you have people around the platform, especially any kids. I tend to like to idle back to my skier after a hard run (instead of going back fast and cutting it all of a sudden), to give it a moment to cool. That's just personal preference though, not a necessity. |
Posted By: tjca77
Date Posted: June-28-2014 at 12:14am
|
Thanks for the help. Was able to ski a little this afternoon, and saw the temp move to 180 then back down after starting back up. Have another question, what is the max temp this should spike to without hurting anything? The new impeller just got bumped up, been meaning to do, it since May. I have service records on the boat and the last impeller was changed out about 1 year ago. Not sure how many hours between the time though. The strainer is nice and clean. Where is the transmission cooler? I would like to check that out as well. |
Posted By: SNobsessed
Date Posted: June-28-2014 at 12:26am
|
Follow the raw water line from the strainer towards the engine. Mine is on port aft side of engine. ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: JLags
Date Posted: June-30-2014 at 10:30am
| I have a similar issue, that's driving me crazy. My 96 Sport Nautique GT40 use to run 160 at idle or at any rpm. Now at 2500 rpm or higher it's about 165-170 and at idle will creep up to 190 fast. I'm at a loss, I have replaced the raw water impeller, checked and tighten all hoses, cleaned the transmission cooler, replaced the strainer gasket. The old impeller was not damaged so suspect there are no stray parts in the manifolds. Also since this issue developed there and allot more steam I mean allot! What's next new thermostat or just replace the whole water pump? I'm stumped on this one. |
Posted By: Bri892001
Date Posted: June-30-2014 at 12:37pm
|
When you're creeping up to 190 at idle, what does the old "put your hand on the Exhaust Riser test" tell you. Is it warm, or scalding hot? If it's just warm, you're getting good overall waterflow and that would point towards a thermostat. If it's closer to scalding hot, then we've got to look for some sort of flow problem. Blockage or air leak. Also, when you were tightening everything, make sure you didn't squash your tranny cooler with the hose clamps. It's happened before. |
Posted By: Hollywood
Date Posted: June-30-2014 at 12:46pm
That's from prying the hose off with a screwdriver, not the hose clamp. An impeller can last hundreds of hours if kept wet and you can fry a brand new one in less than a minute.. ------------- |
Bri892001 wrote:Posted By: Bri892001
Date Posted: June-30-2014 at 12:53pm
^^Ahhh, that makes more sense. |
Posted By: Hollywood
Date Posted: June-30-2014 at 12:55pm
|
^^^ and there is usually a nice long scratch down the middle of the dent. ------------- |
Posted By: JLags
Date Posted: June-30-2014 at 2:26pm
| Thanks for the reply. They feel hot to me(can't keep my hand on them) but I can't say I ever felt them when it was running normal. Makes me worry something is blocking the flow, seems kinda strange. I don't see how anything could get past the transmission cooler and strainer. Should I be looking at the manifold? One is original, the other replaced because a bolt broke when the gaskets where changed. |
Posted By: Bri892001
Date Posted: June-30-2014 at 3:11pm
|
Do you have one of those quick flush connections installed? Sometimes that's a source of air leak. You're best bet is to perform the "Bucket Test." You'd get some good examples of how to do that if you google correctcraftfan bucket test. As far as obstructions, you'd have to take each section of the cooling chain apart, hose by hose, and see if you've got anything blocking. I wouldn't suspect the manifold itself though. |
Posted By: JLags
Date Posted: June-30-2014 at 3:32pm
| No quick connect installed for flushing. I guess I need to complete the bucket test. |
Posted By: Hollywood
Date Posted: June-30-2014 at 3:56pm
|
Since this is a new issue, I'd have to say it's due to an improper winter/summerization. However, since there has been someone monkeying with the exhaust do verify the gasket is on proper. Water flowing to the underside of the riser should be blocked by the gasket. This forces cooling up to the top of the riser. There is really only 1 manifold, it doesn't know which way is forwards. There water outlets on both sides so it can be installed on either side of the engine. This makes gasket orientation key. The tab on the gasket should match the tab on the riser. It won't make a difference on your temperature gauge, but you will have a warm riser and excessive steam, possibly leading to a hose failure. Our Martinique was kindly delivered this way...   *Don't ask me why there is a water inlet on underside of the riser. It could be a 2 piece core in the casting process, which would simplify the amount and orientation of them in the mold. Or there could be other applications with increased water flow that utilize all sides. ------------- |
Posted By: wheels06
Date Posted: July-01-2014 at 1:10am
| I am having the same issue. I have a 96 Sport Nautique, replaced the impeller last year, no water leaks that I can see and when I'm running at 10mph the engine cools right down. At an idle(once the engine is warmed up) it starts heading to 190 quickly. Goes back down as soon as I hit the throttle. I checked the strainer, it was clean. I pulled a hose on top while it was running and it was pumping, although I thought it should be a little more than it was. |
Posted By: Bri892001
Date Posted: July-01-2014 at 9:29am
| John, did the problem exist before you changed the impeller? |
Posted By: JLags
Date Posted: July-01-2014 at 12:35pm
|
Okay I did the bucket test it takes about a min to pump a 5 gallon bucket full of water. I also connected longer hose to the raw water pump intake to take water directly from the bucket to bypass the strainer and potential clogs. The result was the same draws very little water still warms up to 190 at idle. Can someone tell me if the pump is installed correctly. I have never switched the direction but it doesn't look correct after all the images I've seen. 
