Sureseal shaft seal.

[ianc1200]

Could anybody help me understand these.

I have an Aquastar 38, with twin 250hp BTA Cummins, Hurth gearboxes, and Sureseal shaft seals. The boat is on the hard, & I want to run Rydlyme in a closed circuit through the oil cooler & heat exchanger. The reason has been the SB engine runs about 10C hotter than the port engine. There seems to be less water coming out of it's exhaust. Yesterday set the system up, and promptly starting losing the Rydlyme/water mixture. I realised it was coming out of the prop bearing, and a closer look showed there is a take off on the pipe from the raw water pump to the oil cooler. This take off feeds the Sureseal, then there's a take off from that to the port engines shaft seal, and finally a take off to the corresponding pipe between raw water pump and the oil cooler for the port engine.

My main query is - should this feed leak out of the prop shaft? I'm thinking probalbly the answer is no, and this is why I'm seeing a lesser amount of water coming out the SB exhaust & a higher temperature for that engine.

Secondly, I can't understand why effectively, both engines cool both props.

The photo shows the SB shaft, with the feed from the SB raw water pump removed, but the cross feed (braided pipe) left on.

 

[BB1]

My main query is - should this feed leak out of the prop shaft? YES it should.
Secondly, I can't understand why effectively, both engines cool both props. It's to lubricate/cool the shaft bearing behind the seal.

As for water flow, could be a blockage in the raw water system, heat exchanger, intercoolers, oil coolers, exhaust elbow??

 

[TK Blue MAX]

Secondly, I can't understand why effectively, both engines cool both props. It's to lubricate/cool the shaft bearing behind the seal.

Its feeding to both so if you have to run on one engine, the other prop will freewheel , so it needs cooling or it will wreck the seal.
Or you can lock the non running shaft mechanically

 

[ianc1200]

My main query is - should this feed leak out of the prop shaft? YES it should.
Secondly, I can't understand why effectively, both engines cool both props. It's to lubricate/cool the shaft bearing behind the seal.

As for water flow, could be a blockage in the raw water system, heat exchanger, intercoolers, oil coolers, exhaust elbow??

Re water flow, this version doesn't have raw water cooled aftercoolers as the larger versions. In the raw water system there is simply seacock/strainer/pump/oil cooler/heat exchanger/exhausts. As from yesterday, I now know to add the Sureseal.

Re water coming out of the prop bearings, that's a pity, I thought I had found the answer.

It is less than the port engine - perhaps 10% less - and it takes a long time to come through compared to the port engine. When it eventually comes out it's like a big bucket has been chucked out. Regardless of the engine temperature the water coming out the back isn't even tepid, it's cold. I have also used a temperature camera to compare both at same revs, and there's no real difference. The temperature sensor and gauge will be changed, but I had hoped I'd found the reason for the difference. Next week I'll run the Rydlyme through the port engine next week and now expect to see the same thing (I'll do water only first, and once leak seen plug the feed to the seal).

As a lot of us will fill the raw water system with anti freeze for the winter I wonder how many have a similar set up & not realise (like me until today) it will simply leak out of the bearing leaving the HE and oil cooler empty.

 

[Mr Googler]

Which engine is the calorifier on

 

[ianc1200]

SB - the one in question.

 

[Bandit]

I have had Tides Marine Sureseals for 20 years in my Aquastar 48, they are as dry as a bone.

My engine room is dusty not wet.

The photo is a bit dinghy but it looks like you have a spare seal just ahead of the one in use mounted ahead of the one in use.

You can slide the spare seal down in an emergency in the water, I would only do that in an emergency. Far better to do that with the boat ashore or to dry it out on a tide.

As mentioned above the crossover is in case one supply line is blocked or one engine is shut down.

You should prove your supply lines each year by running into a marked bucket and get about 4.5 litres a minute on each one.

The hose tail has a very small ID and is easily blocked by crud or a flake of rust.

The supply lines do fur up. When the boat is ashore I would dismantle the whole system back to the engine or gearbox examine/clean all the hose tails and fit new hose. The shaft seals should be replaced every 5 to 7 years and to replace spare seals you will need to uncouple from the Coupling and either pull back or draw the shaft. Check cutless bearings and replace if required.

Talk to the guys at Tides Marine in Poole they are very helpful.

