does a I/O have a thermostat

roffey

roffey

Junior Member
I had the boat out today for my first test drive. All went well other than the wind was bad. Made it almost impossible to trailer the boat. The boat seems to run hot. My question is does a I/O have a thermostat or does the lake water just run through it constantly?
 
its got a thermostat, but odds are, you need a new water pump impeller(its on the out drive, not on the engine). Its the first place to start looking
 
Yes, but alot of people take them out. Also if you have an ALPHA or earlier outdrive, it also has poppets most likely to maintain water pressure to the engine block.
 
The reason I thought thermostat was the temp went up real high.. then went to the middle of the gauge, almost like the thermostat opened. This is a bigger boat, 26 ft. When testing I had it WOT for the most part. I may have been pushing it a little. It was my impression if you have the gas you can run wide open all day.

I will check the water pump.... and by the way.. even with 4ft chop heavy winds and bow spray soaking us.. if was f**king fantastic.. I love it.
 
water pump impellers on mercs are an annual service item, don't forget to top off the gear lube when you're done. If the impeller checks out, and you replace the thermostat and it still overheats, sounds like you may need to check the manifolds and risers for blockages
 
the check balls Ferm is talking about are inside the hoses that go to the risers, its in that T fitting in the top of the housing, if they aren't in there, or if the spring is gone, it will overheat
 
spareparts said:
the check balls Ferm is talking about are inside the hoses that go to the risers, its in that T fitting in the top of the housing, if they aren't in there, or if the spring is gone, it will overheat
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Wow really?? I did not know this. I thought they stopped water from flowing, not used to make it flow.....
 
The check balls restrict the water flow so the block will stay full once the block is full of water the check balls allow the water to flow past ton the risers. It prevents steam pockets and promotes even cooling
 
I am going to check all that you people have suggested. for sure. The last time I was out on the boat the temp did go down to normal so I thought something might have been stuck.
So I took the boat out for a big cruse on Saturday, what I noticed was if I pin the boat it will run hot, very hot like 200-220. If I cruse it runs 160-180. Do you think it could be the water is running through the motor to fast and does not have time to cool it? Maybe no t-stat or a stuck open t-stat?
Just running ideas by you people as [FONT=Calibri,Times New Roman][FONT=Calibri,Times New Roman]sit here at my desk, looking at my computer, working, looking at the sun thinking I could be on the water or working on my boat….[/FONT][/FONT] v1
As I said I am going to check all you said...​
 
start with the water pump, look closely at the water pump housing, if you see any of the plastic melted, replace the housing as well. First tip on replacing the water pump, put the drive in forward before dropping the lower unit, second tip, there's a bolt under the trim tab
 
I did a quick search on the internet, most places take it to a shop. Is it complicated to replace the water impeller? Can I do this in my driveway? I don't have a problem giving it a try.​
 
OK so I finally got some time. I took the lower unit or out drive off the boat and replaced the water pump or impeller. What I did was to start the boat with the thermostat housing removed. I could see no real water movement so I was confident the impeller was the problem. Just as you people said it not that bad. Here is a pic of the old impeller, not sue if I needed to replace or not.

I think it was a couple of years past due, LOL
 

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........... and to answer my own question, no there was no thermostat. My next question is should I put a tstat in? I still have it apart as I have to replace the gasket and can't get the parts until Monday or Tuesday as Monday is... CANADA day... :happy:
 
Conceder it done, you were the guiding force for the water pump. It was so bad it makes me wonder how the previous owner winterized it?
 
That impeller got run dry is what did it in. You can tell by the wear on it as age tends to just lay the vanes over whereas running it dry burns them off. And put a 140 t-stat back in it since it is a raw water cooled engine. You could do a 160, but the 140 seems to work better and reduce temp spikes from my experience.
 
THEFERMANATOR said:
That impeller got run dry is what did it in. You can tell by the wear on it as age tends to just lay the vanes over whereas running it dry burns them off. And put a 140 t-stat back in it since it is a raw water cooled engine. You could do a 160, but the 140 seems to work better and reduce temp spikes from my experience.
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what he said!

take a long look at how the thermostat is installed in your housing, its easy to put it in wrong, just find the right parts break down and it should show all the parts in their correct order
 
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