Over heat alarm

[leadhead]

Hi
I have a couple of nagging issues with my 2005 90 HP Johnson saltwater --- the motor has 1500 hours on it and I fish in saltwater every weekend rain or shine --- but the motor is rarely run over 3500 RPM and never over 4000 RPM --- I do a lot of power drifting --- in and out of gear
1) in July on one of my normal weekly fishing trips the motor overheat alarm sounded and the low RPM limit was initiated --- I pulled the thermostats and continued on my way --- I purchased two new thermostats and installed them before the next trip --- but same scenario occurred as soon as I got up on plane the overheat alarm went off and low RPM initiated --- I got on line and the recommendation was that the water pump was worn --- I didn't think this was the case since it was only one and a half seasons old and I usually get 5 years from my water pumps before I change them as I’m never in shallow water and never pick up any sand --- I replaced the water pump and re-installed the thermostats but had the same problem at the beginning of the next trip with both the alarm and RPM limit kicking in as soon as I got on plane --- I fished the remainder of the summer season without the thermostats since there didn't seem to be any other reason for this problem to occur --- I figured that I had changed the only two heat related things that could cause this problem --- the boat is trailered and the motor is flushed with fresh water for 5 min after every trip without fail --- I am wondering if there is an issue with the thermostat seats --- since I understand that the thermostats actually lift out of the seats when the motor is at higher RPM --- or if there is anything else besides a faulty alarm system that could be causing this problem --- I'm still running every weekend without thermostats in 47 degree water --- can this cause a problem ? ? ?

2) A small round disfigured piece of metal 3/8” in dia. fell out of the same motor at the end of a trip a month ago as I raised the motor out of the water to load the boat on the trailer --- I could hear it fall inside the engine cover but didn’t check it out until the next day --- it is ferrous metal (sticks to a magnet) and looks like a disfigured ball bearing as though it had been pinched --- it was laying on the inside of the lower engine cover --- haven’t noticed any major issues with the motor but I can’t imagine where this piece of metal came from --- the starter had been replaced a couple of months before this happened but I did the work along with a friend that knows motors pretty well --- he has no idea what it could be --- are there any large ball bearings associated with the flywheel that could be the source of this item --- I figured if it did come from a bearing I would have had some indication by now ---
Sorry for the long message --- any help would be greatly appreciated on either issue
Thanks
Regards
Leadhead

[boats.net]

If this a 2 stroke engine then check for hot spots on heads, may have blocked water passage.
Only ball bearing is on crankshaft, if top main will out would probably have loose play in flywheel.

[leadhead]

Thanks for Quick response ! ! !

Yes the motor is a carbureted 2 stroke model # J90PLSO --- motor runs fine at less then 100 degrees without the thermostats in --- I only have the problem when I put the new thermostats in --- if I put in an older thermostat that opens at around 100 to 110 degrees F - only the side with the new thermostat gets hot --- the side with the old thermostat runs cooler and it doesn't matter if I switch sides --- the new thermostats open at about 160 to 170 F

Motor does not get hot with the new thermostats in at idle only at higher RPM under a load

How do you check for blockage ? ? ?

do the thermostat seats wear out ???

could there be a different diameter on the new thermostats that makes it stick in the seat and not lift out with higher RPMS ? ? ?

[boats.net]

That thermostat is used ao a lot of models so probably not wrong one.
Would have to remove heads and clean water passages and replace gaskets.

[leadhead]

Removing heads seems like a pretty drastic action for a motor that runs well without thermostats --- actual run temp without thermostats is unknown since water temp gauge starts at 100 F and reading is below that --- are there any other procedures that might identify a cooling problem or identify a problem with the alarm circuitry ? ? ?