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2002 GT40 running at 178 |
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Tbarile 
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Joined: May-10-2020 Location: Indiana Status: Offline Points: 55 |
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 Topic: 2002 GT40 running at 178Posted: June-12-2020 at 2:21pm |
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We just bought a 2002 196 with the GT40 in it. The thermostat was bad (corroded) and wouldn't open or close all the way so I replaced it (the temp with old thermostat was 120). I got a new one from Nautique parts. The boat now idles at 160 but climbs to 178 at running speeds. I've checked for air leaks, taken off all the hoses to check for blockages, etc.. The only thing I can find is the first brass fitting coming in from raw water intake is loose. It's going to be a pain in the butt to take that apart so I'm checking all options before doing that. Any other suggestions?
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Tbarile
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Joined: May-10-2020 Location: Indiana Status: Offline Points: 55 |
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Posted: June-12-2020 at 2:34pm |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3735 |
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Posted: June-12-2020 at 2:46pm |
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Which part is loose. Your arrow seems to point at the 45* elbow. I have not worked on a 2002 model year but your boat has a ball check valve above your arrow and currently it is about 70% closed. Why is the valve in the boat? The early boats don’t have one.
Open the valve 100% and your issue may go away. Push the lever down so it is in line with the intake hose to open. A couple of plumbing pipe wrenches would be used to tighten the fitting. Mark |
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Tbarile
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Posted: June-12-2020 at 3:13pm |
Yes, its the elbow. It's loose on the hull side, not the top that runs to RW strainer. The valve is factory, they were installed so you could shut off the water supply in an emergency. Not sure when you would want that to happen!! The valve is open all the way. I may have moved it when I was looking for the leak. Unfortunately you can't tighten it while its in the boat. When you turn to tighten, the other fittings hit the engine before you can turn it tight. I think you have to use some type of thread sealant to hold elbow at angle you need it to be at. |
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C_Heath
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Joined: January-21-2020 Location: NC Status: Offline Points: 207 |
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Posted: June-12-2020 at 3:26pm |
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Impeller? waterpump? belt within spec? 1/4 play both ways
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1979 Calipso Runabout (the boat that got it all started)
1988 Mastercraft ProStar 190 (sold) 2000 Pro Air Nautique/GT40 |
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slmskrs
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Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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Posted: June-12-2020 at 3:32pm |
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I'm surprised that they previously had a 120 thermostat in it. Is it possible the PO put a 120 in? It's been 160 (at least from 1996). You must have a digital gauge, but maybe your new thermostat opens a little later. Before you replaced the stuck 120, I assume the engine never got to normal operating temperature (meaning you have good flow into the engine). I have an analog gauge, but there is some fluctuation in temps.
I assume you have a new impeller in the raw water pump. |
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Gordon '97 Ski Nautique, GT40
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Tbarile
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Posted: June-12-2020 at 3:40pm |
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I put new impeller in. Could be water pump. Not sure how I would diagnose. Belts seem correct.
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8122pbrainard
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Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Posted: June-12-2020 at 3:45pm |
Todd, You''ll need to remove some fittings on top of the 45 elbow so you can swing it to tighten it up. For pipe sealant, I suggest Tru-Blue by Rectorseal or Blue Monster. Both are semi hardening and vibration resistant. Don't use Teflon pipe tape as it's too slippery and my not keep the pipe fittings in position. |
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Tbarile
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Posted: June-12-2020 at 3:46pm |
They had the correct thermostat, It was just so badly corroded that it wasn't working correctly. My boat has the analog temp gauge. 
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Tbarile
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Posted: June-12-2020 at 3:47pm |
I guess if anything my belts may be a hair too tight. Would that cause it? |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3735 |
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Posted: June-12-2020 at 8:58pm |
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No
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3735 |
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Posted: June-12-2020 at 9:01pm |
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Maybe the previous owner had a impeller failure and did not get all the rubber chunks out causing blockages in your cooling system. It has happened to others many times.
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Tbarile
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Posted: June-15-2020 at 4:13pm |
I pulled off all the hoses after impeller and couldn't find any pieces. Anyone know how you test a water pump? Most seem to think it's that first brass fitting coming up from the thru hull because it runs at 160 until we get up to 20+mph. |
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slmskrs
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Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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Posted: June-15-2020 at 5:00pm |
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A quick test of your pump/ impeller is to start it up when cold and put your hand on the back/side housing of the raw water pump. If it starts to get warm, water is not flowing sufficiently (air getting sucked in poor/old impeller, etc.). The pump housings should stay cool if lake water is flowing through it properly.
I do this test every time I replace the impeller. I know within a few seconds if it is pumping water correctly because it heats up very quickly with the rubber rubbing on the inside of the housing without water. |
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Gordon '97 Ski Nautique, GT40
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8122pbrainard
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Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Posted: June-15-2020 at 5:30pm |
Todd, Take a look at the RWP bucket test thread |
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MrMcD wrote: