Waterpump Question

[stopngo]

Hello all

Started up my 1976 Merc 850 Today first time in 2 years and started up immediately and Decisively of which I am pleased.

My Question: I do not see any water coming out the return hole near the top after about 5 minutes running. Should I be worried?? How can I assure myself that the cooling system is functioning??

Thanks in advance

 

[Mi duckdown]

Re: Waterpump Question

Need to drop the lower unit and change the water pump impellar. At least.

 

[Texasmark]

Re: Waterpump Question

+1 on the impeller.

On the hole, are you talking about a tell tale hole on the right rear of the lower half of the engine cowling? Or are you talking about the holes at the rear of the engine below the lower half of the cowling....in the mid section?

If you have a tell tale tube they are easily plugged with dirt dobbers and the like.

If you are talking about the holes at the rear, those are exhaust pressure relief holes provided for the sole purpose of allowing your engine to run properly when the boat is at rest or at slow speeds where otherwise exhaust would have to force it's way out of the engine against the pressure of the water around the LU.

The former should be venting water if not plumbed off the thermostat. If so, it should vent water every time the stat opens.

The latter usually don't vent any water at idle/slow speeds; possibly a little mist or sputtering.

Putting your hand on the block will tell you very quickly if the water pump is functioning. If not you can't keep your hand on the block it will be so hot after running for a short period.

Mark

 

[stopngo]

Re: Waterpump Question

Thank you Mark

It was the first hole you mention I was referring to. You are correct in that it plugs up easily.One blast of compressed air fixed the problem. As for feeling the head for Temperature a big 10 4 on that because that was my thought as well.

It sure is nice though to have the added confidence from those who think alike and I thank for your help.

One more related Question: Is there any point or advantage to replace the pump impeller (if working) just as a routine maintenance or does it fall into the If it aint broke dont fix it category?

 

[Mi duckdown]

Re: Waterpump Question

Change the impellar for piece of mind. 40 bucks and your time. when you don't know when it was last changed, It time to replace. impellars are cheap. Motors not so much.

 

[Texasmark]

Re: Waterpump Question

Thank you Mark

It was the first hole you mention I was referring to. You are correct in that it plugs up easily.One blast of compressed air fixed the problem. As for feeling the head for Temperature a big 10 4 on that because that was my thought as well.

It sure is nice though to have the added confidence from those who think alike and I thank for your help.

One more related Question: Is there any point or advantage to replace the pump impeller (if working) just as a routine maintenance or does it fall into the If it aint broke dont fix it category?

Everyone has their opinion and I am the don't fix............kind of guy. Just open yourself to problems that you may not have had before you started messing with things.

I bought my engine 2 years old in 2004. PO had replaced the impeller. I replaced it this year and it had a "set" in some of the blades even though I spin the engine every once in awhile since it sits for quite awhile between outings. Had no temp problems with it as it was and the tell tale at idle would shoot water a couple of inches below the surface....plenty of pressure.

I boat in clear water and it's fresh.

If you are a guy that spends a lot of time in sandy shallow water, highly polluted water with whatever, or you leave your engine sit up for 6 months or so (guess) you might consider every couple of years. Some guys profess every year. Well maybe that fits their boating style and gives them peace of mind.

I follow the axiom that it's your money, time, and equipment. Your choice.

Mark