Cooling Relief Valve(s)? 1995 175 hp / 60 deg. V6

Okay, I'm stumped.

The issue is that my motor has normal temperature (160 deg) at idle and low speed, but runs hot (180-190) at high rpms.

The water pump is rebuilt and pumping fine.

The gauge seems to be fine, also. The motor comes off fast idle right at a reading of 140 (t-stats open at 143), and the needle is right where it oughta be at warm idle (160).

I searched the forum and read that this condition indicates that the cooling pressure relief valve(s) in the head(s) may be stuck closed. Sounds reasonable to me.

My dilemma is that Seloc says I have 'em but doesn't show them, the OMC shop manual doesn't mention them at all, and my OMC parts catalog doesn't show anything in the powerhead that looks to me like a cooling relief valve, nor do any of the exploded parts carry that description. Went to the Evinrude site, but that's just a repeat of what's in the parts catalog. No help there, either.

Anyone out there familar with this particular motor, or the 150 hp, which is essentially the same? Do I have these valves or don't I? I simply can't figure out exactly what I'm looking for, where it/they are located, or how to remove/replace it/them.

Thanks!

Re: Cooling Relief Valve(s)? 1995 175 hp / 60 deg. V6

Try the parts diagrams on the BRP website.

Re: Cooling Relief Valve(s)? 1995 175 hp / 60 deg. V6

It looks to me like the t-stats themselves could be the pressure relief valves. High water pressure could overcome the springs and force the t-stats off their seats in the head. That would allow water to bypass the t-stats. I have a 94 175 with a water pressure gauge but no temperature gauge so I have no idea about normal temperatures. Your temperatures seem high across the board though according to my OMC manual. By the specs. in the manual, the switch for fast idle should operate at 105 deg. The temperature should be about 140 at idle and must not exceed 160 at 5000 RPM.

Re: Cooling Relief Valve(s)? 1995 175 hp / 60 deg. V6

I just replaced the tstats on a 2002 150hp johnson today. It's the same as yours as in the tstats are held in the seat with a spring and the high water psi at highere rpm's pushes them off of there seat.

Re: Cooling Relief Valve(s)? 1995 175 hp / 60 deg. V6

That's interesting! T-stat springs as the pressure relief simply never occurred to me. Was looking for something more complicated (meaning, expensive)

Okay, if it's the t-stat springs that act as pressure relief, then that obviously isn't the issue. I'll need to follow this farther. I guess I need to find some thermomelt sticks and do a full test to make sure that what I'm seeing at the gauge is accurate. I can't think of any good reason for it to run hot. The waterpump is fine and all visible water passages seem clear, too. I have a really strong tell-tale at all speeds.

If anyone has other thoughts on this I'd be glad to hear them.

Thanks, folks!