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my 1990 SN is experiencing some temperature issues. The local marine shop has changed my timing and put ac delco plugs in it and since then the temperature has been acting up. I was getting temps up to 175. I changed the impeller and the thermostat (143 degree) and the temp is now around 150-165. It will stay at about 160 during normal cruising speeds and get upt to about 165 at full throttle and will gradually come down to 155-160 after a little idling. The boat always used to run at 140 no matter what. I cant figure out why the temp is fluctuating now all of a sudden. All lines are clear no debris and all hoses etc are tight. If i remove the thermostat the temp drops to 110-120. Do i have a new faulty thermostat??? Please help!
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RE: nautique engine temp issues
place the t stat in a pot of water with a therometer on the stove and heat it until it opens. Read the therometer to see if the tstat is bad. Sometimes they are. -
RE: nautique engine temp issues
I would ask the shop what they set the timing at. Should be 6-8 degrees btdc. I would also replace the plugs with autolite 24's(check your manual or maybe someone on this sight with a 90 can verify this). That should be what came in it.If the heat range on the plugs is wrong it can affect the engine temp. in minor increments. Do the t-stat check as stated by mrese.Comment
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RE: nautique engine temp issues
timing is set at 10 degrees btdc per the manual. The temp will go anywhere from 157-165. During normal cruising it is at 160. Full throttle it goes up to 165. These temps just seem high for a 143 thermostat. One other odd thing is it seems the drivers side riser is cooler than the other side. Is that normal or is there a potential blockage in there somewhere. Anyone shed any light on this or should I just leave it be and just run it as is.Comment
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RE: nautique engine temp issues
Check your sparkplugs to make sure they are t he right heat range because I have found some overheating problems linked to the wrong spark plugs espically at higher speeds, by the way AC plugs work better in GM engines and motorcraft orautolite work better in Fords. The manifolds may have a problem but you have to remember the water will flow out the side with least resistance, but check the under side of the riser that is running warmer than the other one to see if it colder at the bottom than at the top if it is then you need a riser gasket.Comment
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RE: nautique engine temp issues
The delco plugs dont have any markings on them just platinum they say. I wonder if this would be causing the extra increase in temperature and the fluctuation. It is really the only thing that has changed and now all of a sudden it runs hotter. How much temp increase is possible by using the wrong heat range plugs?Comment
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RE: nautique engine temp issues
Can you say hole in piston?Comment
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RE: nautique engine temp issues
yea i realize the heat in the cylinder, but how much could an incorrect heat range plug affect water (operating temp)????Comment
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