Raw water pump - Ouch!

[jamhass]

Always good to pay close attention to leaky raw water pumps.

A friend had a very small drip on his RWP which he watched for a while and it then went away. Not long after the engine seized.

Turned out the (very) small weep hole had salted up and the leak (which continued) allowed raw water into the engine internals.

So, don't ignore even small leaks, and take a look at the design of your RWP, and if needed, enlarge the small weep hole.

Ours, fortunately, has a very large weep hole.

[Compass790]

Originally Posted by jimbunyard

Also, don't know what bearing was in the pump before, but a call to the bearing house to get the highest quality fully sealed bearing to replace the old one might help forestall this in the future. Same for the bearing in the drive end, though it might be better to have it sealed on the pump side only...if that's not available, you can always just pry the engine-side seal out.

Brilliant solution Jim!
I was thinking maybe fabricate a new cover with an shaft extension & an inward & outward facing oil seal if he had room.
Your way is much simpler & easier & if i ever get an engine with an integral salt water pump I will do your mod.
Reefmagnet you've hit the jackpot with this tip. Should be done at the factory.

[Bycrick]

There a bearings made of all different kinds of materials. While it’s true that with your water pump the bearings should be in oil all the time, you just proved that it isn’t always so. Try a really good bearing house for a more corrosion-resistant bearing. Not much difference in cost.

The most common lip seals are designed for oil and have a steel tensioning spring. Again, a good bearing house will have them rated for salt-water.

Having good seals means you can worry less about salt water getting where it shouldn’t.

[Reefmagnet]

I managed to get the shaft out of the pump last night in what can only be designed as a stupid design (bearings come out one end, the shaft the other). I'm now left with the remains of the two bearing shells and a spacer still firmly lodged with in the pump housing.

Looking at the overall design, I can see that the oil seal is susceptible to lack of lubrication in this application as the pump is high mounted, tilted upwards slightly (as is the engine) and the engine lubrication system for the PTO gear driving the pump can be described as a "splash" system at best. One of the bearings butts up right against the back of the oil seal, but I'm wondering if it's a feasible idea to use an open cage bearing for this bearing (as the original was) and a sealed bearing for the rear bearing and then use grease as a lubricant instead in front of the sealed bearing? This would remove the dependency for sufficient engine lubrication to reach the seal. Any thoughts?

[Compass790]

Originally Posted by Reefmagnet

I managed to get the shaft out of the pump last night in what can only be designed as a stupid design (bearings come out one end, the shaft the other). I'm now left with the remains of the two bearing shells and a spacer still firmly lodged with in the pump housing.

Looking at the overall design, I can see that the oil seal is susceptible to lack of lubrication in this application as the pump is high mounted, tilted upwards slightly (as is the engine) and the engine lubrication system for the PTO gear driving the pump can be described as a "splash" system at best. One of the bearings butts up right against the back of the oil seal, but I'm wondering if it's a feasible idea to use an open cage bearing for this bearing (as the original was) and a sealed bearing for the rear bearing and then use grease as a lubricant instead in front of the sealed bearing? This would remove the dependency for sufficient engine lubrication to reach the seal. Any thoughts?

that sounds ok but can you make an expanded cross section drawing of the parts layout of the existing setup to make it easier for the hive to picture it.
I, for one, have difficulty with written descriptions of layouts, a picture is worth a 100o words. You could just make a hand sketch & take a pic with your cellphone. Also a sketch of your mod. would be good
splash lubrication seems to work very well on our little Yanmar which is sloped upward too

[Reefmagnet]

Originally Posted by Compass790

that sounds ok but can you make an expanded cross section drawing of the parts layout of the existing setup to make it easier for the hive to picture it.
I, for one, have difficulty with written descriptions of layouts, a picture is worth a 100o words. You could just make a hand sketch & take a pic with your cellphone. Also a sketch of your mod. would be good
splash lubrication seems to work very well on our little Yanmar which is sloped upward too

Good idea! Here's the cross section of a similar pump with the same internal layout. It sits in front of another bearing that supports the PTO shaft. I'm thinking of replacing bearing 11 with a sealed one and packing grease in between it and the seal (10). It may even be possible to install a grease fitting between the bearings. I'll check the oil flow once the PTO gear is back in place and see how reliable it is, but I have my suspicions it's not that great!

[jimbunyard]

With the model we can make a more informed analysis.

Couldn't find anything on the Mini-33 V6, but the V4 looks the same, at least in the front end and water pump areas, so we'll go with that.

There should be plenty of splash oil lubrication there, even with the tilted-back installation. Before making any changes in the bearing/seal configurations, I would clean it all up and try and verify that there is sufficient lube at the accessory drive. It may be counterintuitive, but you might try running the oil level a little higher to aid in this.

