Optimax 115 overheating issue

[Nate1028]

Hi all, I’m having an issue with my new to me 2004 optimax 115. S/N 0T845869. The motor has about 130hrs on it and has a new impeller. At idle (in water) water pressure is between 1 and 2 psi and temp runs between 130 and 145 (bounces around a little assuming due to the thermostat opening). On plane pressure is around 12-14 psi and temp is 110 or so. I can run on plane or idle all day with no issue but… if I’m on plane running for a few minutes then back off of the throttle to I guess around 2000-2500rpm, pressure drops to around 8 psi but temp immediately spikes to 180 and I alarm. I wait for it to cool a little and it fires up and temps stabilize again. It’s EVERY time I come off of plane. Ordering a thermostat and gasket today but I’m not convinced that’s the problem. ANY input would be appreciated.

[JOE54]

mounted on jack plate ?????

[Nate1028]

No. Mounted directly to a tracker v17.

[JOE54]

id look at poppett also, did it do it before w/p replaced ????

[Nate1028]

I got the boat over the winter and did the impeller before putting it in the water. It was the original impeller so I wanted to replace it before I ran it. I ordered a thermostat and poppet set and will hopefully be replacing that this week. Not sure if there’s anything else I should check/replace while I’m working on it.

[JOE54]

good start

[Nate1028]

Just a quick update… changed the thermostat and poppet and also dropped the lower unit to check the impeller. Cleaned the gasket mating surfaces on the water pump (there was still some corrosion I didn’t notice the first time around). Tested it today and water pressure at idle is over 3psi. No over heating issues at all. Thanks for everyone’s help.

[JOE54]