No exhaust water stbd engine

[Chasemmc]

Fired up the 8v92ti's today. Both started, albiet with the crossover switch with little smoke. Port pumping out fine, starboard dry as a bone.

Replaced the impellors 6 months ago, have about 5 hours on them.

How would i go about diagnosing what is wrong?

Thx
Mark

[Pascal]

First thing i d check would be the impeller Just pull the cover and check it out without removing it unless you see missing blades

Could be the strainer but I find it to be rarely the case

And make sure the intake hose isn't loose. Rare but you never know.

[dottieshusband]

Fired up the 8v92ti's today. Both started, albiet with the crossover switch with little smoke. Port pumping out fine, starboard dry as a bone.

Replaced the impellors 6 months ago, have about 5 hours on them.

How would i go about diagnosing what is wrong?

Thx
Mark

Kinda a go look suggestion....check the intake screen and valve, take the back cover off the raw water pump and look at the back of the impeller....checking for blades and splines, could be the intake under the boat.

[Avenger]

Without being a smart@$$... Did you open the seacock?

[Chasemmc]

Never closed it.

Where is the strainer on the exchanger?

I so need a boat buddie. I'd ask Randy but but he'd make me beg. How humiliating would that be....😨

[yvella]

After a raw water rebuild i found the P.O had his guys replace impeller and they neglected to look for the missing pieces of impeller vanes I found alot of the pieces blocking the passage to discharge. Found same issue in the raw water pump on generator.

[racclarkson@gmail.com]

Since it ran dry, pull the impeller. I think you have to pull it to make sure the vaned all spring back. If it looks good, grease it. With the impeller out, take a hose and backfill the line from the pump down to the intake. Maybe it just needs a little encouragement to catch prime. If that doesn't get it I'll bet you have a bag or some such trapped in the screen.

[SEVEN]

Check the intake. Even though there may be water in it there may be an obstruction prior to the impeller. However I've seen impellers go out with hours of install. You say you didn't close the seacock, you should have taken on tons of water with it open. Was that the case? If not go to my first comment. Good luck

[Andy B]

The zincs can corrode make a mess and block the heat exchanger if left sitting for awhile, or if the cover plate is heavily worn the pump will have a hard time priming, and of course check to see if water is even getting in the boat strainer obstructed, thru hull etc.

[BOATER BOB]

Check the wear plate behind impeller cam and cover for wear on some pumps you can turn cover over and use.
Bob

[Walter P]

What Andy said happened to me last fall. My generator wouldn't take any "pink" and after checking everything out, I took the end caps off and discovered that the zinc's had corroded and since I didn't run the gen set for quite a while the heat exchanger was completely plugged.

Walt

[piripucha]

If the covering plate of the pump is hot you are not pumping water.You may have an air leak, either the hose is leaking or your wear plate make the impeller to vavitate. Beware of the new nitrille impeller the metal hub sometimes rotates free from the rubber part. The only way to notice this is to start the engine with the pump covering plate off, but this is a 2 man job. Good luck

[Chasemmc]

How long can the engine run without raw water and still be safe from heat damage?

[kelpy]

Not very long. If there is no water coming out the exhaust, shut it down.

[SEVEN]

No water and you will have heat damage big time. Real pricey to replace everything. Drop and anchor and ask for help.

[Chasemmc]

22262


I assume I have to shut the sea cock or get a bath before cracking the seal.
Also where is the filter grate so I can inspect for debris?

Are there baffles in the exhaust after the shower ring? Port side had a clam shell wash out of the end while I was watching. Wonder if a critter could be involved.

She is sitting in her slip, so not going to operate until issue resolved. It was just one of the suggestions was to turn over and feel cover plate for heat.

mark

[krush]

How long can the engine run without raw water and still be safe from heat damage?

Depends on what you are asking will get damaged. The engine can run at idle for at least several minutes (provided it is full coolant). The raw water pump cannot run very long at all starved of water...the impeller will melt from friction.

[SEVEN]

Are you sure it's oil on the cover? Shut the seacock off. There will be about a gallon of water spill into the bilge before it stops. Did you use a paper gasket when you changed it a few months ago? Or did you use a gasket sealer. That's what the black oil looks like to me however the photo is a little to blurry for my eyes. Pop the cover and pull that impeller and let us know what you find. Let's start there before going on.

[SEVEN]

The staining looks like a water leak from the cover. You also might want to switch out those screws on the cover plate to a hex head for easy on and off. Just don't crank the gasket down to tight.

[captddis]

The older pumps had brass shafts and they had a way of breaking.
Open the cover and see what it is .

[MikeP]

FWIW, if you started the engine with the seacock closed, it will ruin the impeller very quickly so that it will not pump water. BUT, when you pop the cover, the impeller will look perfectly OK. It only takes about a minute or two to do that.

IOW, if you forgot to open the seacock, started the engine, then walked back to observe water flow out the exhaust, saw none, walked back to shut off the engine, the impeller is probably shot by then but when you pull it out, it looks OK.

Yes, I've done this a couple of times. ;)

As far as damaging the engine, as K noted, the engine's cooling system is still functioning normally and it will take several minutes for temps to rise to harmful levels - there is a LOT of coolant in the system and it is being circulated by the water pump. I'd bet - though I've never actually tried it - that it would take at least 10 minutes at idle to get the temps anywhere dangerous.

I base that on the fact that it takes our 8V71's at least that long to reach 160F or thereabouts, the point at which the 160F thermostats open. IOW, there is virtually no interaction with the cooling water from the RW pump/heat exchanger until the thermostats open.