|
Posted By: Bri892001
Date Posted: July-01-2014 at 12:43pm
|
Did it ever cool correctly with the pump oriented that way? That is one potential mistake that can be made. That pump is designed to work with a lefty or a right hand rotation motor, but the pump is turned depending on what you have. The little set screw, is the indicator. Did you install that skinny O gasket on the pump when you replaced the impeller? Are you using a PCM or Sherwood Impeller, or are you using an off brand like Sierra? |
Posted By: JLags
Date Posted: July-01-2014 at 12:49pm
| Yes it use to cool fine, the previous owner did replace the pump before I purchased it about 4 years ago. There is a Sherwood tag on the the pump. I put in a PCM Impeller and new gasket when I replaced it. I don't see any water leaks around the pump. The whole seems odd to me, I thought if the pump was in wrong there would be no water and overheat at all RPMs. |
Posted By: Bri892001
Date Posted: July-01-2014 at 1:00pm
|
So, when did the overheating start, place the following in the correct order, sorry if these seems like a silly exercise, just trying to get my head around it: -Pump was replaced by previous owner -You bought the boat -Exhaust manifold replaced (probably not relevant but just in case) -You replaced the impeller -You noticed the overheat |
Posted By: Hollywood
Date Posted: July-01-2014 at 1:11pm
|
The pump is correct for your engine. The hoses should be tucked close to the block for Left hand rotation. It would overheat immediately if it was on backwards. ------------- |
Posted By: JLags
Date Posted: July-01-2014 at 1:13pm
|
Timeline in the correct order. -Pump was replaced by previous owner -You bought the boat -Exhaust manifold replaced (probably not relevant but just in case) -You noticed the overheat - I noticed the excessive steam too -You replaced the impeller |
Posted By: MrMcD
Date Posted: July-01-2014 at 2:41pm
|
Your leak may be the intake hose itself. A crack or tear, any leak path that will allow air to suck in rather than water. Can you try the bucket test with a new hose? Sometimes these hoses are as old as the boat and they crack. The only way I can think of to test the hose would be to pressurize it. Plug one end and clamp a garden hose in the other end and turn on the water. If properly sealed you should see no leaks from garden hose pressure. |
Posted By: JLags
Date Posted: July-01-2014 at 2:56pm
I wish it was that simple as a hose! I used another hose I had the same diameter for the bucket test that is new. 
|
Posted By: Bri892001
Date Posted: July-01-2014 at 3:30pm
|
Given the order of events maybe the manifold, or some hose or fitting associated with it, is in fact relevant. I would remove the hose going to your new manifold, but not on the manifold side, on the t-stat side. Now, try to blow through the hose, so your blowing through the coolant passage in the manifold. I have to admit, I've never done this, so I don't know how much resistance to expect. But, I'd think you'd know if there's excessive back pressure. All of the water eventually needs to escape through the exhaust manfifolds, so if it can't escape for some reason, everything is going to overheat. |
Posted By: MrMcD
Date Posted: July-01-2014 at 3:39pm
|
Take the thermostat out and test with no thermostat. Sounds like restriction for sure. It the restriction is not in the thermostat start flushing. Maybe back flush the hoses and block, see what you get out of it. Could be a large chunk of a previously failed impeller coming back to haunt you. |
Posted By: MrMcD
Date Posted: July-01-2014 at 3:45pm
| If none of the above solves your heating issue the engine water pump may be suspect. I have seen the impeller on some pumps rust away till it is ineffective and I have seen the impeller lose its clamp on the shaft and free spin rather than pump water. Rare and the last thing I would check but possible. |
Posted By: Hollywood
Date Posted: July-01-2014 at 4:36pm
|
A blocked thermostat would give you cool risers. Everyone wants to change thermostats but they rarely go bad. Like you said though, you can test it and also run without. ------------- |
Posted By: wheels06
Date Posted: July-02-2014 at 5:00pm
| Yes it did, that was why i changed it last year. I was hoping it solved the issue. |
Posted By: wheels06
Date Posted: July-02-2014 at 10:07pm
| my apologies, my previous post was to the question of whether this issue existed before I replaced the impeller last yr. I just took the water pump off and noticed something. There was a post earlier, "the set screw is the key"...what do you mean by that? Mine is facing towards the engine. Is that correct? I have a Sherwood. Looking into the pump the impeller seems to be fine. I'll be checking hoses next. This is very frustrating given the weekend coming up. |
