Mariner Cooling Water Flow Path?

[minuteman62-64]

Finally got the boat w/30 HP Mariner (1982 vintage) in the water today. Ran great for awhile, then started overheating although there was a strong stream coming out the tell-tale. Limped back in by stopping to let it cool down, then restarting and making some more headway.

Hopefully no serious damage - I'll start by checking the compression this weekend. Then I want to approach the cooling problem logically. The water pump impeller is new - less than two hours on it. I didn't do the work, so I can't guarantee it was done properly, however, I'd think the good flow out the tell-tale indicates it is OK. So, I'm thinking I'll look at the thermostat first.

This leads to my question. Does the cooling water in this motor flow past the tell-tale and then through the thermostat, or, does it flow through the thermostat and then past the tell-tale?

If it turns out I've actually fried the motor this is a moot point. But, I'm an optomist, and want to think that I can get it running properly again.

 

[minuteman62-64]

Re: Mariner Cooling Water Flow Path?

Checked the compression today. #1: 148 psi; #2: 145 psi, both taken cold. I previously checked the compression cold back in September and each cylinder had 140 psi. Can I assume I dodged a bullet w/regard to major engine damage?

Next I'm going to try running it w/o the thermostat and see if that makes any difference.

 

[minuteman62-64]

Re: Mariner Cooling Water Flow Path?

OK, pulled the thermostat and, just on a whim, started it up with the thermostat cover off.

After about 10 seconds water began flowing from the tell-tale. However, nothing from the open thermostat housing. Shouldn't water come shooting out there by that time if the pump was working properly and there were no clogs in the passages?

I would have let it run longer, but was afraid of doing damage. Then I realized that I had run it a lot longer yesterday, in the same condition, while limping to shore. Monday I'll try it a little longer, again with the thermostat cover off, and see if there is any water moving through the thermostat housing. If not, any suggestions on the next step?

 

[Sunfish12]

Re: Mariner Cooling Water Flow Path?

There could be a clog down at the base gasket area. Do you know if the old impeller was disintegrated?

 

[minuteman62-64]

Re: Mariner Cooling Water Flow Path?

There could be a clog down at the base gasket area. Do you know if the old impeller was disintegrated?

I didn't do the impeller replacement so I don't if it was disintegrated. It was 20 years old, and I had pulled the rope starter a couple of times before I took it in for service (wanted to see if it was capable of being brought back to life), so it would have been very brittle and there is a possibility I knocked a few pieces loose. However, I would think the guy who did the service work would have cleaned that stuff out as a part of the job.

Where is the base gasket area? Does this mean I'm at the ".... drop the lower unit" stage?

 

[Sunfish12]

Re: Mariner Cooling Water Flow Path?

The base gasket is where the engine block bolts on. When the waterpump was replaced they probably ran it and saw the tell-tale working and figured it was good. You can try to probe down the thermostat hole with a coat hanger to break up any blockage.

 

[hl]

Re: Mariner Cooling Water Flow Path?

Reading this forum I wondering if the water passage can be flushed out by running water into the stats and back down to the foot.

 

[minuteman62-64]

Re: Mariner Cooling Water Flow Path?

Reading this forum I wondering if the water passage can be flushed out by running water into the stats and back down to the foot.

I don't know. If (when I try starting it up again) there is no water at the thermostat housing (which in my motor is at the top of the block) I'll be trying just that. Maybe some compressed air also. Seems like it would be best to be doing that with the lower unit pulled, so if there is crud that gets dislodged it can be removed.

 

[Sunfish12]

Re: Mariner Cooling Water Flow Path?

Yes, lower unit removed is the best way. If you do drop the lower unit you can probe up the water tube also.