 

[ianc1200]

Thanks for the thoughts. If they are meant to leak through then all would appear to be working correctly, but the hoses could do with replacement, and it's good to understand now why there is the crossover - and I had been running on one engine quite a bit of time to get speed down.

 

[Mr Googler]

SB - the one in question.

So they will generally run a bit cooler as the calorifier takes some of the heat away. Rydlyme flush never a bad thing though. What temps are you running at? Impellers been checked / replaced?

 

[NBs]

Hi, i think no chemical, pleace.

This way is beter.

Cummins Marine Aftercooler Maintenance

 

[Tranona]

This shaft-seals.co.uk/wp-content/uploads/2017/02/SureSeal_Maintenace_Schedule.pdf may be of interest if you do not already have it. The water injection is downstream of the seals for obvious reasons. Rge seals are cooled by the water and the flow from the engine ensures the tube is always filled with water while the boat is being powered

 

[Bandit]

they are not meant to leak.

 

[ianc1200]

So they will generally run a bit cooler as the calorifier takes some of the heat away. Rydlyme flush never a bad thing though. What temps are you running at? Impellers been checked / replaced?

It's this engine, with the calorifer, which runs hotter. The previous owner said they should be running at 83 - 95C (there's a dynatape message on the dashboard to this effect). For the same revs the port will be at 85C, the SB 98C. However a thermal imaging camera indicates both have same temp around the sensor body. The water coming out the back is almost stone cold, but it's the volume and how it comes out (see above) which is different. The Sherwood raw water pumps were taken off and rebuilt in January this year, impellers changed etc.

 

[ianc1200]

they are not meant to leak.

Will call them to discuss.

 

[Plum]

It's this engine, with the calorifer, which runs hotter. The previous owner said they should be running at 83 - 95C (there's a dynatape message on the dashboard to this effect). For the same revs the port will be at 85C, the SB 98C. However a thermal imaging camera indicates both have same temp around the sensor body. The water coming out the back is almost stone cold, but it's the volume and how it comes out (see above) which is different. The Sherwood raw water pumps were taken off and rebuilt in January this year, impellers changed etc.

Hi, have you removed and cleaned the exhaust injection elbows?

 

[ianc1200]

Hi, i think no chemical, pleace.

This way is beter.

Cummins Marine Aftercooler Maintenance

The 6BTA's have two distinctly different types of aftercooler. The 250hp and below have so called "tombstone" aftercoolers and these are in the internal coolant circuit of the engine. Not sure re the 270hp, but 300/330/370 have raw water cooled aftercoolers - as seen in the video. These are a major failure point for the engines. Seaboard Marine are the go to place for Cummins spares and advice. Based in California , I've ordered from them Monday lunchtime and got by Wednesday lunchtime here in UK. Can't see how that is possible but it works. The owner has a forum and he really is the font of all knowledge re 6BTA's and newer Cummins engines. If anybody has an original raw water cooled aftercooler it's highly recommended these be changed.

 

[ianc1200]

Hi, have you removed and cleaned the exhaust injection elbows?

Hi Colin, I think I'd need a crane to get them off! But as I have the feed into the elbow from the HE open at the moment, intend shoving an endoscope camera down to looksee.

 

[Tranona]

they are not meant to leak.

Not meant to leak forward past the seals into the boat, but that is not what he is asking. The have to "leak" water out of the stern tube - where else would the water go? When the boat is in the water the stern tube and seal is below the waterline so the tube is filled with water. When the engine is running there is flow out of the stern tube. When the boat is lifted water runs out of the stern tube.

The water feed is quite normal with each engine feeding its own shaft and a cross feed to ensure both shafts are fed with only one engine running.

 

[Bandit]

I interpret a leak as into the boat.

The cooling water passes out to the sea from the stern seal to lubricate the sternseal and cool it but these should not leak or drip into the engine space.

I spent 2 years looking for why one engine runs hotter, I eventually found using heat guns and temp wrap around sensors that both run at the same temp but the gauges on one engine are not recording the temp accurately.

 

[ianc1200]

I interpret a leak as into the boat.

The cooling water passes out to the sea from the stern seal to lubricate the sternseal and cool it but these should not leak or drip into the engine space.

I spent 2 years looking for why one engine runs hotter, I eventually found using heat guns and temp wrap around sensors that both run at the same temp but the gauges on one engine are not recording the temp accurately.

Nothing has ever come in, it's the flow out I was interested in. But will phone Sureseal to confirm.