Boats For Sale:
Cooling System Troubleshooting |
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Whitefish1989 
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Joined: June-14-2023 Location: MN Status: Offline Points: 9 |
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 Topic: Cooling System TroubleshootingPosted: June-17-2023 at 11:01am |
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New to the forum here - hoping to get a little help. Have a 1989 Nautique w/ the PCM Ford 351 engine. Boat was layed up for about 5 years in storage. Winterized it before it went into storage including filling the cooling system with RV fluid. Took it out of storage this year, swapped out the gas, oil and oil filter and it started up beautifully but the temp gauge immediately showed it wasn't cooling. Ran right through 160 to 200 so never left the dock. The filters are clear, the pump rotates and seems to be pulling water (when I shut down the engine I can hear water gurgling out of the exhaust system) but it is not cooling properly. Pulled the hose and tried looking at the impeller and it looked OK as best I could tell. Need some suggestions on what direction to go.
The manual seems to imply there are two pumps? a "flexible impeller supply pump" and a "high volume circulation pump"? or are those one in the same. Also curious about the "thermostat that controls the discharge" - where is that located? Thanks
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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Posted: June-17-2023 at 5:43pm |
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You really should pull the impeller out of the pump to see what kind of condition it's in.
 You have both pumps that you mention and the thermostat is at the front top of the engine in the housing in front of your distributor. Remove the 3 hoses from the cover, and there are 2 allen headed bolts holding the cover down, remove them and pull the cover off and you'll see the thermostat. There are other things to check but this should keep you busy for a while and you might find the problem You should also check all the hoses and their clamps on the suction side of the pump to make sure you don't have a path for air to leak in, since the suction side is operating at a vacuum |
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Tim D
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Joined: August-23-2004 Location: United States Status: Offline Points: 2635 |
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Posted: June-18-2023 at 8:48am |
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The impellor should be replaced. 5 years sitting, when was it replaced before the storage? I would say it's hard and lost flexibility, where it needs to bend over the cam inside. Hopefully you haven't lost any blades in the block.
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Tim D
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Whitefish1989
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Joined: June-14-2023 Location: MN Status: Offline Points: 9 |
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Posted: June-19-2023 at 12:22pm |
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Thanks for the advice. All sounds like good information. Unsure of the impeller age so I will just replace it as it sounds like these are known weak link in the system. If I have to move on to the thermostat - once I access it how do you typically troubleshoot it?
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Jonny Quest
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Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2846 |
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Posted: June-19-2023 at 9:07pm |
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I used to replace the impeller every year...now it's every 2-years. Cheap "insurance" and peace of mind.
JQ
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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Morfoot
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Joined: February-06-2004 Location: South Lanier Status: Offline Points: 5311 |
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Posted: June-20-2023 at 6:16am |
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When you pull the impeller Make sure all the vanes are there. If you have some missing, then you'll need to go "Fishing" for the missing pieces. Thermostat is easy. Remove and inspect it and if you wanna test it then get a pan of extremely hot water and place the thermostat in it. Ideally if you have the means to measure the temp of the water then you want it to be around 150-170' F. T-Stat should be a 140'F so if you drop it in your pan of hot water... It should open. If it doesn't then obviously it's bad.
My money is on a bad impeller. 5 years old then it's lost it's flexibility.
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"Morfoot; He can ski. He can wakeboard.He can cook chicken.He can create his own self-named beverage, & can also apparently fly. A man of many talents."72 Mustang "Kermit",88 SN Miss Scarlett, 99 SN "Sherman"
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cbr1000dude
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Joined: August-23-2011 Status: Offline Points: 330 |
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Posted: June-21-2023 at 6:19pm |
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Whle you have the hoses off, look at the brass L shaped fittings leading into the exhaust risers to make sure they are not clogged.. See my "Kaboom" post.
Impeller is too old also. Welcome to CCFan, lots of good info and helpful people here.
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Whitefish1989
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Posted: July-03-2023 at 2:06pm |
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Amen to all the helpful advice. So I swapped out the impeller as suggested and checked all the hose clamps upstream of the cooling pump for tightness. Now when I run the motor the temp gauge seems to top out at 185. Never really goes above that even after running for 10-15 minutes. Haven't tried to run it longer. So what is the next move? 185 seems a little hot from what I have read but it is apparently cooling. Holding off on checking the thermostat because I don't think it has ever been opened and it looks like it could be a bugger to crack open. Looks fused....even seems to have the original factory silver paint intact. Just want to make sure faulty thermostat is consistent with running hot but not endlessly hot.
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KENO
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Posted: July-03-2023 at 8:13pm |
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If it's never been opened................then it's time.
You never know what kind of treasures you might find in there Broken impeller parts from sometime in the last 43 years, chunky rust flakes from corroded cast iron blocking some flow come to mind. |
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Whitefish1989
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Posted: July-16-2023 at 12:34pm |
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Well - here is one more twist to the story. I stumbled into a post on another site that suggested gauges don't always read right and the quick fix is to power up the running lights for a second as that puts a draw on the electrical system. And sure enough all of the gauges hit their pegs for millisecond when the light is switched on - and then they return to reading. Guess what now the operating temp is right on 160 and holding. So am I safe to assume the gauge was the issue. I have seen suggestions to use an IR thermometer to check the block temperature - anyone done this?
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KENO
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Posted: July-16-2023 at 7:01pm |
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If your gauges all do that, it means you have electrical issues that you'll be needing to resolve eventually.
Bad grounds, low voltage to the dash, corrosion in connections, loose connections all come to mind The gauge isn't your issue, it's just pointing out a bigger issue with your wiring that shows itself when you put more load on the dash wiring with the lights. Otherwise no comment on the "fix" from somewhere. Let's just say that most people end up with an IR thermometer in their tool collection for times like this and so should you. Aim it right at the temperature sending unit (front of engine on the intake manifold behind the thermostat housing, it should have a tan wire hooked to it)
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