Yanmar 2QM15 Maintenance

2QM15 Impeller Question

Ok... I have the service manual and the pictorial diagrams. But no where in the manual do I see a reference definitively pointing to where the impeller is, how to change it, or even mentioning it at all... ??? So I'm hoping someone that has (or has had) a 2QM15 can tell me if I'm about to do this the right way, along with any pitfalls I may run into.

I'm ASSUMING, that the impeller is inside the plate that's ATTACHED to and BEHIND the water pump (looking at the engine from the front.

I'm ASSUMING that I need to close the seacock for the water intake and exhaust (it's raw water cooled).

I'm ASSUMING that I need to loosen the water pump drive belt, remove what looks like 2 bolts holding the water pump in place, then twist the pump without disconnecting the hoses to get to the impeller plate on the back of the pump.

I'm ASSUMING that I can then open the plate, clean it off, remove the old impeller, insert the new one, put on the new gasket, close it up, reinstall the water pump, reopen the intake and exhaust seacocks, start the engine, and inspect for any leaks.

If any of these assumptions are incorrect, please let me know. But here's the part that I'm not sure about... The guy at the marine store who supposedly knows this engine didn't give me a gasket that I assume will need to be replaced for the water pump itself. So does that mean:

1. The impeller can be removed without removing the water pump?
2. OR I need to go back and get a water pump gasket before I start this?
3. OR the water pump is just mounted to the motor with the two afore mentioned bolts and doesn't actually have or need a gasket?

You're on the right track. I had a 2GM20 for years and did about everything that a layman could be expected to do.

You've got the manual. That's good.

And you've figured out that you need to stem the flow of water by shutting the thru-hull valve. You'll do fine.

And yeah, that impeller is behind all the stuff you mentioned. You have to take the water pump off - or at least I had to - in order to change the impeller.

But I don't think anyone spilled oil on your intake filter. That oil is actually old diesel fuel. Diesels aren't much like gas engines and when they start there can be a lot of fuel being puffed around because they don't have an intake butterfly valve. It's just open from the cylinder to the filter for a moment. I think it just sorta backfired and puffed oil out the intake.

Have Fun! You're doing fine.

I have a 2QM15 on my 1980 sailboat. The raw water pump mounts to the engine block with the 2 bolts. If you undue the nuts, the pump rotates slightly to release the belt tention and you can slip the belt off the pully. The pump needs to come off the engine so you can get to the back plate and gain access to the empeller. Yanmar sells a "rebuild" kit with all the gaskets, empeller etc you need. You will need to close the raw water seacock before undoing the hose clamps, and have a small bucket / container ready to catch a little water that drains back out from the engine. After that, remove the cover plate and replace the empeller per the service manual. Make sure you install the empeller the correct way since the blades will have to be bent slightly to get it to fit, and if you put it in backwards, you risk breaking one or more off when you restart the engine. It is also recommended to lubricate the empeller also when putting it in to help it go in better, and to prevent running it "dry" until water gets sucked back in later.

Once you have it replaced reverse the process to remount it, and adjust belt tension by rotating the pump to the right belt tension before locking the nuts all the way down.

I was told once by a engine mechanic to keep a spare pump on hand ready to go if the empeller ever broke underway. It is easier and quicker to replace the pump with a spare than replace the empeller underway in heavy seas. His thinking was that the empeller would probably break at the worst time, and in 5 ~ 8 minutes you could replace the entire pump verse 20 ~ 30 minutes to do the entire empeller change out. Something to consider.