johnson 175 GT cooling port side only

tom d boater

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Hi, I have a johnson175 gt, late 80's i think, it only seems to be cooling the port side, i have had the lower unit off to replace the impeller and had the thermostats out and ran a hose through the cooling system and nothing goes through the starboard side. help
 

boobie

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Re: johnson 175 GT cooling port side only

You may want to pull the heads off and check the water defelectors in the block to see if they are swelled up blocking water flow.
 

tom d boater

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Re: johnson 175 GT cooling port side only

thanks, am going to take the engine off the boat and get it in the garage, it's turning into a bit of a restoration job.
 
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Re: johnson 175 GT cooling port side only

How do you know it's only cooling one side? Have you taken temperature readings, and if so what are they?
 

emdsapmgr

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Re: johnson 175 GT cooling port side only

Before you take too much apart, you might remove the starboard head cover. You don't have to pull the head. You will be able to see if there is any debris inside the head cooling passages which may be blocking the water circulation on the one side. If those passages look clear, then pull the head and inspect the water diverters. The stats open at 143, so the engine should idle between 143 and 155 degrees, depending on how cold/warm the water is.
 

tom d boater

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Re: johnson 175 GT cooling port side only

hi, i have taken the thermostats out, and while i have got the lower unit off i attached a hose to the cooling pipe inside the exhaust housing and ran the water until it came out of the pee hole, then checked in the thermostat holes, there was signs of water in the port side and not the starboard, then i replaced the port side thermostat only and re tested with the hose, the theory being that no water should go through the port side because of having a thermostat in, when i checked in the starboard side there was no sign of any water, it was bone dry. i have ordered a new impeller and seal kit and gasket set for the power head so i will go through the whole system. i think that the previous owner/s didn't flush the engine at all, there is a large build up of salt and crud around the thermostat, so i'm going to play it safe and go through the whole thing properly. have just built a trolley and going to remove the engine from the boat and get it in the garage. cheers tom.
 

tom d boater

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Re: johnson 175 GT cooling port side only

i did remove the head cover and although it wasn't spotless it looked clear, no blockages, just starting to think that i've bought a neglected engine.
 
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Re: johnson 175 GT cooling port side only

Just a thought, don't know if it applies to your engine or not because I don't see the year. If your engine is supposed to have a water control valve and a previous owner has removed it you'll have cooling problems. Look at shop2.evinrude.com to find your engine diagram and see if it has a water control valve, then check your engine to see if it's there. My 200 GT had that situation, one side or the other would cool. May not even apply to you, but it's worth checking.
 

emdsapmgr

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Re: johnson 175 GT cooling port side only

If you find some debris restricting the water passages under the head cover, I'd pull the head. It is very possible that you have crud buildup in the water passages, esp by the rubber water diverters. It is very possible that the water flow past these diverters may be plugged, or at least severely restricted. If you find some severe restrictions in the powerhead, I'd also remove the flywheel and the water cooled rectifier/regulator. Have a look inside the block between the two heads for additional crud buildup.
 
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