In any case, all you have to do is monitor the water temp gauges and shut down the engines before they get to, say, 180F to prevent any problem. Yes, I'm referring to monitoring the MECHANICAL gauges that you have installed in the engine rooms! :)

[Walter P]

I had the 1" dia SS shaft of one of my raw water pumps actually break in half. I wouldn't have believed it had I not seen it myself. We went through the same routine of trying to find a clogged intake, etc. It was when I removed the end cover and pulled the impeller that the problem showed itself. BTW things like that usually happen at the least opportune time. In my case I was at least 30 miles from a facility to tie up. I did a "Randy" and came in on one engine. Luckily I was able to acquire a replacement pump the next day from another boater that happened to have a spare that matched mine.

Walt

[jim rosenthal]

Doing a Randy.... you have just added an original phrase to the HOF lexicon.

[yvella]

I replied on earlier post about no flow but my bride reminded me once I had problemo and i had replaced impeller with an impeller that had i believe 8 blades and it didn't pump went and purchased another and it had more blades pumped fine. Dont know if anyone else has had this problem.

[SEVEN]

There are 8 and 12 blade impellers. I find the 12 moves much more water and the blades are more playable.

[Freeebird]

Dang, do I know when to come into a thread or what? Three "honorable" mentions, and I wasn't even participating.

As for making you beg, I'd never do that. Make you pay (for lunch) maybe, but not beg. You really do need to close those seacocks, especially during the winter months. As for your lack of water, I can't think of anything to add... unless there's something you forgot to tell us.

[Freeebird]

Oh, I do have one question. Why did you change those impellers?

As best I recall, you had that done (at great expense) last summer.

[Chasemmc]

I didn't change them after expensive diesel guy this pst summer. Turned the engines over and no water out of the stbd. Going up there this weekend to see if the spare impeller has 8 vs 12 vanes and the paper gasket.

Consensus seems to be yank impellor, install new, and see if it primes.
I guess once removed inspection will reveal if something broken inside like a shaft.

May need someone to pull my fat a$$ out of the engine room, if i get wedged in there 

[dottieshusband]

Checking the impeller is about the easiest thing to do. Leave one of the bolts loose, and pivot to end plate away on that bolt. Use bright light therapy to check the blades for presence. And be sure to check the splined hub and shaft for damage. I changed out an impeller last year in the middle of Mobile Bay. It looked fine at a glance, all blades in good shape...BUT the center hub splines were routed out! 1st time I'd seen that!

[bobk]

Checking the impeller is about the easiest thing to do. Leave one of the bolts loose, and pivot to end plate away on that bolt. Use bright light therapy to check the blades for presence. And be sure to check the splined hub and shaft for damage. I changed out an impeller last year in the middle of Mobile Bay. It looked fine at a glance, all blades in good shape...BUT the center hub splines were routed out! 1st time I'd seen that!

Did you mean rotted as opposed to routed? Rubber doesn't actually rot, but folks tend to refer to many kinds of deterioration as rot. I'm not trying to be picky on this, but knowing what is happening can be instructive. For example, I run my 6V92TAs 300 + hours per year. At about the 400 hour mark I have seen small cracks at the root of the vanes which is an early stage of failure. As a consequence I change impellers every year to be sure to avoid a failure underway. I never lost a vane that way. BTW, it is almost impossible to see the early cracks by simply looking at the blades while they are in the pump body. You have to take them out and flex them back and forth under a strong light. once the process starts, it seems to accelerate.

Bobk

[dottieshusband]

Did you mean rotted as opposed to routed? Rubber doesn't actually rot, but folks tend to refer to many kinds of deterioration as rot. I'm not trying to be picky on this, but knowing what is happening can be instructive. For example, I run my 6V92TAs 300 + hours per year. At about the 400 hour mark I have seen small cracks at the root of the vanes which is an early stage of failure. As a consequence I change impellers every year to be sure to avoid a failure underway. I never lost a vane that way. BTW, it is almost impossible to see the early cracks by simply looking at the blades while they are in the pump body. You have to take them out and flex them back and forth under a strong light. once the process starts, it seems to accelerate.

Bobk

Nope, I meant what I said. The center hub of the impeller is a splined soft metal, the drive shaft of the raw water pump is hard steel. The engine was a CAT 3412, and while all the blades of the impeller were just great, the drive shaft of the pump had spun the splines of the impeller hub...and it was smooth...so the pump drive shaft was spinning, but the impeller was sitting still....pumping no water.

[Freeebird]

I didn't change them after expensive diesel guy this pst summer. Turned the engines over and no water out of the stbd. Going up there this weekend to see if the spare impeller has 8 vs 12 vanes and the paper gasket.

Consensus seems to be yank impellor, install new, and see if it primes.
I guess once removed inspection will reveal if something broken inside like a shaft.

May need someone to pull my fat a$$ out of the engine room, if i get wedged in there Well, if you get stuck, call me. I'll see if I can find somebody to pull you out, or at least take pictures.

Guess I misread your post or didn't use enough fingers counting back the months to that impeller change.

[Chasemmc]

Closing the loop on this discussion, I replaced the impeller and lubed the fins extensively. Reaching in from the top of the engine this was realtively painless. The plate did show some signs of wear. The pulled impeller (just changed last summer, was in great shape so I'll keep it as an emergency backup in case I get stuck somewhere). I also carry two new impellers for prudence.

Fired up the engine and it re-primed. The flow was as good as the port engine.

I did have a bunch of crap come out of the exhaust, clam shells, wood, bits of sea weed, etc. Looks like it might have been home to a critter over the winter.

I have ordered two new end plates (they're cheap) and will swap them out when I next change the impeller.

Thanks for all the help. I don't think you old bucks know how helpful it is to have the reassurance of your experience and friendly advice. I am sure it can grow tiresome to answer the same stuff over and over and calm down the newbies.

Just a shout out, thanks again.
mark