Clamshell water pressure?

[9D280]

Any of you Merc gurus out there happen to know what the pressure of the cooling water at the top of the head is? Ideally both at Idle and WOT.

The engine has no alarm circutry whatsoever, so I am toying with fitting a water pressure gauge by either replacing the telltale outlet spigot with a T fitting or putting a separate spigot into the case at a suitable blanking plug point, then running a pitot speedo type hose to the console. Problem is I have no idea what range I'd need on the gauge.

[Nos4r2]

Originally Posted by 9D280

Any of you Merc gurus out there happen to know what the pressure of the cooling water at the top of the head is? Ideally both at Idle and WOT.

The engine has no alarm circutry whatsoever, so I am toying with fitting a water pressure gauge by either replacing the telltale outlet spigot with a T fitting or putting a separate spigot into the case at a suitable blanking plug point, then running a pitot speedo type hose to the console. Problem is I have no idea what range I'd need on the gauge.

Just run an extended telltale pipe up above the top of the water jacket before dropping it back down to the normal outlet place. If any area at all isn't getting water then it's going to stop peeing.

[9D280]

Agreed, but that still means I have to crane my neck round instead of just glancing at the console! (who just said "lazy"?)

Having said that, to get the exit spigot any higher they'd have had to drill the top of the jacket to fit it!

[free]

Would it not be easier to use a pressure switch and a buzzer/lamp? You'll still need to get the approximate pressure to size the switch.

free

[9D280]

Possibly, but taking that to it's logical conclusion At some point in the future I'll be fitting a depth sounder & plotter. Chances are by the time I get round to it all plotters will talk NMEA2k, so an NMEA2k sounder unit might be the easiest way to go, and if there's a network connection at the transom....

The biggest problem with a switch will be what do I set it at? At tickover there is a half hearted dribble. At half throttle the jet clears the toobs by about 3 feet! A switch will likely mean I am guaranteed a beep as soon as I throttle back, or if it's set to not squeal at idle, the warning will be too late at WOT.

[dougcrock]

hi R
why fix what aint broke

[9D280]

Would you disconnect all the warning gubbinry on your engine & go cruising?

It's not so much a case of "not broke" as "not there"!

Right now I have an engine that even as sold had absolutely no monitoring / warning equipment bar the telltale. I'm trying to improve on that situation.

[dougcrock]

maybe not the fridge
what about audible overheat alarm
easy to bond thermo on to some bit of casing

[9D280]

Yeah, that's nice & easy - one of them was an optional extra when it was originally built! My concern with overheat is a good chunk of the damage will have been done by the time it actually goes off, if its set at a level that won't give false alarms on "slightly too warm". I'll be fitting one of them as well - the buzzer & wiring is all still there as a hangover from the Yam.

[dougcrock]

we had merc 65 red band 4cyl for yrs & yrs boat fell apart before engine never any probs as long as fuel mix ok ish
see you next time your out
any plans
D