According to manual, the accessory drive bearing is a 6205C3, which is a common open (unsealed or shielded) bearing. Can't tell from your first picture, but if someone has replaced the open outer bearing with a sealed or shielded one, certainly a lack of lubrication for the pump bearings would result.

If it turns out that there is indeed insufficient oiling at the accessory drive, fully sealed/permanently lubricated bearings could be an alternative solution, but as you are aware, lubrication for the lip seals on the shaft then becomes an issue, but again, if there is no oil there, there's no need for a seal; the bearing seals would (probably) be enough.

Also if there is insufficient splash oil at the accessory drive front brg, there's likely insufficient at the back, again fully sealed, permanently lubricated bearings could by used there as well. A comparison could be made between the service an alternator bearing (side load, high temperature) and the acc. drive or water pump bearing (axial load, moderate temperature) as to the potential suitability for this application.

Also, don't forget the item 8, 15x2 oring shown in your part drawing. It is important as, in the event of a leaky seawater seal, it acts as a slinger, or deflector, to keep water from running down the shaft and getting sucked into the engine.

And make sure that there is not excessive backpressure in the raw water system (clogged HE, exhaust elbow, etc.) as a sea water pump in good shape can generate a lot of pressure, which will find its way through the path of least resistance

[skenn_ie]

Originally Posted by Reefmagnet

That belt driven pump idea sure sounds good. It's got to be much better than relying on a two dollar seal to keep the ocean out of the engine! And I've thought of keel cooling / dry exhaust but that would turn most sailboats into ovens, especially mine


..

$2 seal ? Doesn't it have a ceramic/graphite pressure seal ? The gear-driven ones that I have seen have a pressure seal, then an air gap to bleed any water leakage, then an oil seal to keep the oil in the engine. There is no possibility of water getting into the oil.

[Blacknblue]

Originally Posted by Compass790

I feel your pain as deferred engine work has cost me a lot as well but even worse was I got advice from a well regarded diesel " mechanic" that lead me astray.

I’m guilty too.
There was a knock at idle to which that I must do something about. I put it off when I found a full top end overhaul was about $5000

3 months later a valve dropped and destroyed the engine. The exhaust mixer had been leaking salt water back onto the rear valve. The valve deteriorating was the knock I could hear at idle- nothing else was abnormal.

$100,000 for 2 new engines installed😳 ( yes, $100k!)

[Reefmagnet]

Originally Posted by skenn_ie

$2 seal ? Doesn't it have a ceramic/graphite pressure seal ? The gear-driven ones that I have seen have a pressure seal, then an air gap to bleed any water leakage, then an oil seal to keep the oil in the engine. There is no possibility of water getting into the oil.

It does, but if that leaks it relies on the $2 seal to keep the water out of the engine.

[Reefmagnet]

Originally Posted by jimbunyard

With the model we can make a more informed analysis.

Couldn't find anything on the Mini-33 V6, but the V4 looks the same, at least in the front end and water pump areas, so we'll go with that.

There should be plenty of splash oil lubrication there, even with the tilted-back installation. Before making any changes in the bearing/seal configurations, I would clean it all up and try and verify that there is sufficient lube at the accessory drive. It may be counterintuitive, but you might try running the oil level a little higher to aid in this.

According to manual, the accessory drive bearing is a 6205C3, which is a common open (unsealed or shielded) bearing. Can't tell from your first picture, but if someone has replaced the open outer bearing with a sealed or shielded one, certainly a lack of lubrication for the pump bearings would result.

If it turns out that there is indeed insufficient oiling at the accessory drive, fully sealed/permanently lubricated bearings could be an alternative solution, but as you are aware, lubrication for the lip seals on the shaft then becomes an issue, but again, if there is no oil there, there's no need for a seal; the bearing seals would (probably) be enough.

Also if there is insufficient splash oil at the accessory drive front brg, there's likely insufficient at the back, again fully sealed, permanently lubricated bearings could by used there as well. A comparison could be made between the service an alternator bearing (side load, high temperature) and the acc. drive or water pump bearing (axial load, moderate temperature) as to the potential suitability for this application.

Also, don't forget the item 8, 15x2 oring shown in your part drawing. It is important as, in the event of a leaky seawater seal, it acts as a slinger, or deflector, to keep water from running down the shaft and getting sucked into the engine.

And make sure that there is not excessive backpressure in the raw water system (clogged HE, exhaust elbow, etc.) as a sea water pump in good shape can generate a lot of pressure, which will find its way through the path of least resistance

I think the issue is the pto gear bearing is caged and it restricts splashing directly onto the pump bearings. The different in condition between this bearing and the pump bearings seems to verify this. The water and oil emusified at the pump facing side of the pto bearing forming an additional barrier at the first occasion of water contacting the bearing. The inside of the pump itself had absolutely no evidence of emulsion when disassembled.

