Coolant

[macroft1]

Hi.

I have a 9.9 Yamaha a stroke engine which runs fine and expels coolant at a good healthy rate.

One thing i have noticed about the coolant is that at higher revs it also spits out from the hole indicated on the photo.

Perhaps one of you could tell me if this is normal?

Thanks and regards.

Mark.

[ranworthbreeze]

Hi Mark,

It would seem that this hole is used as an indicator that the water pump is working.

Please see this site for similar information.

http://www.yamahaoutboardparts.com/forum2/cooling-water-flow-95-9-9-outboard-th11518.html

Regards

Alan

[Guest]

I have a 9.9 Yamaha a stroke engine which runs fine and expels coolant at a good healthy rate. One thing i have noticed about the coolant is that at higher revs it also spits out from the hole indicated on the photo.

Perhaps one of you could tell me if this is normal?

If that's the pilot hole on your outboard then it should have a continuous flow when the engine is running, even when the engine is just ticking over.

You've said that the engine expels coolant at a good healthy rate though, do you mean from the centre of the prop boss or from "another" pilot hole ?

 

[Wildfuzz]

Sounds like the "tell tale" hole has a partial blockage, use some strimmer cable to give it a clean, mine often picks up a little weed or similar, strimmer cable soon sorts it though.

 

S.

[macroft1]

If that's the pilot hole on your outboard then it should have a continuous flow when the engine is running, even when the engine is just ticking over.

You've said that the engine expels coolant at a good healthy rate though, do you mean from the centre of the prop boss or from "another" pilot hole ?

 

It does have a steady stream from another hole underneath where the cowl sits and this flows out at an angle of around 30 degrees to the motor straight back into the water. As far as I've seen this is the norm for all outboards.

However, water also spits out of the hole indicated on the photo at higher revs but this isn't a steady stream like the other one.

Could it be an overflow or worst - a fault!

Regards.

Mark.

[Guest]

Yes, the steady stream is the genuine pilot hole which is a norm for outboards, being the "telltale" that shows the coolant is flowing through ok, (because the main coolant outlet is below water level, so not visible).

 

This secondary stream from another hole could just be splashing inside the plastic outer casing exiting through that other hole.

Or, it could be a failed gasket or crack in the water jacket, though that would normally be bad enough to make the motor run roughly as well.

The only way to be certain is to either remove the outer casing and run the engine, or perhaps try to look down into that part of the casing with the hood off, with the engine running. You might then see the real source of the additional flow.

[macroft1]

Yes, the steady stream is the genuine pilot hole which is a norm for outboards, being the "telltale" that shows the coolant is flowing through ok, (because the main coolant outlet is below water level, so not visible).

 

This secondary stream from another hole could just be splashing inside the plastic outer casing exiting through that other hole.

Or, it could be a failed gasket or crack in the water jacket, though that would normally be bad enough to make the motor run roughly as well.

The only way to be certain is to either remove the outer casing and run the engine, or perhaps try to look down into that part of the casing with the hood off, with the engine running. You might then see the real source of the additional flow.

Thanks Strowager.

The motor runs ok but is slightly rough and vibrates a little. 

One thing I did notice was when I start it up after it's been stood for a while the stream under the cowl puts a slight film of what looks like oil on top of the water but quickly dissipates then clears up. 

As you rightly say this could be a crack or blown gasket which could also explain the spitting.

All a little worrying but now the season's over I've got all winter to investigate.

Edited October 6, 2015 by macroft1