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Discussion Starter #1
I have a 1997 Evinrude 90 SPL which I'm planning to sell in a month or two. I have had the motor serviced by a proffessional every year.
This spring after attaching the hose ot the lower unit to start it, the motor overheated after I ran it for a few minutes. I have had this problem before and blamed it on sticking thermostats. The service guy said that the motor wasn't getting enough water with the hose and thats why it took a little while to overheat. He said I nedd to put it in some" real water" to give it a good test. He thinks its all right.
By the way, the water pump was replaced before last season, about 30-40 hrs ago. Also when I start it, after about 20 or 30 seconds, waterstarts to flow out the slots just above the cavitation plate. I've always thought that this was a sign that the t'stats were opening.
I sugested taking out the t'stats but he says this is not a very good idea.
Taking the boat to a place where I can test the motor is not practucal and besides I'm leaving for the shore next week.
Do I have a problem?
Anglerdave
 

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The water flow which takes about 20 to 30 sec sounds like a long time. Water will flow all the time all the t stats do is open up to allow water to circulate around the block. You can take them out and put them in a pot of water with a thermometer. As the water heats up watch and see when they open up and if they open up. If you are not getting a good steady stream out of the piss hole than you coul have a clog or the water pump is not working properly. If you have sucked up any mud that could clog the engine and/or ruin the water pump. One other thing did they replace the entire water pump or just the impeller? If the whole thing was not replaced that could be the problem. The mech said that the hose was not enough water. Have you ran the engin in the past without this problem? If so it is not likley to be the problem. Sorry if I rambled on
 

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I'm with Bryanfish on this. He's got everything right.

BTW, if you're motor overheats on the hose, something is wrong. A proper running motor will NOT overheat on a hose.

- Dae
 

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Discussion Starter #4
Thanx for the replies. How big a job is it to replace the t'stats. Is this a job for a do-it-yorselfer? It is certainly possible that I could have sucked sand or mud into the motor. The motor ran fine lst fall.
I forgot to mention that I have a water pressure gage which is connected to the water line just before the tell tale. I wsn't getting a whole lot of pressure on it but I never have when the motor idles.
 

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Not sure if your 90 is like my 96 115 Rude, but if it is, the tstats are on the back side near the top. All I need is a spark plug socket to change mine. Basicly, its as easy as it is to take a lug nut off a wheel.

- Dae
 

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The T stats on my 150 johnson are on the back side of the motor about all the way on the top half. They are about 1 1/2 inches round with a nut on the top of them all as one peice. Its a very easy job to remove them but I would check them first as I mentioned above. You have to look at them pretty close because they do not open very much. Check your lower intake where you put your rabit ears and see if they are clear. You can try to keep running water through the motor and maybe it will clean out any sand or mud while the engine is off. The water guage you have on the boat if you increase engin speed does the preasure increase and does your water stream increase? If not I think your back to the water pump because even if there is a clog what is coming through should increase. Also that long time for water to start coming out leads me back to the water pump and it maybe scared just enough to effect its performance.
 

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One other thing you could try if you have a garbage can that you can get around the motor that will have the motor deep enough for the intakes that will work. It should do the same as putting the boat in the water.
 

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Discussion Starter #8
Yhanx all for your input.
No I don't have a garbage can big enough for the lower unit. But I may try to buy one.
The 20-30 sec interval after the motor starts and before water comes out the slots above the cavitation plate was just an estimate. It may not take that long.
The water pressure gage does increase when I rev the motor but I can;t remember the pressure when with just the hose.
Anyhow I'm taking the boat to the shore probably wed so I try it down there.
Thanx again.
Dave
 

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take out the thermostats and beat them against your hand, you will be amazed at how much sand and grit will come out of them. They arent that expensive to replace if you are unsure of them. i would say drop the boat in and run it to see if it is overheating. dont spend a bunch of money replacing things if they are fine.

oh yeah and sometimes the rubber seal under the thermostat cap will be eaten up and need replacing when you take it off. it is definitely worth the 20cents to get new ones. They make sure that cap is snug and keep water from seeping down onto your spark plugs and wires.
 

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The Pee hole under the lower cowl is where you need to see water streaming from! ( Don't launch it until your sure its pumping water! )only takes a few mins to burn the power head up. if its heating on the garden hose its most likeley the water pump/housing.
 
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