rodbolt - help!

[blairmcgrath]

You seem the best credentialed person on here (no disrespect to others), and I am starting to fear rhe worst for my 1989 Yam 70hp (I think 70ETLF). Can you tell me do these motors have a system that shuts down cylinders as a safety precaution if somethings not right? Can the alarm itself shut down cylinders?

[rodbolt17]

yes, they do.
what seems to be the issue and when does it start?
the 70 uses a low pressure high volume system.
its why fresh pump kits are always nessasary.
it can also go into RPM reduction if the oil tank is low or the switch fails.

[blairmcgrath]

Seems to idle ok - but only steam comes out pisser. Then when you full throttle, the engine starts missing badly, yet the water is squirting out the pisser hard - except its hot. All the while the alarm is sounding. Water pump seems fine to me, impella rubber is in good condition, housing ok. I have found that the thermostat has corroded away, but I wouldnt have thought that would cause all this

[99yam40]

Can you give a little history on the PM on this motor?
What all have you done to it in the last few years and what all have you done since the problem popped up?

[rodbolt17]

99yam40
PM me

[blairmcgrath]

I had noticed recently that the anode has corroded away. In terms of any maintenance - internally I have only changed spark plugs - the impella is the same since I got the boat (and is in good shape). Of course I always flush motor with fresh water after use. The anode issue worrys me - could corrosion have got into motor. 1 other issue - my motor is a 1989 70BETO - I am in Perth, Australia and my local Yamaha dealer reckons these motors are different from US ones - diff electrics and everything. That surprised me - doesnt Japan make them then send them all around the world, shouldn't mine 1989 (70BETO) be the same as yours 1989(70ETLF).
Since prob has arisen I have gotten into exhaust chamber of motor (thermostat corroded away) and Dismantled water pump. Yam dealer suggests checking the head/gasket next

[99yam40]

I would recommend replacing the water pump and thermostat as they are normal preventative maintenance and it does not take much wear to cause problems with water flow.
Not sure if that motor has a PRV(pressure relief valve) or not but if it does check/replace it and clean up any corrosion around it as that will cause a low RPM overheat if it sticks open and dumps too much water
If you have a lot of corrosion inside the motor you may need to pull head and clean all water passages

[rodbolt17]

like I said, low pressure high volume system. means no pressure control valve.
you CANNOT assume an international market engine is the same as the US market engine.
typically they are similar, in some cases identical and in some cases totally different.
some clean pics of the powerhead may help.
myself I would have the head and exhaust apart as well as replacing the complete water pump and the T-stat and whatever parts are to corroded.
assess it once its apart and see if its worth fixing then make a plan and go.
if you half job it then you have exactly what you paid for.

[99yam40]

Rodbolt you have a PM

[rodbolt17]

arrite
taken care of

[blairmcgrath]

Well, well, well guess what I found, The head was absolutely full of crud, so there was no water cooling being done there, so now I am back in business. Incidently Rodbolt, you said US models and overseas models are not always the same which is fair enough. In this case my 70BETO and the 70 ETLF seem identical in all diagrams. The prices on here are noticably cheaper than at home. Should I have faith in the 2 types of motors parts will be the same, given they look the same in pictures?

[rodbolt17]

cross check the part numbers between the international stuff to the US stuff.
the first 3 characters ID what model the part was first used on,the next 5 id the part,the next two are engineeering revisions and the last two are paint codes if painted.

[blairmcgrath]

The only numbers that I can find are the the serial No.= 6H3 L 457289 (on plate affixed on outside of motor); the Block itself= 6H304 Y-1; the Head= 6H3 00; the Exhaust cover= 6H3 01; the thermostat= 6H3 1. So my Aussie 70BETO are all 6H3 numbers and the US 70ETLF are 6H3 numbers also. So does that mean the parts will match? Or do the extra digits on the end change things?

[rodbolt17]

not usually, but do you see the pattern?
the part number are patterened as well.
if you have access to the international numbers you can cross them with the US numbers.