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79 SN fouled thermostat housing |
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john_sn 
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Joined: August-02-2021 Location: Meridian, MS Status: Offline Points: 27 |
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 Topic: 79 SN fouled thermostat housingPosted: September-11-2021 at 7:16pm |
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Hey all, The engine on my 79 Ski Nautique has been running hot. It sits at ~180 when it should be 143*. I took off the thermostat housing to replace the thermostat and saw this:    Is this something I can clean, buy new gaskets for, and reinstall, or am I looking at a bigger problem? Im worried that if that's what the inside of the thermostat housing looks like I can only imagine how it looks inside the engine and exhaust housing. John |
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gun-driver
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Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
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Posted: September-11-2021 at 7:46pm |
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I would soak it in some muratic acid and scrub it out, then clean up the mating surface with a flat bastard file if needed. New stat and gaskets and give her a try.
The top housings are NLA unless you want to by a remaned one for ovr 200 bucks.😬 |
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Gary S
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Posted: September-11-2021 at 8:45pm |
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And don't leave in overnight either while in the acid- keep your eye on it
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gun-driver
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Posted: September-11-2021 at 9:21pm |
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^^^
Yes what he said, don't try to make it look new just soak it a little to clean it up. |
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swilliams
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Joined: June-26-2016 Location: Cincinnati,Ohio Status: Offline Points: 236 |
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Posted: September-11-2021 at 9:26pm |
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Being that rusty and crusty I would look further if the t-stat doesn’t help.
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1976 Martinique,350 Omc. 1975 Glastron/Carlson CV16,115 Merc.
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Gary S
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Posted: September-11-2021 at 9:36pm |
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+1 it's very possible the exhausts look the same or worse since they run at a higher temp. If the thermostat and housing refurbishment does not help the manifold and risers could use the same treatment.
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john_sn
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Posted: September-12-2021 at 12:37am |
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Ok, great. I'll try cleaning with muriatic acid tomorrow morning and see how it goes. I'll report back. Thanks! John
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KENO
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Posted: September-12-2021 at 6:31am |
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Those pictures pretty much explain why most marine engine rebuilders don't want your core shipped back to them. The whole engine including the exhaust manifolds and risers probably has the same issue. It can run for a long time with that corrosion though. I think somebody had a fetish for multiple colors of RTV and liked to use lots of it too  You might be cleaning out big corn flake looking pieces from the engine drains and exhaust manifold drains
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67 ski nat
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Joined: July-19-2018 Location: Santa rosa Status: Offline Points: 1194 |
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Posted: September-12-2021 at 8:35am |
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I use phosphoric acid (concrete prep or naval gel) Home Depot
Is muratic gentler or safer |
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gun-driver
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Posted: September-12-2021 at 12:30pm |
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I’m surprised you can even buy that stuff in Ca. To answer your question NO.
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john_sn
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Posted: September-12-2021 at 4:47pm |
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I went at it with muritatic acid, a brush, steel wool, and a file for a couple of hours, and made a little progress but not much.  I went ahead and reinstalled it with a new thermostat, new gaskets, and some of my own RTV sealant. Unfortunately I can't test the water temp today because I am also having carb issues. I'll get an answer here as soon as I can! John
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gun-driver
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Posted: September-12-2021 at 7:06pm |
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That's all the cleaner as it needs to be, next thing I would do is order the correct gaskets.
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8122pbrainard
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Posted: September-12-2021 at 7:24pm |
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The housing looks great. It will work.
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67 ski nat
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Posted: September-14-2021 at 8:40am |
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That muratic work fair. Good to know when they stop selling phosphoric Can not find good Ole MEK in California |
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67 ski nat
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Posted: September-14-2021 at 9:17am |
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I have tried ‘evapo-rust’ (environmental )
Works good. Needs wiring brushing every couple hours, then sparkles |
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Gary S
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Posted: September-14-2021 at 12:58pm |
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Soon you won't find bacon either.
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67 ski nat
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Posted: September-14-2021 at 3:11pm |
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Gary just went political on us. But he’s right
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8122pbrainard
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Posted: September-14-2021 at 5:01pm |
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Only in California!
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67 ski nat
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Posted: September-14-2021 at 5:23pm |
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I am looking for another state actually
Tennessee, Texas, are in running |
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john_sn
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Posted: September-23-2021 at 4:20pm |
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Hey all, I'm back. Unfortunately I have more questions than answers now. I got my carburetor working again and fired up the engine but its still sitting right around 180*F once warmed up, either at idle or under a load. Things I've checked
Since you all know a lot more about this from me, I took a short video of the engine operating, maybe you can spot something that's off. https://youtu.be/HK9jU9XF7ek Some things im unsure about:
Other than these, thought, the boat runs well. It picks right up from idle and accelerates smoothly to WOT. Temp needle stays close to 180 even at WOT. Thank you again for your help, John |
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gun-driver
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Posted: September-23-2021 at 5:00pm |
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I could be that your exhaust risers look like your thermostat housing and not allowing the proper amount of flow through the motor.
