My Mercury Runs Hot?

[Yellowstone]

Should it the tell tale get pretty hot on a 1969 110, 9.8 hp? I recently had the water pump replaced at the marine shop as I’ve only worked on Johnson and Evinrude’s and spending most of my time restoring my Alumacraft FD that accompanied the motor when I bought the combo. Anyway, it still runs hot after the replacement at full throttle and lukewarm at idling and low speeds. It cools down pretty quick when I lower the speed but it concerns me a bit. Should it even be warm at any speed, I don’t know Mercury’s much at all. I ran the boat and motor at various speeds tonight for half an hour and everything performed well except that tell tale.

[need2fish]

The telltale stream should be warm but not enough to scald you.

If it is really hot, it’s possible the old impeller had lost bits of its vanes, which are now lodged in the cooling system somewhere. At idle enough water passes through to cool the engine, but not enough to do it at high speed.

Another possible cause is the water tube seal where the tube enters the powerhead is damaged or missing.

[fleetwin]

Hopefully a Merc guy will chime in here….I can reply when it comes to the OMCs, but not the Mercs…
It all depends on where the indicator is tapped into the engine.
On most OMCs, the indicator tap is located on the exhaust manifold, which is at the beginning of the cooling cycle. So, the telltale flow should never get “hot”, it should always be pretty cool, perhaps a bit warm in this hot weather.
That is a nice old Merc, so let’s wait to hear from a Merc guy, you wouldn’t want to harm such a nice engine.

[Yellowstone]

Thanks need2fish and fleetwin. The marine shop I go to for all my supplies like gear oil, grease, and such, thought it was running good after they made the repairs and ran it in their tank. They barely charged me anything to replace the pump. They looked it over and found leaky fuel lines and replaced those and “made” new nipples as they couldn’t find those parts any longer. And they replaced the kill switch. Told me the gear oil looked great. I knew the previous owner had just changed. I suppose I could ask the shop too but they really aren’t specialists in older motors, just newer Mercs.

It is a beautiful motor. I bought the boat for the boat but I really like the motor. It runs like a rocket, especially if it’s just 1-2 people. But it trolls down nice to next to nothing too.

[billw]

That IS a nice one! The tell tale on those is plumbed a lot more towards the outlet end of water flow than it is to the inlet. The way you describe the water temp makes sense to me.

Long live American manufacturing!

[Yellowstone]

Thanks BillW. My son and I taped everything good, scuffed, sanded and rattle canned everything above that 9.8 decal with original mercury phantom black. Not a perfect job but it looks great. It was pretty nicked up up top at first.

[fleetwin]

Nice paint job, thanks Bill for chiming in….
Enjoy that great engine

[The Boat House]

• This reply was modified 3 years, 10 months ago by The Boat House.

[Yellowstone]

Thanks fleetwin and tubs. There were lots of nicks and scratches down to the original primer. It was OK as is but thought I would try a simple “touch-up.” In reading the Mercury paint can, I realize we could have, should have used a clear coat on top for best results. But we’ll see how she does. Right now, it sits on a lift and I use an old Weber kettle cover cinched down over it to protect the top half from the sun and rain. Here are a few more pics of the motor and boat. From the back and the inside paint job we did. Re-riveted where necessary. Then expoxied all the floor rivets and seams with Gluvit and then two coats of primer and 3 coats of non-skid rubberized Tuff Coat. I’ll tell you, drilling out all those aqueduct transom rivets was a careful, tedious job. They were replaced with stainless steel bolts, washers and lock nuts.

[fleetwin]

Perfect size rig, and that merc will power it with ease….
Now get out on the water and enjoy it!!

[Author]

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