This pump failed with little hours and it may just have been faulty from the outset. So the problem may have prevented the oil getting to where it needed to be.

[skenn_ie]

Ceramic bearings anyone ? Bearings in belt-driven pumps are likely to be sealed, why not the same bearings in gear-driven pumps ? I have been considering installing mine as gear driven, but that does set the speed a bit high for comfort AND turn pump failure immediately into engine failure and major overhaui to remove broken teeth. Belt driven would be slightly less catastrophic. Either way, bearing are not something to scrimp on. Get the best you can find. These may not even be the pump manufacturers ones.

[Wotname]

Originally Posted by skenn_ie

......I have been considering installing mine as gear driven, but that does set the speed a bit high for comfort AND turn pump failure immediately into engine failure and major overhaui to remove broken teeth. Belt driven would be slightly less catastrophic. .........

I can't speak for your engine (don't know what it is) but many direct driven raw water pumps are simply tang driven off the end of the camshaft i.e. runs at half the crank rpm.

However it seems to me that many of you are overthinking the problem. The OP identified the root cause in the first post. Lack of timely maintenance!

A slowly developing leak in the raw water pump gives plenty of warning - that is what the slinger and weep hole is for. The design of these water pumps is quite satisfactory. Attend to to initial problem and the rest won't cascade into a serious problem.

Thanks to Reefmagnet for highlighting the real problem - it is a timely reminder for the rest of us. :Thank:

Jamhass hit the nail on the head back in post #16

Originally Posted by jamhass

Always good to pay close attention to leaky raw water pumps.

A friend had a very small drip on his RWP which he watched for a while and it then went away. Not long after the engine seized.

Turned out the (very) small weep hole had salted up and the leak (which continued) allowed raw water into the engine internals.

So, don't ignore even small leaks, and take a look at the design of your RWP, and if needed, enlarge the small weep hole.

Ours, fortunately, has a very large weep hole.

[lituya1617]

I beg to differ. I was a commercial fisherman with a wooden boat for many years. The nonsense about raw water cooled heat exchanger and water-cooled exhausts is just that, nonsense. If you have a "yachty" mentality, you may buy the nonsense but no commercial fisherman wants to risk his life and income to the possibility of a weed-choked water intake, a broken v-belt, a spun keyway, a broken or burned impeller made of rubber, a salted exhaust water injector, a ruptured hose that will sink you quickly, or a leaking/plugged heat exchanger. Pumping a continuous large volume of salt water into a boat is dumb! Many pleasure yachts have sunk because of this application. Hoses break, boats sink. Not good. A keel cooler heat exchanger is a no-moving-parts simple system fastened to the hull in the protected garboard-keel angle. It has minimal drag, less than the propeller shaft and strut, and contains antifreeze and water with anti-rust compounds to protect the engine. The engine water pump is the only pump used - and it is used with internal heat exchangers too. Such pumps are highly reliable and easily repaired. You are required to have a water-cooled exhaust on a boat with an enclosed engine room; therefore, your engine has an exhaust header that is water cooled. However, from the header to the outside air, the exhaust pipe is simply insulated with fiberglass and placed inside a metal heat shield to prevent skin burns. An efficient and cheap automotive muffler can make the exhaust nearly inaudible. The heat shield also functions as a passive cooling vent for the engine room. Having the exhaust go straight up allows one to hear the function of the engine and look for signs of problems like smoke or weird noises - things a water lift muffler prevent. But the worst thing about the water-cooled and water injected exhaust systems so common on sailboats and yachts is the fact that the exhaust valves and cylinders are exposed to salt water vapors when the engine is not running. Think about this: your open steel exhaust valves and the iron heads and steel rings in the cylinders directly communicate with a large volume of warm salt water when you shut down the engine. When the engine cools, the air in the exhaust shrinks and draws the water even closer to the block. Over time, a matter of only a few months, you can rust up you engine to the point it needs a complete overhaul - just because you "like" a water-cooled exhaust. Not a wise choice. Sure, you can flush the system with fresh water but even that is not good for the internal parts of your engine. My opinion: keel coolers are by far the best option.

[jimbunyard]

Originally Posted by skenn_ie

$2 seal ? Doesn't it have a ceramic/graphite pressure seal ? The gear-driven ones that I have seen have a pressure seal, then an air gap to bleed any water leakage, then an oil seal to keep the oil in the engine. There is no possibility of water getting into the oil.

Some might say I live a sheltered life, but I've never seen a flexible rubber impeller raw water pump with a ceramic/graphite pressure seal, though such seals are the norm for freshwater/engine coolant circulation pumps as well as other centrifugal pumps like water or well or pool pumps.

As for "there is no possibility of water getting into the oil", standard rubber lip seals generally only work one way; they can and sometimes do allow contaminants, for a variety of sometimes subtle dynamic reasons, to enter a system into which they are 'sealing' another substance.