No Cooling Water Flow - What's the Problem?

[minuteman62-64]

Motor is 30 HP Mariner, vintage 1982. Had a mechanic bring it back to life, including replacing the water pump impeller, this past Spring. We ran it when I picked it up and everything was fine, including a good stream of water from the tell tale while running on muffs.

Brought it home on a carrier - laid down in back of truck. Rolled it into the back yard where it sat on the carrier, upright position, till mid-July, when I put it back on the boat. Finally got all the new cables and everything hooked up last week.

This week, time for a test. When I turned the key it fired right up and idled good. However, no flow from tell tale and after 3-4 minutes and it seemed to be getting hot so I shut it down. Since the mechanic had replaced my thermostat with a used one, I was thinking that was suspect. Removed the thermostat and tried again - same thing. Immediately pulled the cap that covers the thermostat - no evidence of water in that area.

So, I have a motor that ran fine last Spring. The only things that were done were the transportation home, mounting the motor on the transom, hooking up the cables and moving the shift lever back and forth while hooking up and adjusting the shifter cable.

Anything I have done that might have caused a problem? Is the lack of any trace of water in the thermostat housing sufficient evidence that the water is not circulating?

Any ideas where to look for the problem? I'm about at the dreaded (for me, never done it before) "drop the lower unit" stage. However, once I do that I don't know what to look for in the way of a problem. Also, I'd hate to drop the lower unit and later find out that the problem was something obvious, that I could have fixed with out opening anything up.

I may call the mechanic back, but, with a motor this old I have to figure out some of these things myself - so I want to take a crack at it first.

 

[minuteman62-64]

Re: No Cooling Water Flow - What's the Problem?

Sigh! The older I get the more I find out that I don't know. Talked to the mechanic and he gave me a number of suggestions, including making sure the pump was primed. That was the first thing I tried. Turned the water on and squeezed the muffs real hard against the motor housing until I heard water gurgling inside the the housing and it started to come out one of the exhaust ports. Started it up and, bingo. Good steady stream coming out the tell tale. Ran it till the carb ran dry with steady stream out the tell tale and no overheating.

Who knew :redface:

 

[MercMan82]

Re: No Cooling Water Flow - What's the Problem?

However, no flow from tell tale and after 3-4 minutes and it seemed to be getting hot so I shut it down.

If you ran the motor 3-4 minutes without water being pulled into the water pump, I'd suggest taking a look at the impeller. It's possible that whatever amount of water that was in the water pump would be enough to keep it cool, but being that you JUST got it fixed, I'd hate for you to have to rebuild it because the impeller was weakened from those few minutes. Seeing is believing and I'm one that tries to keep away from assumptions. Drop it and take a look. BTW, dropping the LU is a pretty standard thing that you should be doing anyway as a boat owner. The water pump should be changed every 1 to 2 years and the only way to get to it is by dropping the LU. Get yourself a manual for your motor and read through it carefully. Ask questions on here if you have them. That's what this place is for. Good Luck!

 

[CharlieB]

Re: No Cooling Water Flow - What's the Problem?

15 seconds at a fast idle is enough to smoke an impeller.

If you can't be SURE, look and see.

Cooling on the hose can be misleading, the hose pressure can 'assist' the water pump, the motor can still overheat once in the water.

Links to service manuals are somewhere in the 'sticky posts' at the top of this forum, find yours and follow the directions, look at that impeller and be SURE before you head out on the water.

Don't want your first time out to be a poor experience.