temp Gauge

[DavidP]

The Temp gague on one of my engines runs up to running tempreture then a few seconds later drops back to zero ,then back up again then down to zero ,all the time the engine is running ,any ideas why ,
It only started happening after i moved away from shallow water, the engine was only a few inches off the bottom ,it doesnt seem to have affected anything as this happened yesterday and i have been out today.

Cheers Dave.

 

[ccscott49]

That sounds like a faulty gauge, as the gauge is in the fresh water side of the cooling system, its just not possible for it to drop to zero in a matter of seconds. But and it's a big but! You could also have an airlock in the freshwater side of the cooling. Have you ahd anything apart? and is the level ok? If no and yes, it's probably the gauge.

 

[DavidP]

Cheers Colin , I didnt know i had a fresh water side on the engines ,where abouts are they,
i have 4.3 V6 mercruisers

Cheers David.

 

[ccscott49]

They are inboards?

 

[MapisM]

The fresh water side which Colin mention applies to the so called "closed cooling", which as far as I remember is optional in your engines. I would be surprised to find it if you did not ask for that, but do not take my word for it.
Anyhow, one advantage of twin engines is the possibility to cross-check the instruments.
Just invert the wires on the temperature gauges. If the problem stay on the same gauge, that is definitely the faulty component.

 

[DavidP]

yes inboards petrol,with alpha 1 legs.

 

[ccscott49]

OK, they will have a fresh water circuit, with a filler cap (radiator type) somewhere on top of the engine. You need to check this water level and top it up with appropriate antifreeze mixture. You will need to check that in the owners manual. If all is ok, you have a dodgy gauge, or dodgy connection to the gauge/sender, if you are not mechanically minded, it might be worth your while asking a friend who knows these engines or the dealer, it's not a good idea messing with eletrical connections in the engine compartment of a petrol engined boat, in fact it can be downright dangerous! I don't think we are talking about lots of dosh here, so it would be sensible to get it done for you.

 

[MapisM]

Good thing the Internet.
It gives an alternative to silly TV programs when at late night one can not sleep...

Colin, why are you so sure that David's engines have the fresh water circuit?
Just had a look at Mercury site (having time for that - see first sentence !): there are 3 versions of the 4.3 V6: 190, 205 and 210 hp, but the closed cooling is optional in all of them.
Possibly Sea Ray is putting it as standard in all its boats?
Or is it mandatory in the UK market, for some reason?

Anyhow, you're absolutely right in recommending not to fool around with wires in the engine compartment of a petrol boat.
What I meant in my previous post was switching the port and starboard wires directly on the gauges.
Depending on how good is the access to the rear of the dashboard, it could be easier done than explained.

 

[andyball]

quite right too...

all the s/h boats with mercruisers I looked at were raw water cooled....and yes in the UK.

& frankly, if someone doesn't know what they're doing,best not to "fool around with with wires" at all...petrol or not: a fire's a fire.

but swapping sensor/guage wires (if they'll reach) is very sensible, or swap the sensors over.