Risers and seawater impeller, 350 MAG MPI

[Toddavid]

Previous owners used the boat exclusively in salt water, 83 hrs logged. To be safe, I pulled a riser to get a state-of-the-union assessment. To my surprise, and possibly untrained eye, the side I pulled looks almost new. Yes?





Any reason to pull the other side when this one looks so clean?


My impeller housing, on the other hand, does not look so fresh. Correct me if I am wrong, but scoring like this means a housing change, right?






Thanks in advance.

 

[Don S]

Re: Risers and seawater impeller, 350 MAG MPI

That pump is looking really tired and worn. Part of the material the impeller seals against is gone.

Manifolds look fine, they are the dry-joint style and much better in salt water. What you need to watch for on those is restricted passages in the elbow where the water exits into the Y pipe. That is where those get plugged up first, and you see the most corrosion.

PS: Just for reference, add your engine and drive serial numbers to your signature. Makes it a lot easier for others to get accurate info without asking. Parts lists and manuals go by serial numbers, not year, and Merc only list lists engine as "1998 and newer" after 97.

 

[Toddavid]

Re: Risers and seawater impeller, 350 MAG MPI

Thanks, Don.

Engine serial: 0W635474

What would cause such premature wear on the housing? I run on muffs in the driveway, but only at idle.

Impeller itself was intact, but with a little pitting on the lobe edges.

 

[MarkSee]

Re: Risers and seawater impeller, 350 MAG MPI

....and possibly untrained eye, the side I pulled looks almost new. Yes?
Any reason to pull the other side when this one looks so clean?

Seems like your eyes are looking pretty good there.

To me since you're going to need to put new gaskets on the side you pulled and to check where Don indicated, it seems like you'd want to pull the other side so both were checked and got new gaskets at the same time.

Mark

 

[Toddavid]

Re: Risers and seawater impeller, 350 MAG MPI

Oh, when you refer to the y-pipe passages, are you referring to the passages on the bow side of the risers that the water hoses attach to? Other then peering inside with a flashlight, what else can be done to inspect? Run a stiff wire through them?

 

[Don S]

Re: Risers and seawater impeller, 350 MAG MPI

The arrow in the picture shows where they plug up first.



As far as the other side. If the side you have apart looks ok, I wouldn't pull the other side apart unless it's getting hot. Those gaskets are around $35 each as I recall. And DO NOT over-torque those gaskets. It destroys them.

What would cause such premature wear on the housing?

Never flushing it. The salt builds up, dries out and turns gritty.

 

[Toddavid]

Re: Risers and seawater impeller, 350 MAG MPI

Thanks, Don, I see that passage now. Best way to check them? Stiff wire? Peering in does not show blockage.

Is cleaning the gasket surface with scotchbrite pad best was to prep? I already scraped as much residue off as possible.


Funny, I figured they must have been doing regular flushes when I saw the clean manifold and riser passages, but the water pump condition would suggest otherwise... I'll take a pump replacement over manifold replacements, though. Wrenching on boat engines is crazy compared to the cars I am used to. I have to get comfortable wrenching on my stomach, mostly by feel!

 

[Don S]

Re: Risers and seawater impeller, 350 MAG MPI

I see that passage now. Best way to check them? Stiff wire? Peering in does not show blockage.

If it looks good, it's fine. They would be all corroded rusty and blocked off it they were a problem.
Put it back together and find something else to worry about.

 

[Toddavid]

Re: Risers and seawater impeller, 350 MAG MPI

Already doing that. Just started a thread in the hull forum about water in my transom. :blue:

 

[Don S]

Re: Risers and seawater impeller, 350 MAG MPI

Already doing that. Just started a thread in the hull forum about water in my transom. :blue:

That's not good..............

 

[Toddavid]

Re: Risers and seawater impeller, 350 MAG MPI

Yeah, hence the frowny face. Maybe I should add some tears and hari-kari emoticons?

 

[MarkSee]

Re: Risers and seawater impeller, 350 MAG MPI

Yeah, hence the frowny face. Maybe I should add some tears and hari-kari emoticons?

...that might help but certainly don't put the riser back and get it all hooked back up just in case something really bad is going on and you need to pull the engine....

Mark