Reviving a non starting 8HP Yamaha OB (and related quesions)

[ProDave]

Our new to us boat came with an 8HP 2 cylinder electric start remote control OB (in a well) except it would not start. It's now on the bench for investigation, I should be ready to try starting it tomorrow once I have done preliminary things like new plugs, new oil, and rigged up a tank for it to run in.

In advance of that, is there any way from the serial number to determine it's age? The numbers as they appear on the name plate are:
Yamaha 60R
F8CMH
S 1011435
J

 

[William_H]

The simple first trick is to examine the spark plugs after trying to start for a few goes. If the plug internals are wet with fuel then you probably have an ignition problem however if plug is dry then a fuel problem. My apologies if you know this already. ol'will

 

[QBhoy]

Would it not start…as in, will turn over by the starter and pull chord…but not fire up ? Or not start, as in physically won’t turn over at all ?
Outwith anything caused by obscene neglect or mistreatment, odds on to be a fuel related issue, if it is actually turning over. Id firstly take the plugs out and check for colouring and even water. Check the oil isn’t diluted and correct level. She’ll likely have a low oil alarm or even interlock. Speaking of interlocking…don’t hate me for asking the obvious questions like…is the kill switch lanyard in place ? Is it in gear and perhaps has an in gear safety switch (most modern models do, of a certain size).
Back to non obvious things. Make sure she’s getting fresh fuel to her. Flush the fuel system by bowl drains. Prove the presence of fuel to the last possible stage. At filter too. Make sure the primer bulb is drawing fuel and not air. Make sure its arrow is the right way too. Check the fuel line ball valves/nr valves. Obviously don’t even entertain any attempts, with anything but fresh known fuel. All that stuff…etc etc.

 

[ProDave]

When it was in the boat, it was turning over, and occasionally coughing like it was trying to fire, but not running. We had few tools and access was poor so checks were limited. The ignition was seemingly okay in that if you took a plug cap off you could get a spark from it but could not take a plug out.

Fast forward to now it is on the bench, Oil drained, thick black gloopy horrible oil, fresh oil fitted. Plugs were black with a massively wide gap. New plugs fitted. Fuel is visible in the fuel filter and fuel appears to be in the carb float chamber.

When I get back from some work I have to do this morning I will rig up and fill a test tank and try it.

Any ideas how I can tell from the numbers posted above how old it is?

 

[ProDave]

Well this is going to be a shorter thread than I expected.

It pretty much started first turn of the key. not even much choke needed.

To start with it was not peeing from the teltale, except just a dribble when you revved it. Unscrewing the flushing hose and it was pumping water out of that so the impeller must be pumping. I cleared out the teltale rubber pipe with some stiff wire and now it's peeing okay even at idle.

Seems to be running smoothly, able to deliver power when demanded (as much as I can in a small tank) idles nicely, no leaks from anywhere.

So I guess it was just the plugs.

Now I need to give it a good clean up, sort out a tool kit to go with it, and an emergency starter cord and it can go back to the boat.

 

[ProDave]

So this is an unknown age, probably old engine. What preventative maintenance should we be doing? One obvious one for me is camshaft belt. Very important things on a car. This motor has a short toothed belt, without even any visible form of tensioner. You don't want the belt to let go, even if it does not destroy the engine, it would stop it working, so is this an easy job to do?

 

[Tranona]

2012/3 This may help

en.impex-jp.com/catalogs/outboard/yamaha/f8.html

No clever inside knowledge, just a quick google!

 

[ProDave]

2012/3 This may help

en.impex-jp.com/catalogs/outboard/yamaha/f8.html

No clever inside knowledge, just a quick google!

Thanks, so about 10 or 11 years old, not as old as I thought it might be.

 

[ProDave]

I see the manual says just to inspect the timing belt and only replace when it shows signs of cracking or worn teeth. I guess it's not under much load then.

Leg anode has almost disappeared, time for a new one.

The leg of this OB has been painted with antifoul. I think the previous owner kept it down all the time, though on this boat it should lift and slide up into the well, so no need for that. What's best to di with this? re paint it in antifoul or try and strip it back to bare metal and paint with something more appropriate?

 

[Dellquay13]

Do you get much cooling water exiting through the prop?
With an unknown engine used in saltwater I would give it a good long flush with freshwater, about an hour, and if I could introduce some descaler all the better. The telltale might be clear now, but the rest of the head might still be very constricted. AFAIK the tell tale is quite early on in the water path around the engine and is more a sign of a healthy impeller than good cooling flow through the rest of the head.

 

[ProDave]

I am almost ready to put this motor back in the boat, but wanted to check one more thing before I do so, and that is that cooling water is circulating everywhere it should.

I have run it again today, but this time not immersed in a tank, but with water supplied by a flushing muff that cups over the water intake points on the leg and supplies water from a hose.

Running it like this, it is clear that water enters at the bottom of the leg where there is a grille each side, now covered by the muff. When the engine us running water discharges from the telltale pee hole, and also a mixture of water and exhaust gasses exit through the middle of the prop. (that bit is not obvious to see or check when running it in a tank)

I can't find anything documented stating where water should exit when all is well, so just wanted to check this is correct and it should not be coming out anywhere else (and indeed should be coming out where it is)

I ran it for about half an hour and all seemed fine.

 

[penfold]

Sounds normal, not all motors have an telltale but it's more or less universal to have most of it exit along with the exhaust.

 

[VicS]

From the tell tale but the main cooling flow exits with the exhaust.
You'll probay also get a few drops or a .mist blown out of the back pressure relief port on the leg .

Muffs are good for flushing an outboard but in a tank is better for testing because muffs supply water under pressure and might mask poor pump performance