Yamaha 9.9 4T oil consumption

[pakostane]

I am going to clean all head, and top of pistons but you give me good idea to soaking piston rings with some sort decarbonizer.

[pakostane]

I changed valve seals, head gasked and put new thermostat but oil consumption did not reduce. Cca 10h 0.5L of oil. I think I need to replace piston rings.



On drawing there is only plane bearing. Is there some connecting rod bearing?

[TownsendsFJR1300]

Looking at your parts picture and this one (close to yours):

2004 F9.9MLHC Yamaha Outboard CRANKSHAFT PISTON Diagram and Parts

It appears there isn't separate rod bearings. . The rod IS the bearing Just crankshaft bearings.

**Looking at other larger engine parts fisch', it seems most don't use connecting rod bearings until the 25 hp models and up.

My two 10HP, non marine engines (generator and chipper / shredder) do not have separate bearings. Neither did a much larger Yamaha power-washer where the rod bolts loosened up (pump pressure relief valve failed) and destroyed the rod, crank, etc.

[pakostane]

Is it possible to change piston rings from bottom side without head disassembly?

[TownsendsFJR1300]

Is it possible to change piston rings from bottom side without head disassembly?

You most likely would break a piston ring going back in as there's no room to compress the rings into the bore..

It's MUCH EASIER to pull the head and install pistons and rings from the top. A ring compressor is also needed besides cylinder honing...


I don't have a shop manual for your engine but looking at the parts fisch (similar to yours):

http://www.boats.net/parts/search/Ya...ASE/parts.html
it appears you don't have to remove the engine from the mid-section.

Access to the connecting rod nuts is possible with removing the front cover (opposite end of the engine-lower end / plate of the block)

[pakostane]

I just fixed up head with new valve seals and head gasket. I will eventually try decarbonate oil rings with some oil aditive or just top up oil during usage.

[TownsendsFJR1300]

I just fixed up head with new valve seals and head gasket. I will eventually try decarbonate oil rings with some oil aditive or just top up oil during usage.

Yamaha dealers ONLY have access to a Yamaha product that is put in the cylinder(s) and left (I believe overnight), that OFTEN breaks up the carbon.

Reading on this forum, per Rod Bolt, it works very well....

[pakostane]

I don't have a shop manual for your engine but looking at the parts fisch (similar to yours):

2004 F9.9MLHC Yamaha Outboard CYLINDER CRANKCASE Diagram and Parts
it appears you don't have to remove the engine from the mid-section.

Access to the connecting rod nuts is possible with removing the front cover (opposite end of the engine-lower end / plate of the block)

I am not sure, I think I have to remove engine from mid section. You can not remove front cover without remove engine from mid section.

[pakostane]

Yamaha dealers ONLY have access to a Yamaha product that is put in the cylinder(s) and left (I believe overnight), that OFTEN breaks up the carbon.

Reading on this forum, per Rod Bolt, it works very well....

I notice some oil on sparks thread. The same on all two sparks. Is it possible that oil rings on all two pistons stuck in carbon?

[TownsendsFJR1300]

I personally would try having the dealership perform the chemical treatment first.

Certainly can't hurt and a bunch easier than a full tear down...

[rodbolt17]

I belive the product from Yamaha is called YIES.
I use it all the time.
stuff works very well.
in fact I have a pair of F350 motors I am going to use it on next week weather permitting.
most the leak down numbers are in the 50-65% range.
once I use it I will post the results.

[TownsendsFJR1300]

I notice some oil on sparks thread. The same on all two sparks. Is it possible that oil rings on all two pistons stuck in carbon?

I'd like to see a pic but if your burning that much oil, sure...

You don't know the history of the engine.

The rings, with the oil usage, should look pretty black and oily.

You can try a SHOCK TREATMENT of Yamaha's RingFree (2 oz / 1 gallon) for 6 gallons and see if it helps.

IMO, it is a great product and works well but depending on how much carbon is in there, ????

[TownsendsFJR1300]

I belive the product from Yamaha is called YIES.
I use it all the time.
stuff works very well.
in fact I have a pair of F350 motors I am going to use it on next week weather permitting.
most the leak down numbers are in the 50-65% range.
once I use it I will post the results.

Thanks. And that is NOT available to the public, correct?

[pakostane]

I'd like to see a pic but if your burning that much oil, sure...

You don't know the history of the engine.

The rings, with the oil usage, should look pretty black and oily.

You can try a SHOCK TREATMENT of Yamaha's RingFree (2 oz / 1 gallon) for 6 gallons and see if it helps.

IMO, it is a great product and works well but depending on how much carbon is in there, ????

When I put down head I cleaned all cylinder head and poston forhead. I could not see how ringh looks like.

[pakostane]

I'd like to see a pic but if your burning that much oil, sure...

You don't know the history of the engine.

The rings, with the oil usage, should look pretty black and oily.

You can try a SHOCK TREATMENT of Yamaha's RingFree (2 oz / 1 gallon) for 6 gallons and see if it helps.

IMO, it is a great product and works well but depending on how much carbon is in there, ????

https://www.amazon.com/Yamaha-Yamalu.../dp/B002GU4SN2

Is it aditive for decarbonate rings?