Rich / Help Please

[Tonka Jim]

Hey Rich,

I had a strange thing happen yesterday when I was putting the 174 to bed for the winter.
'68 120 with pre-Alpha drive.
Hooked-up the 'Fake a Lake' and ran ran it to temp.
Drained engine oil & out drive lube, refilled both, new oil filter.
Fired it up to fill oil filter & no water to engine 
Pulled & checked thermostate - open but no water in housing.
Pulled plugs to drain engine & manifold.

What could have happened to my water circulation.

[Rich_V174SS]

Sounds to me like you might have fried your pump impeller in the drive, that would be the first thing I check. Was it pumping when you first ran it up to temperature? Sometimes if the ear muffs are not positioned properly on the intake screen you might not get any water going into the pump. The hose water should be on full too. I had a similar problem with my old Merc 120 too, turned out the impeller rubber broke free from the brass hub and wasn't pumping any water. I changed the impeller and that solved the problem. Of course though to check or change the pump impeller you have to drain the oil in the drive again to separate the drive halves.

Disregard the arrows in the pic, that was for something else. 

[Hyperacme]

Yesterday when I did mine, the tail tell would run strong then skip a beat ...
Repositioned the muff and got a strong steady stream.
Weight of the hose/vibration of the motor must have made it slide around ...
Replace your impeller with a Merc part for peice of mind !
Do you know the last time it was replaced ?

[Tonka Jim]

Muffs were in proper position for both runnings.
I guess it was just time for water impeller to fail.
I'm happy it was in my driveway and not in the middle of the lake.
Impeller has seen 3 seasons, maybe it was just it's time.

Do you have a Merc. part number for the impeller kit?
I do not want to use an after market impeller.

[Rich_V174SS]

Here's a link to water pump kits, the first item also includes the pump housing and is often a good idea to replace that too. Also see the third item for the pump base. The base also contains a shaft seal so water doesn't get into the gearcase. If you have the original 60's style base it could have a flush-port hole in the side of it, if it does I would change it out for a newer style which doesn't have the hole. Mine had this hole and I found out most of the pumped water was exiting this hole and just coming out through the prop with exhaust because it wasn't plugged properly, limiting the amount that was actually getting to the engine.

http://www.sterndrives.com/waterpumpkits.html

[Tonka Jim]

Thanks Rich,

My '68 V174 had the old 120 drive on it with the flush port.
I updated to a rebuilt 'R' style from the mid 70's about three years ago so I don't think that's a probleme here.
I will be ordering the 'Water Pump Kit' and the pre-Alpha base.

Thanks 

[Tonka Jim]

It looks like I was lucky this time

No overheating at the pump, upper housing, stainless insert & lower wear plate in good condition.
All I need is the Impeller, 2 Gaskets, 2 O-rings & Seal.

[Rich_V174SS]

Yep, that's what happens to an impeller when it either gets old or is run without water.

[Tonka Jim]

It was NEVER run without water    and it's 3 years old and still flexable.

Could something have gotten in there and broken the impeller 

[Rich_V174SS]

Please don't misunderstand, I'm not saying you purposely ran it without water. It's just I've seen this happen many times where the hose is hooked up and the water is running but if the water isn't precisely directed into the intake screen the impellers can fall apart in as little as 10-20 seconds if run "dry". Also, being 3 years old it was time for a new one anyway, I'd say 2 seasons is the limit for the older Merc impellers because they can get brittle and sometimes just cranking the engine will break them.