I have just taken delivery of a new BV2203 for installation in the 41' voyaging sailboat I am construction. I am currently working out the details of the exhaust system and have a few questions. First, though, some details: The engine will be located under the pilothouse floor, below the waterline and near the center of the boat, so there will be a long exhaust run to the transom (168"), with a relatively high lift (54").
My first question is what diameter exhaust hose would you recommend for this installation, considering the increased back pressure the long run and lift introduce? Centek's recommendation was 3"ID, which seemed significantly larger than comparable installations I've seen. What do you think?
My second concern, again a result of the relatively long run and high lift, is keeping exhaust water from backfilling the engine. All plans I've see recommend a riser (and flapper valve) at the transom (A) to keep following seas from fill the exhaust hose. Because of my accommodations plan I have to run the the exhaust hose close to floor level through the aft stateroom, which means, once the engine shuts down, a fair amount of water will fall back from the transom riser to the waterlift muffler and engine--from my calculations, more than muffler can handle. In some pilothouse designs, I've seen the addition of second riser (B) off the outlet of the waterlift muffler to prevent this. Is this a sound design? I've read that you should aim for a combined lift of no more than 42" from the bottom of the waterlift muffler to the transom exit point, but there seems to be some debate about this point. In my design, I would be well above this. What is your recommendation?
Best regards, Collin
____ Building Galene Facts & reflections on building a 41' voyaging sailboat from a bare hull
This looks like a very interesting project and I hope that you will occasionally post updates so we can all see how you are progressing.
As far as the exhaust systen is concerned I do agree with Centek. I would use 2" from the engine to the muffler and 3" after the muffler. The extra size of exhaust will help to keep the back pressure down to acceptable limits because of the length of the exhaust run. This can easily be done using a Vernalift (Centek) style 4 waterlock #1500112, which has enough capacity for your needs. Centek will, on special request, build a special muffler with the different size hose connections.
Although you could get by with 2-1/2" after the muffler, it is often to difficult to find 2-1/2" mufflers, hose and thru-hulls.
I will recommend a Vetus gooseneck for your loop at the stern. This basically provides an expansion chamber so it is highly unlikely that water that enters the tailpipe as part of a following sea will pass over the hump. A flap style transom exhaust fitting will then give you the piece of mind.
Thanks for the info Stanley, it is a big help. I do have a couple of followup questions.
In my installation I have room to add an in-line muffler (such as Centek's Vernatone), several feet after the waterlift. What is your experience with these? Do they offer much added noise reduction? Do they add significantly to the back pressure problems? Although I realize this is a rather subjective question, are they worth the added cost and complexity?
Secondly, as this is a project boat, it may not hit the water for another two+ years. What kind of ongoing maintenance do you recommend to keep my new BV2203 healthy until I put it into regular service? One mechanic recommended starting it up every 4-6 months. He suggested I could remove the impeller from the raw water pump and run it safely for 3-4 minutes without the raw water feed. What are your thoughts?
Best regards, Collin
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Building Galene
Facts & reflections on building a 41' voyaging sailboat from a bare hull
The Vernalift waterlock muffler is all that you will need and the in-line muffler wont make any difference in your installation. The exhaust tail pipe will be almost totally quiet and often the water coming out of the exhaust thru-hull makes more noise than the exhaust beat.
I agree with your mechanic who advised that the engine needs to be run every so often but I dont like the idea of running it without any raw water supply. The heat from the exhaust is likely to damage your new exhaust hose. I suggest that you use a bucket and let the raw water pump suck the water up from the bucket. Just use a hose pipe to replenish the bucket contents. If you are in an area where it freezes in winter, please remember to use some anti freeze (RV potable stuff) in the raw water circuit. The other alternative is to drain all water from the raw water system including the exhaust muffler.
Do not under any circumstances connect a hose pipe to the raw water pump as this can cause problems.