Posted By: Bri892001
Date Posted: July-02-2014 at 10:48pm
|
John, There's three different overheating at idle boats going concurrently in this thread, so it's easy to lose track. The set screw indicates which way the pump is facing. Per Hollywood, in is correct for a Left Hand Standard (Most GT-40s are) engine. Also, you'd be overheating at every rpm if it was faced wrong. 1.) Yours if fine anywhere but idle, right? 2.) Was there anything changed etc. before the overheat? 3.) If yours is getting hot at idle, 190ish, are the exhaust manifolds too hot to put your hands on, or is this just a gauge indicated overheat? 4.) You replaced the impeller: A.) Did you correctly position the thin o-ring B.) Did the kit come with a paper gasket and if so did you put it in (shouldn't reallymatter, but just wondering C.) Did you use a PCM or Sherwood impeller or an off-brand? 5.) Do you have a quick flush kit installed anywhere 6.) Did you check your strainer for blockage and presence of gasket? 7.) Did you check your tranny cooler for blockage, end crushage? Hose clamp snuggness? 8.) Any other gauges giving wonky indications? |
Posted By: wheels06
Date Posted: July-02-2014 at 11:25pm
|
Bri892001, 1. Correct 2. No 3. it's too hot to put my hand on, not just the gauge. 4. Impeller was done correctly with a PCM. It didn't have a paper gasket, but I made one. There is no leakage from pump. 5. No quick flush kit that I can tell. 6. BINGO! Gasket is missing. Just called "local" dealer...30 miles away. They open at 10 and I'll be there at open and they have them in stock. 7. No, I didn't see anything that would be a problem. 8. All gauges are working fine. I can't thank you enough for your advice! This site is great for advice! I'll update results tomorrow! Thanks again! |
Posted By: Bri892001
Date Posted: July-03-2014 at 12:04am
|
Nice! Keep us posted. |
Posted By: Hollywood
Date Posted: July-03-2014 at 2:48am
|
You might as well look in the bilge for that gasket. You can get two 10 packs of them from McMaster for the price of one PCM from a dealer. ------------- |
Posted By: MrMcD
Date Posted: July-03-2014 at 6:01am
|
I made a silicone gasket for my 78 Nautique, it worked for years. I filled the Oring slot with silicone, coated my cover with light grease where it would be touching the silicone. Installed the cover and let it dry. The cover still came off normally because the grease kept it from sticking closed. I used that gasket for years. I think your lack of gasket created your issue. A minor air leak will give all of the symptoms you mentioned. Congratulations on a cheap fix although you had several headaches first. |
Posted By: MrMcD
Date Posted: July-03-2014 at 6:05am
| If your strainer is like mine, 95 GT40 Engine, a little synthetic grease on the threads will make installation much easier. The plastic on plastic threads are sticky and it is hard to tell when the strainer is actually tight or if you are just fighting sticky threads. |
Posted By: MrMcD
Date Posted: July-03-2014 at 1:53pm
| Hollywood, would you happen to have a part number for the McMaster source on the seals? Maybe what years it would cover? Thanks |
Posted By: Hollywood
Date Posted: July-03-2014 at 2:27pm
|
9875K29. Same diameter canister, and therefore gasket, for the 1.25" big block strainer as well. $8.78 for 10. I layed one of these over a PCM just last night and couldn't tell the difference. I also grease my threads, have come across some very stiff & sticky strainers. I typically boat in clean enough water to not need one but have been too lazy to cut a new hose from the hull to the trans cooler. ------------- |
Posted By: MrMcD
Date Posted: July-03-2014 at 9:54pm
| Thanks for the part number, my GT 40 has the gasket that looks like it came off an oil filter. Both my Nautiques have run a water filter/strainer. They do catch leaves and things all the time. My Malibu had no strainer on the intake water line. I guess all the leaves just end up in the block or go out the exhaust? |
Posted By: Gary S
Date Posted: July-03-2014 at 11:09pm
|
Usually Mark they get caught in the trans cooler ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: Bri892001
Date Posted: July-04-2014 at 1:05am
|
If I was fighting a frustrating issue for a long time and I could fix it for under ten bucks before a summer holiday weekend, I'd be very happy man, even if said part could be had a little cheaper elsewhere. So, did the original poster get his gasket and go skiing or what? |
Posted By: JLags
Date Posted: July-06-2014 at 12:36am
So long story short, a new raw water pump did the trick. No more issues overheating even at idle  There is still a bit more steam than it use to have but it seems to fine. Thank you everyone for helping.
|