Yanmar Raw Water Pump

[warmbluewater]

I have a Yanmar 4LH-TE in my sailboat. A couple of months ago my exhaust started to steam with the water discharge. Research says partially clogged heat exchanger or impeller issue. Essentially, not enough flow through exchanger causing higher temps. Decided to look at impeller first. It is toast so I will replace it. What I do not understand is inside the pump housing it appears there is a build up of scale. See pic. The part I do not understand is the scale is so perfect, yet not symmetrical. See the different thickness in the tan/yellow layer. Is is actually part of the pump housing to create the offset for the impeller? Or do I have a real problem here? Beyond just a new impeller?

[Wotname]

Waiting for photo...
However there is a raised section in the pump body on the perimeter to compress impeller blades as they rotate.

[warmbluewater]

Sorry my weak wifi would not let me upload a photo. Working on that. Sounds like what looks a bit like scale build up is part of the pump. Whew! Much cheaper than a new pump.


Sent from my iPhone using Cruisers Sailing Forum

[warmbluewater]

Sent from my iPhone using Cruisers Sailing Forum

[westsail42]

Originally Posted by warmbluewater

I have a Yanmar 4LH-TE in my sailboat. A couple of months ago my exhaust started to steam with the water discharge. Research says partially clogged heat exchanger or impeller issue. Essentially, not enough flow through exchanger causing higher temps. Decided to look at impeller first. It is toast so I will replace it. What I do not understand is inside the pump housing it appears there is a build up of scale. See pic. The part I do not understand is the scale is so perfect, yet not symmetrical. See the different thickness in the tan/yellow layer. Is is actually part of the pump housing to create the offset for the impeller? Or do I have a real problem here? Beyond just a new impeller?

If your are talking about the shallow "bump" on this inside of the housing, that is by design. The impeller vanes pass up and over the "bump" that is how it sucks water in from the intake side.

[westsail42]

incidentally, I had a situation where a vane has broken off (like yours are about to), laid up against the inside the housing, and occasionally was spun around the inside. Sometimes it would get stuck over the intake port, nearly blocking it completely, then free it self and get stuck somewhere else.

Result: intermittent overheating. Caused a real head scratcher. Sometimes there would be water in the exhaust, sometimes not. From this experience, I install new impellers every 100 hours.

[jackj17]

Hi
I rebuilt mine this winter because I was unsure of it condition I believe the bump is built in but from the picture the scale might be over doing gasket cement If there is only one spare to have it will be an impeller Way cheaper than a motor
JJ

[Jetx]

Originally Posted by westsail42

If your are talking about the shallow "bump" on this inside of the housing, that is by design. The impeller vanes pass up and over the "bump" that is how it sucks water in from the intake side.

Yep, like Westsail42 says, that's how it's supposed to look. Once you get the impeller out, you'll see that there are two holes in the outer wall of the pump -- one on one side of that bump and one on the other side of the bump. Those are the pump inlet and pump discharge openings.

Here's a clearer photo in an online tutorial posted by Maine Sail...
Rebuilding A Raw Water Pump Photo Gallery by Compass Marine How To at pbase.com..