Can you run it on a traiter and see how the flow is out of the exhaust. If not another poster that had a hot temp problem took off the exhaust hose at the riser and ran with 5 gallon buckets under them to check flow. |
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KENO
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Posted: September-23-2021 at 5:56pm |
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What's the temperature if you aim the IR gun right where the temperature sender screws into the intake manifold? Is it 180 also or something different? .
You may think this is a silly question, but what do you have for supply voltage at the back of the temperature gauge? If your dash voltage is lower than normal, your temperature reading will higher on the gauge You can see this if you flip your blower on, drawing more current from the dash wiring and the temp gauge will go up some. Same if you turn the running lights on. Turn back off and the indicated temperature goes down again. As far as your hose size difference, you have a Commander engine with PCM manifolds and cooling system. The Commanders had 1 1/4 hose to the original pump. The pump you have now uses 1 inch hose. None of this will affect your temperature.
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KENO
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Posted: September-23-2021 at 8:19pm |
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Since you asked..............one thing that's "off" that has nothing to do with your cooling issue is that nice shiny Holley Street Warrior carburetor, that somebody put on because it's a lot cheaper than a marine carburetor. There aren't any streets on the water though and it doesn't meet USCG requirements for external fuel leakage allowed for a marine carburetor, so on an unexpected bad day, you could have a fire or explosion on your hands. Here's a street warrior in the link for comparison to yours in the video Your throttle return spring isn't hooked up either
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john_sn
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Posted: September-24-2021 at 4:28pm |
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gun-driver, I'll have to pull the boat out of the water to get a good look at the exhaust. I should be able to find time this weekend. Keno, When I aim the IR gun at the temp sender it reads 163. Turning on my blower and nav lights does bump up the needle a little bit, maybe 5-10 degrees. The voltage supply at the back of the temp gauge reads 11V I know that somebody who put the street warrior on my boat - its me. Well, its the same carb that the previous owner had on it. I took it apart to do a rebuild, and several of the fuel bowl screw holes got stripped, as well as the accelerator squirter screw holes. I had to just order another one. I didn't think much of it being a street carb, but you have me worried now. And good catch on the throttle spring. Thank you for taking a look. |
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KENO
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Posted: September-24-2021 at 8:11pm |
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I'm thinking that your IR gun shows some pretty normal temperatures and maybe you should trust that more than the gauge, especially if your voltage to the gauge is 11V.
Is that 11 volts while the engine is running? You could run the boat without the thermostat and get some readings that could be helpful. Especially down in some warm Mississippi water, having no thermostat isn't gonna turn it into an ice cube Speaking of voltage, I also noticed what looks like a 1 wire Delco alternator on your engine. If you want to verify that it's a marine alternator look at the back and see if it has screens like in the picture below. There are also screens on the front but they're harder to see because the fan partially blocks your view. Not all marine alternators have screens but your Delco should. It's a 3 wire Delco in the picture, but the screens are the same Just trying to keep you safe Hard to tell but I think you have the screens As far as the carburetor, there aren't huge differences but the main things dealing with leakage are J tubes on the bowl vents on later marine Holleys after about 1977 and special throttle shafts.They don't totally prevent external leakage but function to minimize any leakage to meet a USCG spec. Your rubber fuel line from the pump to the carburetor should be USCG approved stuff. You'll see lettering on the rubber stating that it's USCG A1-15 or A1-10 rated for example. If it's not USCG approved, it burns through quicker in a fire situation. And about your throttle spring, they don't call me Ole Beagle Eye for nuthin'
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john_sn
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Posted: October-04-2021 at 2:15pm |
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gun-driver, I pulled the boat out of the water to get a look at the exhaust flow. Here's two videos. The first is at idle RPM, the second is just above idle at 1100 RPM. Keno, My alternator looks like yours, with screens but with one wire instead of 3 so I think im okay there. My fuel hosing however has no lettering. I'll order new USCG approved hosing. Thank you for looking out! -John
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gun-driver
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Posted: October-04-2021 at 6:56pm |
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That water flow looks pretty good to me, even amount from both sides.
Guess it’s time to take a look at the wiring.
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john_sn wrote: