In arms way

[velella15]

After coming off the slip the impeller in the sea water pump on my Yanmar 3YM 30 threw 2 of its arms. The arms could not found in the pump and are presumably lodged in the heat exchanger somewhere. After replacing the impeller, less than the normal amount of water appeared to be pumping through the engine. Any experience around on how and where to find the missing arms?

[s/v Jedi]

Remove the hose on the output side of the pump and hope the pieces are right there. If not, the heat exchanger core must be cleaned.

[MarkJ]

Look at the enterence to the oil cooler.

That's where the previous owners seemed to store all theirs!

Mine is a Yanmar 4JH3e

Mark

[Frankly]

Not sure about the YM heat exchanger, but on the GM series the water pump parts usually stop at the input of the heat exchanger. This is a 3 pass heat exchanger so a little blockage can have big impact on flow. Might try first remove the hose on the front of the exchanger cap and look in with a light. If no luck removing the exchanger cap is NBD.

[Cheechako]

Yes look at the entrance to any heat exchangers and oil coolers. Found a bunch in my Perkins transmission cooler once. Fortunately they often jam at the inlet end.

[velella15]

Thanks MarkJ. More engine room work! Every yachtie knows "engine room" is an oxymoron - there's almost no room!

[RDW]

Before tearing into a lot of work look upstream, i.e. before the water pump. I worked extensively to find parts of impeller only to find it in the intake to the impeller housing.
Just a quick look might save time.
RDW