1990 mercury black max 135 2 stroke overheating

[emoney]

A different brand maybe has different opening temps? I would think the 150 at cruising speed would be considered normal. I had a Johnson back in the day that would run 160 and we never found, nor had a problem.

 

[racingdave]

What do you guys think about this?one pic is cruising and one is idle zone.The motor runs hotter through idle zones and cools cruising its been that way for years and runs good.At one point i had it better, now it is back to this again i just deal with it.I suspect possible poppet not seating all the way iam not sure.

 

[Faztbullet]

Where is sender mounted???

 

[racingdave]

Looks like it has two of them both mounted on the top of each head.It is surface mounted

 

[Faztbullet]

It is surface mounted

There be yer problem..depending on where and how tight sender is mounted it can read high or low. Temp gauges with degrees cause more ghost hunting than their good for. Install the Merc OEM gauge like below or a pressure gauge...

 

[Dukedog]

Looks like it has two of them both mounted on the top of each head.It is surface mounted

one in tha starboard head is over temp (one wire, tan or tan/blue).. one in port head is temp gauge (two wires, black, tan or tan blue).. like faz says those gauges are known for being inaccurate.. only true way is compare with temp gun.....

 

[Texasmark]

Your experts are doing just fine and I thought I'd toss in a couple of generic comments:
The powerhead doesn't suck, it's driven. Openings at the output of the water pump surely will reduce the water pressure up through the block....aka your seal reversed comment.

Stats work up to around 2500 rpms. Above that water pressure "normally" pushes the poppet off it's seat (against spring pressure) and opens a much larger flow port. If you problem isn't below 2500 rpms (for a number) it isn't the stats per se. Clogged cooling passages, after what you said about sand, surely would have to be explored.

Most stats have opening temp (tolerance expected) stamped on the bottom of the pellet. The OT sensor closes at 195F (with tolerance) on 3 and 4 cylinder Mercs.,,serv. manual. data.