Yamaha Hydradrive - problem

[osprey24]

Hi guys,

Yamaha 4.2 Toyota Hydradrive

Low sea flow pressure alarm going off.
Went out few weeks back and my alarm went off and temp crept up so turned it off and got towed back in.

No messing about pulled engine out and stripped all pipe work and sent heat exchangers off to be cleaned.

Whilst checking pipe work I found bits of a old anode in the steering oil cooler section of pipe work. So cleaned it all out and didn’t see anything else to worry about.

Boat back in the water today and I have the same problem, there’s plenty of flow with engine running and take the strainer cap off and the water flows out as you’d expect.

Any ideas ?

Replaced impeller / cleaned pipe work / exchangers cleaned

[beamishken]

Originally Posted by osprey24

Hi guys,



Yamaha 4.2 Toyota Hydradrive



Low sea flow pressure alarm going off.

Went out few weeks back and my alarm went off and temp crept up so turned it off and got towed back in.



No messing about pulled engine out and stripped all pipe work and sent heat exchangers off to be cleaned.



Whilst checking pipe work I found bits of a old anode in the steering oil cooler section of pipe work. So cleaned it all out and didn’t see anything else to worry about.



Boat back in the water today and I have the same problem, there’s plenty of flow with engine running and take the strainer cap off and the water flows out as you’d expect.



Any ideas ?



Replaced impeller / cleaned pipe work / exchangers cleaned

Is it picking up its water from the leg only? Bravo drives suffer corrosion around the water hose through the transom shield which restricts water flow causing your symptoms. Not heard of the issue with Yamaha but given the similarities of design its a possibility. With the work you've done you should have eliminated any issue with the engine so drive pickup would be suspect.
My way forward would be add a 1.5" through hull scoop pick up & either tee in to the through drive 6lp style or just block the drive pick up
Obviously if you already have through hull pick up I just wasted a little bit of my life typing this [emoji6]

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[wgc851]

As above, the Yammys suffer the same problem as the mercruiser on the transom sheild. Did you have a look at the transom sheild whilst the engine was out?

[osprey24]

I have plenty of water coming up, if I take my strainer cap off whilst the engine is running the water is bellowing out .
I have ordered a new flow sensor as mine has a small bit missing on the lift float. Not sure if it would cause the issue in having though.

Any other ideas?

[osprey24]

What was I looking for? I took engine and leg off and didn’t see anything untoward ?

I’m by no means a marine engineer

[beamishken]

Originally Posted by osprey24

What was I looking for? I took engine and leg off and didn’t see anything untoward ?

I’m by no means a marine engineer

If you unbolt the water hose connected where it bolts to the inside of the transom shield on a bravo you often find corrosion around the water hose which expands & restricts the water flow. The same can happen where the water hose fits to the tilt housing just ahead of the drive you can see it with the drive removed

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