Info required for Perkins T6.354

[JOHNPEET]

Hi all,

Apologies for posting here and the practical boat owner forum.

Just wondering if a anyone can help me out with some info that I need for the above engine.

I'm putting in new exhaust systems in my steel boat and the supplier of the water lift muffler requires the following so that he can size the pipe work etc and ensure I don't exceed the max exhaust back pressure.

I need the following:

Exhaust gas temp
Exhaust gas flow rate
Raw water flow rate
Max exhaust back pressure - this is the only one I can find in the original manual and is quoted as being 13"WG

Any advice would be welcome

John

 

[volvopaul]

From memory all the 6.354 are on 4 inch exhaust hose .

 

[JOHNPEET]

Hi VP.

The boat is an aft cabin layout with engines mounted mid ships. Ideally the exhaust would drop down and run under the aft cabin floor and then rise up to form a high loop just prior to exiting at the stern just above the water line. Centekindustries are sizing it all up and are a bit twitchy about the arduous route and exceeding the pretty low max EBP

John

 

[burgundyben]

My T6.354 145hp pair ran straight through wet exhausts @ 3.5" diamter.

 

[Latestarter1]

Hi all,

Apologies for posting here and the practical boat owner forum.

Just wondering if a anyone can help me out with some info that I need for the above engine.




I'm putting in new exhaust systems in my steel boat and the supplier of the water lift muffler requires the following so that he can size the pipe work etc and ensure I don't exceed the max exhaust back pressure.

I need the following:

Exhaust gas temp
Exhaust gas flow rate
Raw water flow rate
Max exhaust back pressure - this is the only one I can find in the original manual and is quoted as being 13"WG

Any advice would be welcome

John

Exhaust gas temp. A good SWAG for T6.354 is a maximum turbine out temperature of 400 C at WOT.
Exhaust gas flow rate. Once again another # shooting from the hip would be 300/350 Litres/sec at WOT.
Raw water flow rate. Contact Cleghorn Waring with your Jabsco pump # and they will supply output curve.

Raw water flow with T6.354 is less than more modern engines therefore you can get away with 31/2 inch exhaust tube, but simple rule of thumb is that every 90 degree elbow will cost you at least 1/2 inch of Hg back pressure with this diameter.

From your description your exhaust sounds like an accident waiting to happen, as it will always be full of seawater. When engine not running salt laden moisture will be working away inside your turbine housing and back though open exhaust valve into cylinder. Biggest risk is when craning with seawater sloshing straight back into motor.

 

[JOHNPEET]

Thanks for your replies - much appreciated.

To be honest, I've been thinking long and hard about the best route and I'm struggling to come up with an ideal solution.

The distance from the mixing elbow to the stern is about 3.8m of which 1.3m is in the engine bay. The mixing elbow outlet is about 250mm above the water line.

Another option would be to drop the exhaust into a lift muffler, the outlet then would rise to about 600mm above the water line, pass through the bulkhead into the aft cabin and run down the sides of the cabin at a slope before dropping the last 300 mm vertically before exiting at the stern. My concern on this option is protecting against a wave from the stern, but it guess I could fit flaps of some sort?

 

[Latestarter1]

Thanks for your replies - much appreciated.

To be honest, I've been thinking long and hard about the best route and I'm struggling to come up with an ideal solution.

The distance from the mixing elbow to the stern is about 3.8m of which 1.3m is in the engine bay. The mixing elbow outlet is about 250mm above the water line.

Another option would be to drop the exhaust into a lift muffler, the outlet then would rise to about 600mm above the water line, pass through the bulkhead into the aft cabin and run down the sides of the cabin at a slope before dropping the last 300 mm vertically before exiting at the stern. My concern on this option is protecting against a wave from the stern, but it guess I could fit flaps of some sort?

If your riser is 250mm above W/L it is simply insufficient head. In Pounds Shillings and Pence 250mm is not even 10 inches. To work properly a marine exhaust system HAS to have an absolute MINIMUM spill over point of 12 inches above LOADED W/L. Let's just stop there.

 

[volvopaul]

If your riser is 250mm above W/L it is simply insufficient head. In Pounds Shillings and Pence 250mm is not even 10 inches. To work properly a marine exhaust system HAS to have an absolute MINIMUM spill over point of 12 inches above LOADED W/L. Let's just stop there.

Paul , I love that 12 inch rule, but seriously how many builders adhere to that??? Hardly any, I've sen some real shockers in my time especially on yachts, then again those little sewing machine motors are a throw away item...

 

[JOHNPEET]

Agreed!

Having taken your point on board regarding the "accident waiting to happen" I then suggested "another option" which is a pretty standard layout as shown in the vetus catalogue etc.

On my engines, The exhaust riser leaves the turbo with a 90deg bend upwards, followed by a second 90deg bend pointing aft, followed by a 45 deg bend downwards. Then a straight section approx 350mm long in which the water is injected into the outer void of a twin wall mixing tube before joining the exhaust gas which all told provides about 250mm protection between the turbo and injection point. The outlet of the mixing tube is about 250mm above the water line but I have a virtual free choice of how to route pipe work and what hardware to use to get between this point and the stern 3.8m away, bearing in mind I have the very low max exhaust back pressure of 13" to contest with.

It would have been nice to conceal the pipe work under the aft cabin floor but I accept common sense prevails and all advice is gratefully received.

I've also found some useful info on the Seaboard Marine website which includes a rule of thumb of 200cfm per 100hp for exhaust gas flow rate - need to do the calc yet to compare that.

 

[Latestarter1]

Paul , I love that 12 inch rule, but seriously how many builders adhere to that??? Hardly any, I've sen some real shockers in my time especially on yachts, then again those little sewing machine motors are a throw away item...

How many threads have there been over the years complaining about premature turbocharger failure??

As to little puddle jumper motors installed as auxiliary power in yachts..........No installation policing, at least owner doing a DIY job reads the manual like the OP here, too many so called professionals leave owners with installation which is a poison pill!

 

[R1chB1ch]

Have you considered re-routing them to come out of the sides of the boat mid-ships? I know a couple of people who have done that, not just for the safety element, but on a cost basis when renewing exhaust hose (which isn't cheap!)

 

[JOHNPEET]

Have you considered re-routing them to come out of the sides of the boat mid-ships? I know a couple of people who have done that, not just for the safety element, but on a cost basis when renewing exhaust hose (which isn't cheap!)

The thought had crossed my mind and it's certainly an option!

I can think of a few negatives such as greater risk of fumes entering the aft cabin if port lights are open - particularly when at stand still or slow manovering. There are also many positives especially concerning the overall system back pressure.

Can I throw it open for other opinion from forumites?