Mercury 150hp Optimax Cooling System

[CJL]

Just fishin' for some re-assurance.
I was out on my boat on Sat on the Thames. Launched and engine ran fine for 1.5hrs. Had lunch (engine was down) then set about to return home. After 20mins Smart Craft dials set off the alarm and a "overheat" was displayed on the tacho gauge. I checked the tell tail and it was not running. The exhaust or block did not feel excessively hot.

Got back to lauch site (let it cool down, run it, let it cool down, run it etc) without the engine gaurdian system cutting in and noticed something up the tell tail. I`ve now cleared this (general Thames cr*p) and I`m gonna arrange a day on a fresh reservoir to give it a proper flush.

AND THE QUESTION IS:
Is it likely that the non-running tell tail is enough to set off the alarm on the smart guages or does the problem lie deeper?

(Deeper = £150 for a mechanic to look at it)

Your thought are greatly appreciated!

Chris

[Pete7]

Something simple like a plastic bag over the water intakes would stop the supply of cooling water to the engine, cause the alarm to activate and stop the tel tale. When you stopped the bag falls off and the supply is restored.

Tricky to know what to recommend. If it now works fine how about just inspecting the water pump. Seven bolts (ish) in the lower leg (one under the trim anode) allow the gearbox to be dropped and then undo the water pump housing bolts. Check condition of rubber water pump and vanes. Smear the pump with grease and bolt it back up. If you change the rubber pump make sure it goes back on the right way round.

Remove the tel tale pipe and rubber tube and blow through to clean, they do block at the slightest excuse.

Hopefully the guardian saved the rest of the engine, afterall thats what its designed to do.

Pete

[Daniel]

Originally posted by CJL
Is it likely that the non-running tell tail is enough to set off the alarm on the smart guages or does the problem lie deeper?

IMHO unlikely although it could have course been combined with a plastic bag or something at the same time??? I'd do as Pete suggests, and if you can't/won't let someone else do it, even with a £150 bill not just because it might save your engine, it also might save your life?

[Paul F]

your smartcraft guages gives block pressure, what is it at on idle??should be i think amin of 3psi(will check on monday)this will tell you whether you need to drop gearbox. what was block temp when guardian cut in??

[CJL]

hi people, just run my boat in a local reservoir. Ran fine and temp dropped as speed increased - to be expected. At tick-over temp was around fourty to fifty degrees. Block pressure was happy around three psi and the tell tale was strong. I'm going to run up the Thames to Chertsy tomorrow so it should getting another good flush. I'm happy it was just the blocked tell tale that set it all off. Thanks for your input everybody.
Cheers,
Chris.

ps I'd still be interested to know that psi off your o/b, for comparison.