Over heat issues

[KB]

Hey guys wanted to reach out and get some opinions before taking the boat in as I like to do all work myself. 3 years ago I installed a reman power head on my 1998 200 efi Merc. When doing so I installed a new water impeller and housing. New water pressure gauge. Not long after my engine would sound heat alarm while slow trolling like going through a no wake zone. I'd shut it off and 3 mins later fire back and go on. Kept doing this for some time so I ordered and installed new thermostats. Problem solved or so I thought for about 3 months. Started to so it again every trip out of no wake zone. I'd turn it off and start back up after a couple mins. All the times it does it water pressure is about 5 to 7 psi. I looked up on line pressure and this is fine. I can ride on plane all day at 12 to 15 psi and never over heat only at slow speed. And never at idle. So I ordered another set of different brand thermostats and installed and first trip out did it again. I know it's not a fault in the temp sensor as hooked up to muffs after slow throttle for a few minutes the water coming out of pisser is very warm when alarm goes off. I've been riding like this for some time just knowing that going through no wake zones I'll be turning it off shortly and then re start and take off and I'm fine. Bit now I'm getting tired of it and want to fix it. I've heard people talking about popet valves and cutting a spring out of it but have no idea. If any one has an idea I'm all ears thanks guys

[mwardncsu]

Have you changed the impeller since the first one 3 years ago? The recommend very 3 and mud and such can do them in - and we know you like to go muddin’


My Yamaha will throw an overheat alarm after running hard then sitting idle / all while the temp gauges show normal. I think it’s recirculating warm water in. We changed thermostats a few year ago and it still does it I changed the poppet valve last Spring and it happened once last Summer. I turn off the motor and right back on and the alarm silences and all seems fine / who knows

[31Airborne]

I'm with Mike - 3 years for an impeller is a long time. Chances are the ends have turned a bit.

[KB]

Thanks guys this is on my list of things to do only prob is this started when impeller was only 3 months old or so. Problem started soon after getting boat power head. I do need to change impeller just not sure this is the issue.

[johnr]

Ive got an 09 etec on my duck boat. It sees lots of sand and mud. 6 years on the first impeller, 4 on this one. I remove it before each season to inspect it along with the lower unit because its hard to keep sand and silt out of it. Thats beside the point though.

I replaced the first impeller because of very low water pressure and volume at idle speeds. A new impeller only marginally increased pressure. Upon further inspection, the waterline leaked in the mid shaft area, because the metal waterline had been eroded by constant sand and mud, and the junction between plastic/rubber and metal no longer sealed. So at low rpm, enough water leaked to drastically reduce flow. At higher rpm, the impeller can make up the difference.

I replaced the tube and seal and it improved conditions.

[stripersniper73]

I would try a new housing and impeller I have seen a smudged housing cause low pressure also make sure you didn’t catch rubber grommet with water tube seen them rolled some and cut water flow down