I wanted to get a couple of opinions on this issue. I have a 2002 Mercury 200. I’ve had the alarm go off a couple of times when accelerating. The alarm has not gone off when accelerating slowly and steadily. This last outing, it was going off even at idle speed. There is a new impeller and a steady flow coming from the tell tale. I ran the motor on the hose a few times and the alarm never goes off. The temperature of the water coming from the tell tale is 138 degrees. I’m not sure what the problem could be. I’d appreciate any ideas.

I would check thermostats and poppet valves....

need a water pressure gauge ta give ya a direction..... stats ez ta check, poppet not so much.

new impeller is ok but did you change out tha complete pump and assy?

something we use ta do with almost anything over heat V6 merc was new pump kit, t-stats and poppet assy. anytime we had a heat problem... pretty cheap ta do and eliminated tha problems 90% of tha time.... especially if it was an older and/or a motor we had no history of....... saved lotta time and head aches.....

but a gauge would go a long way with findin' tha culprit...............

I would backflush the motor and the pull/clean the "strainer assy" first before diving into t-stats and poppet valves.

Yep, strainer first, then thermostats (just order new ones & gaskets).

https://www.bbcboards.net/showthread.php?t=565408

doesn't have a "strainer assy"..............

No? Is that motor still an EFI?

didn't say.... doesn't make any difference, still no "strainer"..........

What year did they start installing them?

didn't know they did?.. maybe on tha 4 strokes?.. ya gotta part number for any kinda "strainer assy." that has ta do with coolin'?.. any merc V6 motor???

tha last merc i had was an '07 280.... no strainer....

tha efi's did have a water separator filter............. nothing ta do with coolin'........

ya really need a water pressure gauge, especially ona older motor.. it can tell ya a lot 'bout what ta look for............

Oh, I thought you were a mechanic. There absolutely is a strainer on all of the optimax, some of the older ones have the strainer up higher on the block. Mine (2005) is lower port, down about the bottom cowling height. They are notorious for getting filled with grass/scum. Kind of a bad design and a pain to get too.

From that I’ve read the XB didn’t have one, so maybe your racing motor didn’t either.

We recently had a very similar experience. Thought it was an over rev or over heat issue. It ended up being the stator/rectifier causing an over charge to the electrical system. It started from a loose starting battery connection. This made the rectifier go bad. Our mechanic diagnosed and fixed it in about 30 minutes. Thankfully, it was an easy, inexpensive repair. Good luck!

shoulda mentioned that i'm not an green (opti-pop) motor kinda guy.. jus never interested me since ya can't "turn up tha wick" on 'em.....

looks like its an optimax only... did someone mention CHECK THA STRAINER!!!....
if its an OPTI?

[quote=grout-scout]

Oh, I thought you were a mechanic.

From that I’ve read the XB didn’t have one, so maybe your racing motor didn’t either.[quote=grout-scout]

just on tha normal v6 merc.. no opti's and/or 3.0's so don't know 'bout tha XB either.............. not a year/model from 2.0, 2.4. 2.5 production or hi perf. from 1976 (my first one that was one of tha first ones in tha dfw area) ta 2007 owned/operated at some time or another....... very little i may not know about any of those................ T