Yanmar 3YM30 Seawater Pump

[anniebray]

My 2008 Sadler 290 was originally fitted with the above ref engine and from the start, priming of the seawater pump was never very positive. Suction pressure was feeble even though my Vetus water filter is below waterline. I have just obtained & fitted a third pump which is a vast improvement . As a trial I removed the feed hose from the pump inlet, attached a spare piece of 19mm bore hose & successfully removed bilge water. I could even feel a strong suction pull when the end of the hose was placed directly against the hull. The original pump is Yanmar Ref 128990-42500 & has 17mm dia inlet & outlet (price £450 inc vat), the later pump which I have just fitted is Yanmar Ref 128990-42510 has 19.5mm inlet & 17mm outlet (price £300 !!) . The outer dimensions of both pumps are identical except for inlet nozzle so either pump will fit with the same M 19 (Yanmar ref 104511-78780) drive belt. It would appear that Yanmar have at last re-engineered this pump.

 

[RichardS]

I have the 128990-42500 pump on both my 3YMs and I've not noticed any problems with suction provided that the system upstream of the pump is well-greased and air-tight.

Apart from the nozzle sizes has the design been changed in any other apparent way?

Richard

 

[anniebray]

I have the 128990-42500 pump on both my 3YMs and I've not noticed any problems with suction provided that the system upstream of the pump is well-greased and air-tight.

Apart from the nozzle sizes has the design been changed in any other apparent way?

Richard

I have not taken the new pump apart so I am not aware of any other changes other than nozzle sizes . I remind you this is the third Yanmar pump I have fitted & the improved performance is very clear to me. When the boat was new & I was getting problems with priming I noticed that the piping upstream of the pump was PVC & kinked where it was bent. I got my local Yanmar agent to check this out (Rampart the builders went bankrupt 2 weeks after boat delivery) & they replaced the PVC with correct thick walled rubber tubing but otherwise found nothing wrong. Most of my engine servicing has been carried out by a specialist marine engineer who is a member of my club & has a sound reputation but nevertheless I have always been aware that priming was weak. My boat is a twin keeler & propulsion is by saildrive & quite often I navigate in shallow waters where the water intake is likely to be muddy thus accelerating pump wear. Also I was concerned that Barnacle growth inside the leg might restrict intake so I had an extra intake fitted in the hull plumbed so that I could use both intakes or just one. If you search thro the YBW archives you will find that problems with Yanmar pumps is not uncommon. My previous boat was fitted with a Beta 28 & the performance of the seawater pump was far superior to my experience with Yanmar ie until I fitted this latest Yanmar pump. BTW I'm fairly certain my new pump was manufactured by Johnson.

 

[Halo]

I have a spare pump for my 3YM30. There is no doubt the original pumps were weak primers and are still prone to fail when the shaft seal leaks. It is important not to tighten the drive belt and if you fit a new impeller then lubricate it with plenty of glycerin (available cheap from chemist) and prime as much as you can by filling the strainer before closing it tightly (you may need to juggle with the seacock.