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Renewal of exhaust system in old boat with Perkins 4-107 Part 1

Magnus Hultin

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I have struggled since june 2012 with finding root cause to having water in the oilsump on my sailing vessel, a 1967 Finnrose 37. We are located on the swedish westcoast south of Gothenburg.

The engine is a marine fitted Perkins 4-107 with a Bowman heat exchanger, which cools both the freshwater and the engine oil in two compartments.

The problem is now solved but I though I could share the story on this forum, and many thanks to Charlie W who have contributed with guidance and good ideas.

My first suspision was the heat exchanger, as I had changed all O-rings during spring 2012. I took it apart and cleaned all surfaces throroughly before carefully putting it together again. After this I changed oil 3 times running the engine warm in between, and changing oil filter before third fill. Everything looked fine at first but after beeing away from the boat for a week the oil was watermixed again. Back to square one.

I dismounted the seawater pump to check if water could find its way in along the drive axle, but dismissed this theory as the drive axle on my jabsco pump is rotating in the open in between the pumphouse and the engine block.

Discussing with one of my brothers, he suggested the water could come in backwards through the exhaust system. To check this theory I loosened the exhaust manifold and found salt water dripping from the gap between cylinderhead and manifold.

We had found at least the source of the water. Next step was to find out what to do about it.

Knowing little about marine exhaust systems I found that we had a water jacketed stainless system all the way from the engine to the gooseneck in the aft of the boat. The total length was approximately 5.5 meters devided in two parts, with a joint midway where the seawater was by-passed through a rubber hose. This system had been in use during 45 years without any issues, but evidently we now had water leaking from the outer jacket-pipe into the inner exhaust pipe.

This is how it looked:

Seawater injected to the jacket-pipe after passing the heat exchanger.



Stainless jacketed piping passing a lowest point before continueing towards the goose neck in the aft.



The gooseneck and a 45 year old Elastomuffler, a Canadian product no longer available, but in remarkably good condition.



We made 2 attempts of repairing the existing system after identifying small but significant leakage in the rear part of the system, but we still found water filling up through the exhaust and into the manifold. This was late summer 2012 and we decided to put the boat on land and think it through over the winter.

After setting the vessel in the sea again spring 2013 I started to sketch out a new system and the only realistic option cost wise was to go for wet exhausts. The problem in a sailing vessel with the engine as low as ours is to find enough space below engine to fit a waterlock with the required capacity. After reading lots and lots of articles with guidelines on the subject and dicussing with a number of boat engine mechanics, I found a doable way of routing the system in a way requiring a waterlock with a worst case capacity of 8.5 litres.

I bought the parts needed and started the work.

The first part, and one of the trickiest, was to get the old system out of the boat. As said it was in two parts, but the large part closest to the engine was to long to get out in one piece. Aparently it was put in place prior to the interior being built.

An electric hack saw was made to work hard a good hour and it took a couple of blades.




Next part was to convert the engine end of the old piping to a water injection elbow. My brother had a guy at his work who welds in stainless and we had him do the conversion after drawing out our general idea of how it should look. Here it is mounted to the exhaust manifold.



From the engine side



The waterlock is same type as a typical Volvo Penta muffler, a large rubber hose with endpieces in stainless steel, where the exit pipe bends internally to the bottom of the tube. Placing this big piece in our boat was a real challenge but we finally found a cavity below the propeller shaft, where the waterlock rests on both hull sides in the rear and on the end wall of the engine box in the front.



Part 2 to follow.....
 
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Part 2 to follow.....

Here comes part 2 of the story....

The Waterlock from above with the hose (Vetus) attached between water elbow and waterlock.



From the waterlock the exhast hose goes along the starboard hullside into a the rearest end of a sleeping bunk, where it goes vertically to its highest point.




Rear of the bunk the hose drops about two feet to create a goose neck and then has a fall of cirka 10% towards the old Elastomuffler which acts as a second silencer and also prevents water from being pushed into the system from the outlet through the hull side. Next picture is from the rear end and the highest point can be seen in the other end.




The system was fitted and thoroughly test run before our summer vacation and during a 10 day sailing trip along the swedish west coast we had some proper motor legs where the engine ran in march speed (1800 rpm) for periods up to 6-7 hours. No rubber parts of the system gets more than hand warm. I am very happy with the result.

And again, thanks to Charlie W for bearing with me.

Magnus Hultin - Onsala Sweden

Some pictures of the boat. It was made for my parents in 1967 and they used it for almost 40 years. My brothers and I are trying to keep it going.



 
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