Raw water problem - raw knuckle problem

[Seattle Scott]

So why does the Yanmar 4 series have the raw water impeller housed in the back/aft end of the pump? I always assumed it was on the front. Anyway, my exhaust was running dry so I checked the sea strainer first (clear) and then opened the thru hull with the strainer top off and water flooded in. So then I make a big assumption and jump to the raw water pump impeller. I don't have side access to the front 1/3 of the engine. Good front and top access and back accesse though. So I have to take the alternator off to reach the back of the pump. Then I have to work blind ( the cover if facing away from me) get the cover off, check the impeller in place with a mirror, it look OK but the boat is 20 years old so I start to take impeller out. this takes about 1/2 hour picking at it. Get it out and it is just perfect. Put a new impeller in ( this takes about 45 minutes getting the blades into the housing) and put everything back together and rebolt the alternator. That was a 2-3 hour bloddy knuckle mess. Start engine - no water. So I disconnect the hose out the back of the heat exchanger and water pumps out great. Then I just work my way down stream taking each connection apart and getting good flow until the final fitting into the exhaust elbow. OK its the elbow. I got that off at the manifold and at the muffler, I couldn't get the exhaust hose off of the elbow. Like a warrior with his sword I left the dock with my elbow and 3 feet of exhaust hose held high.Anyway, the last thing I will check if no water or an overheat problem in the future is going to be the raw water pump impeller. Well at least I know where it is, though I have never really seen it. On the elbow issue, based on what other have said I know I will not be able to break loose the elbow from the manifold flange thingy. So I was just going to drop it off at the local Yanmar parts and service place and get them to do the heavy lifting and also get a new elbow. Anyone have a better idea?Finally, I got the boat with about 1300 engine hours, I put on 400 hours and then sudden complete blockage this weekend while at the dock.

 

[Seattle Scott]

So why does the Yanmar 4 series have the raw water impeller housed in the back/aft end of the pump? I always assumed it was on the front. Anyway, my exhaust was running dry so I checked the sea strainer first (clear) and then opened the thru hull with the strainer top off and water flooded in. So then I make a big assumption and jump to the raw water pump impeller. I don't have side access to the front 1/3 of the engine. Good front and top access and back accesse though. So I have to take the alternator off to reach the back of the pump. Then I have to work blind ( the cover if facing away from me) get the cover off, check the impeller in place with a mirror, it look OK but the boat is 20 years old so I start to take impeller out. this takes about 1/2 hour picking at it. Get it out and it is just perfect. Put a new impeller in ( this takes about 45 minutes getting the blades into the housing) and put everything back together and rebolt the alternator. That was a 2-3 hour bloddy knuckle mess. Start engine - no water. So I disconnect the hose out the back of the heat exchanger and water pumps out great. Then I just work my way down stream taking each connection apart and getting good flow until the final fitting into the exhaust elbow. OK its the elbow. I got that off at the manifold and at the muffler, I couldn't get the exhaust hose off of the elbow. Like a warrior with his sword I left the dock with my elbow and 3 feet of exhaust hose held high.Anyway, the last thing I will check if no water or an overheat problem in the future is going to be the raw water pump impeller. Well at least I know where it is, though I have never really seen it. On the elbow issue, based on what other have said I know I will not be able to break loose the elbow from the manifold flange thingy. So I was just going to drop it off at the local Yanmar parts and service place and get them to do the heavy lifting and also get a new elbow. Anyone have a better idea?Finally, I got the boat with about 1300 engine hours, I put on 400 hours and then sudden complete blockage this weekend while at the dock.

 

[Paul Akers]

Remove the pump

I don't know what model engine you have, or the boat size. But you may be able to remove the pump to work on it. The 1,2,3 cyl Yanmars may allow you to do so. When I change mine (1988 3hm35f), I usually remove it to work on it. I usually do this annually. Takes about 30 minutes to do once you have it off.Your other problem with the elbow sounds quite accurate for the # hours the engine has. Parts will be frozen, as you found. Let Yanmar do it or your yard (they have experience, too) and save your knuckles. Get a new elbow because you will never get the old one clean.

 

[Paul Akers]

Remove the pump

I don't know what model engine you have, or the boat size. But you may be able to remove the pump to work on it. The 1,2,3 cyl Yanmars may allow you to do so. When I change mine (1988 3hm35f), I usually remove it to work on it. I usually do this annually. Takes about 30 minutes to do once you have it off.Your other problem with the elbow sounds quite accurate for the # hours the engine has. Parts will be frozen, as you found. Let Yanmar do it or your yard (they have experience, too) and save your knuckles. Get a new elbow because you will never get the old one clean.

 

[Steve Dion]

I think that those engines are gear driven?

Scott:I think that those engine that you are referring to have gear driven pumps (no belt), is that correct?If you need to work blind and CANNOT remove the pump, maybe you should look into a SpeedSeal. They allow you to remove the impeller cover with a few knurled thumb nuts. You would remove the top two and just loosen the bottom two. The SpeedSeal costs about $57 and makes impeller change out much easier.

 

[Paul Akers]

Gear Driven?

Sorry guys. If it is belt-driven then it would be easier to remove to work on.

 

[Franklin]

Access Panel

If your boat is like mine, cut an access panel into the side that is blocking it and put a hatch there. I did it this past spring to replace my impeller and it worked great. I'm very glad I did because it comes in great use now. I had to take the whole exhaust off to replace a freeze plug. If your interested in this, do a search in the archives (if it's fixed) for engine access panel. This is commong for the 376.

 

[Seattle Scott]

Yep gear driven

I'm thinking Franklin has the right idea. Even with the Speedseal cover, it would take forever to remove and replace the impeller and in the present access I can't inspect the impeller in place. Without side access I am still going to have to remove the alternator to get to the impeller cover.