1998 Yamaha 200 HP Poppet Valve

[Atifawan]

Hello Guys,

I have a couple of relatively old 200 HP Yamaha 2-Stroke outboards (1998) and one of them is overheating at low RPM (even idling). After doing some basic research on this forum and on internet in general I believe the culprit here is the poppet valve (pressure relief valve). However, I am unable to find the exact part number that I need as when I look at the 1998 outboard parts list none of the components have the poppet valve listed under it. Can someone help me in identifying which Yamaha part number I need for replacing this valve?

Regards,
Atif

[jiggin joe]

re valve Pressure Control

What is the model no. of your motor?

[99yam40]

1998 200TLRW Yamaha Outboard CYLINDER CRANKCASE 2 Diagram and Parts

[robert graham]

That Pressure Control Valve(Poppet) is very simple, spring, black plastic piece, and black rubber grommet. Easy to replace. I changed mine recently and it did have a good bit of mineral/corrosion deposits in and around it, which could have caused sticking. I cleaned up the old one with some acid and it looked almost new...so now I have the old one for a spare! Good Luck!

[Atifawan]

Thank you for the feedback guys and for sharing the relevant outboard schematic. I was looking for a part with a name like 'poppet valve' or 'pressure relief valve' so I guess I just fooled myself :-).

Just an update, I did open the valve up today and found out that it was not too bad. On further investigation it appears that water is not reaching the top of the engine (where the thermostats reside) and the mechanic suspects it could be an impeller issue. Will have the impeller looked at tomorrow and hopefully it will not be something serious.

[rodbolt17]

a sticking or leaking pressure control valve will give this exact symptom.
does it only overheat at low speeds or at any speed?
and its not the valve its the grommet that gets corrosion under it and sticks the valve.

[Atifawan]

When we took out the valve I did see the plastic valve and the compression spring but the grommet did not come out. Can the grommet stick to the internal casing and if it does then is that a cause for concern?

I have not run the engine at higher speeds as I shut it down soon after the alarm thinking I may damage it. The guys here opened up the thermostat housing and then started the engine and we did not see any water being pumped up. Is that a valid test methodology or will a sticking grommet result in similar symptoms?

[robert graham]

That grommet has a groove in it that fits over the aluminum opening...gently loosen and lift the grommet out with a small screwdriver or some needle-nose pliers...it's most likely just stuck with mineral/corrosion deposits. Clean it all good with maybe wire brush, toothbrush, 3M Pad, etc., then install new grommet.

[Atifawan]

Thanks Robert. I do not have much experience with outboards so am asking too many questions :-). Can you offer any advice on no water coming out of the thermostat housing with the engine running? Can it be attributed to a stuck grommet as well or should we look at the impeller for that?

[robert graham]

Thanks Robert. I do not have much experience with outboards so am asking too many questions :-). Can you offer any advice on no water coming out of the thermostat housing with the engine running? Can it be attributed to a stuck grommet as well or should we look at the impeller for that?

I can't say for sure about that, but Rodbolt is the real Expert here and hopefully he will offer his thoughts. How long since the Water Pump was replaced?...usually need replacement every 2 or 3 years, but always Before they fail! Water Pump replacement is a fairly simple job(I did mine, and the parts(on line) are pretty cheap(about $50). Good Luck!

[Atifawan]

Thanks Robert. The impeller was replaced an year or so ago. I will have it checked out anyway. By the way this forum is great with a lot of people willing to help newbies like us. I hope I can give something back in future.

[robert graham]

Google: Yamaha Maintenance Tips Andy, for instructions with photos for water pump replacement plus several other maintenance/repair procedures...very helpful information!

[Atifawan]

Just wanted to update you guys on our finding today. We ended up opening the lower casing and found out that the impeller was toast. A small part of it had actually melted and ended up blocking a good part of the water intake. I am not sure how it happened but maybe a polythene bag cut off the water supply to the impeller momentarily ending up in this situation. We replaced it and the overheating issue has disappeared.

Before opening the impeller I was playing around with the grommet, trying to get it out and I think during this exercise it actually fell into the casing. I am going to put in a new grommet tomorrow and for now have decided to leave the other one inside. Do you guys see any issue with that?

[robert graham]

It may or may not hurt anything, but if it was me, I'd be trying to get it out...

[rodbolt17]

it will overheat.
fish it out with a bent coat hanger.
its fallen down and to stbd.
it cant go to port.