Strange Outboard Overheating Problem

[thomm225]

Originally Posted by sailjumanji

Since the oil light was on, did you check the oil?

Motored back 5 hours with no oil light coming on, but I'll check it today maybe.

I was tired and it was celebration/beer time when I got the boat back into the slip.

Actually the celebration started maybe 45 minutes to an hour before that when I saw I was going to make it all the way back.

[discoveryawaits]

Originally Posted by atoll

quite often tell tale tubes get blocked by salt if not in use this can dissolve once the outboard is run for a bit but sometimes will need a wire pushing up it to clear it

my Yamaha 20hp had a sticking thermostat it’s only cooling was via the tell tale this works fine for tick over but got hot and rough as soon as you turned the power up

[thomm225]

So I started the engine last night after work and gave it a nice salt water flush! It did fine.

It was too windy, rough, and rainy at the dock to mess with hooking up that adapter etc for a fresh water flush. Plus the boat is in bow too as usual

Guess I'll just keep testing a bit more...…..

Thanks for all the input.

[Mike Banks]

Overheated outboards can happen--usually lack of coolant--which is why I like them air-cooled and small--easy to lift.

Lack of water means a blockage, either in the water intake or in a corroded interior where the varnish has failed in the water galleries around the engine cylinder and head. That happened to me with a Yamaha 3 hp. I failed to notice there was no water coming out of the coolant exit hole. Excrescences of aluminium oxides and hydroxides had blocked the outlet orifice.

The other cause is a damaged impeller caused by some small foreign body damaging the blades of the rubber impeller.

Both require the dismantling of the engine--but fortunately it is not a big job. Download the workshop manual for it--it will tell you all you need to know and give any parts numbers you may require-0-and while you are at it, clean the carburettor and reed valve if necessary.

[thomm225]

Originally Posted by Mike Banks

Overheated outboards can happen--usually lack of coolant--which is why I like them air-cooled and small--easy to lift.

Lack of water means a blockage, either in the water intake or in a corroded interior where the varnish has failed in the water galleries around the engine cylinder and head. That happened to me with a Yamaha 3 hp. I failed to notice there was no water coming out of the coolant exit hole. Excrescences of aluminium oxides and hydroxides had blocked the outlet orifice.

The other cause is a damaged impeller caused by some small foreign body damaging the blades of the rubber impeller.

Both require the dismantling of the engine--but fortunately it is not a big job. Download the workshop manual for it--it will tell you all you need to know and give any parts numbers you may require-0-and while you are at it, clean the carburettor and reed valve if necessary.

Yeah, I've replaced the impeller 3X times over the past 7 years.

I ran the engine again today for 20 minutes at the dock and it was pumping water and ran fine.

I've had like 8 outboards so it's not a new thing to me. The new thing was that it started to work again a few days after overheating when I did nothing to repair it.

I even sailed in to a spot where my son could bring me tools to repair it. Unfortunately the winds were close to 20 knots at the anchorage so I decided to do the work in the am when the wind were predicted to be 5 knots.

That morning, I decided to start the engine before I took it apart to know for sure it's state and it began to pump water so I motored off anchor after 10 minutes and then motorsailed 5 hours back across the bay to my slip

[HopCar]

Originally Posted by thomm225

Yeah, I've replaced the impeller 3X times over the past 7 years.

I ran the engine again today for 20 minutes at the dock and it was pumping water and ran fine.

I've had like 8 outboards so it's not a new thing to me. The new thing was that it started to work again a few days after overheating when I did nothing to repair it.

I even sailed in to a spot where my son could bring me tools to repair it. Unfortunately the winds were close to 20 knots at the anchorage so I decided to do the work in the am when the wind were predicted to be 5 knots.

That morning, I decided to start the engine before I took it apart to know for sure it's state and it began to pump water so I motored off anchor after 10 minutes and then motorsailed 5 hours back across the bay to my slip

Sounds like you picked up a plastic bag or some grass that temporarily blocked the intake. A little extra wear on the engine but ok for now.

[thomm225]

Originally Posted by HopCar

Sounds like you picked up a plastic bag or some grass that temporarily blocked the intake. A little extra wear on the engine but ok for now.

I hope it was that.

The engine down by the prop was bouncing in and out of the water a lot for two days so it's very possible that cleaned off whatever was blocking the intake.

This engine has taken a bit of a pounding. This is the second time it's over heated. I actually caught it early this time because it hadn't started missing or sounding strange yet like the last time.

Last time I was in traffic in the creek 600 yards from my marina and had to raise sail to avoid hitting docked boats or Navy Landing Craft.

I anchored for a while and got a tow to the T dock. Then let the engine cool some more, removed the cover, started the engine, and put the boat in the slip