Got diesel running...FINALLY

Benny17441 · Jul 21, 2015

The proof is in the pudding, is the engine overheating? Yes there is a right and wrong way to install the impeller. The impeller operates in a counterclockwise rotation viewed from the cover side of the pump. That means the leading edge of the vane at the base with the trailing edge following.

kloudie1 · Jul 21, 2015

No worry about the impeller, it will get itself straight within a half rev or so.. You may have a worn case or cover or cam in the pump.. The specification for the 1Gm, which is a very similar Yanmar, is for the pump to pass 1.3 gallons per minute at 2600 RPM engine sped.. The total case depth clearance should be around .008" (8 thousandths) . This is the difference between the impeller thickness and the depth of the pump case.. The cover should not have wear deeper than .008" in the grooves.. Sometimes that plate can be reversed to get an un-worn surface on the impeller side. If ya find by measuring with a micrometer that your clearances are too big, what is happening is that the water can go past the impeller vanes and back toward the suction side, decreasing the pump capacity. A gear headed buddy may be able to carefully surface grind the face of the case (where the cover seals) so that the clearance is back to 8 thousandths or so..

fawcettandrew · Jul 23, 2015

Hi,

I have an SB8 which is like a 1GM and I think has the same water pump. From my experiences on the SB8 - the water pump shouldn't need any positive pressure. It should easily lift water 12" to the engine and pressurize it enough to shoot out a crack in the hose (if you ever develop one). There's nothing small about that little pump.

From what you've said - I would replace it.

Also - I replaced my lift pump and now carry a spare. Seems like an easy thing to go wrong, only needs a little hole and it stops working just enough to starve your engine - nice!

Congrats on getting her running - there is redemption in a working diesel.
Andrew

Nelsonhow · Jul 23, 2015

I had a similar problem on my 2gm. The raw water pump stopped drawing. Good old boat magazine had an article about impellers where the rubber blades broke free of the brass hub Part in the center. It looked fine on visual inspection but slipped under load I replaced mine and at the same time replace the cover to the water pump and the gasket. The cover looked a little worn and was only about $15. This seemed to solve the drawing problem 100%. Takes about 15 minutes to change so it's an easy an quick attempt.
You might want to try it.

Benny17441 · Jul 23, 2015

kloudie1 said:
No worry about the impeller, it will get itself straight within a half rev or so..

Kloudie normally that would happen and to prove the point I once installed an impeller with different blades facing in both directions. Some time later I opened it up to check on it and all the blades except one had aligned themselves. That blade had taken a permanent alignment in the wrong direction so I had to replace the impeller. It could have been a fluke but since I have taken to insure I mount them properly and have not had a problem.

kloudie1 · Jul 23, 2015

Not saying it can't happen, but as the engine is shutting down, it will often roll backwards just a smidge and upset one or more blades. When ya open the cover, it looks like one has been set wrong but that typically is a last instant thing that happens at shutdown.

Maine Sail · Jul 24, 2015

braol said:
(Is there a right and wrong way to install the impeller? I notice that the "vanes" on the impeller all 'face' one way.....

You can try to install it with all the vanes going one way but it is simply unnecessary as one tap with the start motor and they self align. Course they will then back spin a bit and unalign when you stop the engine anyway...

People often over-think this and perhaps 50% of the impellers I pull out will have the vanes going in different directions due to the slight back spin that happens upon shut down..

Maine Sail · Jul 24, 2015

kloudie1 said:
Not saying it can't happen, but as the engine is shutting down, it will often roll backwards just a smidge and upset one or more blades. When ya open the cover, it looks like one has been set wrong but that typically is a last instant thing that happens at shutdown.

Bingo!! Having done literally hundreds of impeller replacements about 50% of them have reversed blades when you pull the cover off. Minute the engine is running they self align again...

Canyonkeeper · Jul 24, 2015

Same problem. I took the cover off of the pump (after closing the inlet). Turns out the impeller I had was spinning the hub. New impeller and was good as new.