Mariner 70 hp thermostat/poppit valves

[bluenoseboater]

Hi there,

I am wondering if my 1982 Mariner 70 hp, 3-cyl, S/N 6228858 has a thermostat and/or poppit valves? When connected to the earmuffs, I ran it several minutes and got no stream from the tell-tale. The engine seemed to be getting pretty hot so I shut it down.

When running, there was a significant amount of hot water leaking out between the upper drive shaft housing and the lower gear housing. I removed the lower unit and discovered there is no gasket here. I have read in some posts that it is not unusual to see some leakage at this joint but excessive leakage may mean a problem with the water tube not being seated properly, or obstructed.

I disassembled the water pump and found one vane missing. The rest are intact. I ordered a complete water pump kit which I plan to install as soon as I get it. Before reassembly, I am wondering a few things:

1) Where did the missing vane go? Could it be lodged somewhere in the cooling system and causing an obstruction?

2) Does this engine have a thermostat and if so, where is it located? If it has one, I'd like to remove it and test it.

3) Where is the poppit valve(s) located? Should I be looking at this?

Any help much appreciated. I want to be sure my cooling system is up to snuff before starting the season.

Thanks,
Wade

 

[ajgraz]

Re: Mariner 70 hp thermostat/poppit valves

On those mid-70's to mid-80's Merc/Mariner 3 cylinders...

No tstat or poppets.

A little leakage between drive shaft housing and gearcase housing is no big deal, so long as all your LU mounting hardware is on and tight. There is no gasket there. That water isn't going to intrude into the LU lube. Do check that the seal at the bottom of the exhaust tube looks good, though.

Your missing vane would have caused the impeller not to pump well, and is likely in there restricting flow (as you suspect). It is in one of two places:
1) Up the water tube; get it out by backflushing with a hose through the brass fitting at the top of the powerhead/jacket (the fitting that leads to the peehole). BTW, there should be no significant restriction to water (or mouth-blown air) between that brass fitting and the water tube; if there is then you could have some serious blockage or salt/scale/corrosion crustage in the powerhead.
2) Down in the LU between the pickups and the pump; get it out by removing the LU, removing the entire pump and baseplates, removing the plastic pickup screens near the foot, and flushing through with a hose. If this hasn't been done in awhile, there's likely decades' worth of itty bitty impeller pieces in there.

As to the pump: original or older-style pumps require a rubber seal (looks like a short piece of tube) and a cup washer (looks like a plastic end-cap with a hole in it) at the bottom of the water tube to mate with the pump housing; if the hole in the pump housing is considerably larger than the tube, this is what you have. Newer replacement pump housings have superceded the original, they snug right onto the water tube with no need for the seal and cup washer.

EDIT: Did anything come out of the peehole? Even just some steam or a few drops?

EDIT 2: Make sure you have the impeller shaft key in place, or the impeller will not turn.

 

[bluenoseboater]

Re: Mariner 70 hp thermostat/poppit valves

Thanks ajgraz,

I did remove the intake screens and checked the passageway from here up to the water pump. It's wide open and clear. Also, my rubber gasket where the exhaust tube fits into the lower unit looks in good condition.

I will check between the brass fitting in the powerhead and the water tube by backflushing/air as you suggest. If there is any significant restriction there, I'll have to get it cleared out.

There were a few minor drops from the tell-tale, as well as a bit of steam/smoke. I did not let it go too long for fear of overheating and damaging the motor. I suspect between the weak water pump and the leakage between the upper/lower housing, I would not get much of a stream from the tell-tale.

Thanks for the information on the thermostat and poppets. Will let you know what I find out on the restriction and performace with the new water pump.

Thanks,
Wade

 

[Maxz695]

Re: Mariner 70 hp thermostat/poppit valves

Today I removed my complete waterpump in hopes of receiveng what I paid for, a complete waterpump (What i receved was a partial repair kit (RRRRRRRRR) anyway what I found was disturbing, I replaced the impeller less than a year ago. I did not greese the impeller. I had very poor flow through the tell tale before dismantle. I tryed 2 times to clean and reinstall the outdrive with no luck.(Which is why I bought a complete Waterpump kit)Upon further inspection in removing the entire water pump base plate and all, I noticed something that I wouldn,t think would be the problem in the first place. Being the entire impeller was there in tact and seemingly perfect with minor bends to the vains, I inspected just a bit further and BANG!! there it was. I took my little pinky and stuck it inside of the impeller. AWWWWWWWWWW this is to easy. the dang center cylinder turned like it had butter in it. Who woulda guessed. the center was turning and the outter rubber went NO WHERE!!!!! Lesson learned. The sad part is I totally destroyed my baseplate trying to get it out thinking a new one would show up in the mail. I guess I,ll just have to post at least another week waiting on the new one!