Sending unit placaement

[Carter Powell]

On a 2.4 EFI BP can the sending unit hole in the starboard head which is used for the warning horn sending unit be used for a temperature sending unit instead? Also, what is considered safe or proper water temperature in the head area. On the port head where the sending unit for the cylinder head temp is located, is this an item that is really needed?

Many Thanks

Carter Powell

[us1]

I only run water temp not cylinder head temp I install it in the top of the head and run it up to 110 Degrees. Cylinder head temp can be taken from either head.

[Talon2.5]

i use a cylinder head temp sensor and when it got up over 180 on the guage this is what happened now with a rebuild and thorough inspection of ALL things connected with the water pump it runs a cylinder temp around 160 cruising and 150'ish full out


skip

[us1]

Hey Skip, how many RPM are you turning those production cast pistons at.

[Talon2.5]

if the tachs right which it seems to be, 7200 and then boom right after it got around 181-182 degrees, 7200 aint bad for a stock piston in any way, they should live fine at that rpm as long as everything else is operating properly


skip

[us1]

7200 will work. This is interesting, the Mercury 2.5 car has a radiator for water-cooling and it run at 220 degrees cylinder head temp all the time, this is with good water pressure though. If the water pressure is not high enough you will develop steam pocket around the cylinders and end up with pistons like the ones in your picture. I love these post about how people are running 8-lbs. water pressure with no problems. I would love to pull a head and drop in a bore gauge and check the out of round and taper.:)

[NPW]

Carter, On My bridgeport EFI Horn motor I leave the warning horn in the starboard head tapped the water temp gage into the port..Until I changed out the ECU she ran about 190 on long hi RPM runs with 30 lbs gage pressure through a bobs cone and 1/8 " washers...now after changing to diff fuel curve she runs about 120/130.. John as far as RPM's have turned her to 8800 for the win, usually try to keep max to 7500 using amsoil at 32/1.She does a leak-down at 5% on worst cylinder so I guess she's not to egged in the bore..these are really tough old motors just keep the mixture right and don't go over 25 on max timing.. :D love those mercs

[us1]

Your Bridgeport has forged race pistons in it and should turn 8000 plus with no problem. With 30-lbs. water pressure you will not develop steam pockets but a Mercury engineer once told me that over 25-lbs. water pressure will blow through gaskets.

[Talon2.5]

funny thing john, i had around 25lbs just before that also, i never positively nailed down what caused that exept the 180 degree temp was the highest temp i ever had with any of my mercs and make sure i havent had it again :confused:



she's ok now though:D

skip

[us1]

Is hard to tell some times what really blows them. I don't recommend running 220:eek: on an outboard but I thought it was interesting anyway. When you tear his motors down the bores are as straight as can be??????:confused:

[Tom D.]

Carter,
I Think the sending unit in the port head is the one you want to use for a gauge. The one in the starboard head is for the horn and has different type of sender in which is either on or off. The port head sender verys in reistance to make the needle move on your gauge.

Skip,
That looks like it hurt your WALLET pretty bad!:eek:

[Markus]

John, do you know of anyone who has really experience water blowing through gaskets due to too high water pressure?

I am way above 25 on my Yamaha with a transom mounted pick-up if I have the thermostats in. I wonder if I should worry...

[Talon2.5]

check mate,

the old wallet was shaking in my pocket when it heard that motor knocking hehehe

it wasnt too bad, about 900 or so to redo it but it saves a lot of money when ya build your own powerheads, the crank was good thank god but some new pistons bearings gaskets rings a new block and front half bla bla bla, i came out of it farly unscaved, i damn sure keep an eye on it better now and havent run it much hehehe, the old wallet may have a heart attack the next time!!

but it was fun building another one


later
skip

[us1]

I have never seen it happen and it sounds impossible but the Mercury engineering department said this would happen so I thought I would relay it. The only place I would wonder about is the little strip of gasket on the exhaust divider feed passages.

[Hunter]

My bone-stock 2000 225 Pro Max shows 150 - 180 degrees depending on the air/water temp. Generally, it's around 170 at 6000 rpm with about 12 psi on the gauge.

My point is that it's holding up and, according to Merc, at in an appropriate range. To assume that Mercury makes no effort to develop their cooling systems or are hiding tremendous performance increases parallels the 100mpg carburetor urban legend. Once altered, your engine's a test bed and although many may pursue similar methods you've lost the baseline research Merc's put plenty of hours into developing reliable power.

Most folks' boats here can crush mine on top end. If going faster than I do was an imperative I'd probably modify my engine. But to add to every post that you do your own work and then continually post stories of how your engine grenaded at a temperature Merc and many others find acceptable is at best disingenuous to yourself and others.

[NPW]

where did that come from, Skip?

[us1]

Hi Hunter , how are you. When are you comming back to this side of the world.:)