Diesel Re-Power Questions

[1970Columbia34]

We were are making a nice new upgrade in the engine department. We are removing our Palmer P-60 and replacing with a remanufactured Yanmar 3gmD, with a Kanazaki Km3V v-drive, with at gear ratio of 3.20 to 1. I have a few questions that maybe some of you can answer. One being the exhaust our current exhaust set up has a heat exchanger (for hot water heating) that will be removed as it won't be needed. On the Yanmar with a V-drive the exhaust is going to exit towards the bow, does exhasut have to slope downward the whole distance tell it exits to work properly. I have included pictures of our motor, our exhaust set up, diagram of our exhaust and a picture of a Columbia that had this conversion made (very nicely done and my insperation). Thanks for all the help anyone can provide.

Scott

[citation34]

Why not keep the exchanger?

[r.furborough]

No, the exhaust does not have to slope down all the way, but there are rules that need to be followed for an exhaust system that is safe and will not kill the engine.

Rather than type out everything, check out this link

http://www.betamarinenc.com/exhaust%20systems08oct.pdf

[1970Columbia34]

Good point on the heat exchange no real need to remove it I guess seems to work really well.

Thanks for the link to the exhaust diagram so in your opnion do we need to do anything really diffrent with our setup we have a muffler (not waterlock) but before we get to the exhaust we have a large upward look you can see in the pics and diagram ( the loop should prevent water from pushing back up into motor, since thats the purpose of the water lock muffler correct?

Scott

[r.furborough]

The design if the exhaust system is more important to you when the engine is off and water is not being driven out of the system by the exhaust gases.

Unlike a power boat a sailboat can still be underway when the engine is off, it heels, has waves hitting the transom in a following sea and water can be forced into the system and into the engine particularly if there is residual water in the system. A loop that rises as high a possible or an expansion chamber can overcome this.

A waterlock also acts as a muffler, but more importantly it is at the lowest point in the system between the engine and the loop or gooseneck/expansion chamber at the transom or wherever the exhaust exits above the waterline. It is a collection point for water left in the system when the engine stops and is sized not so much by the engine but also by the volume of the pipes connected either side of it.

It is possible for water to siphon in exhaust systems, to prevent this at siphon- break is utilised between the heat exchanger and raw water injection point, the siphon-break should be raised above the waterline to be effective.

Water getting into the engine is bad, really bad, very tiny amounts cause corrosion of valves and cylinder wall, small amounts can cause a hydro-locking when it gets into a cylinder and when the engine is cranked will prevent the piston from reaching TDC, if the engine cranks it can bend con-rods and you are into a re-build or replacement of the engine.

Atomic 4's and Palmer P60's are low compression gasoline engines, in the order of 8:1 - 9:1, diesel engines on the other hand are compression ignition engines and have compression ratios of 20:1 or more, so in some respects the importance of good exhaust design is more important for a diesel.

I hope this helps.

[1970Columbia34]

I am assume we should be good then cause we have a large upward loop that goes up a good 3 feet or more above the water line before it drops back down and exists the boat. To make the connection from the new motor to the current metal exhaust, what kind of exhaust pipe can I use, does it have to be metal or can it be some version of high temp rubber? Thanks

Scott

[r.furborough]

You can use marine hardwall wet exhaust hose that meets SAE J2006 as long as the raw water is injected before the hose. As you are installing a V-Drive and your exhaust is going to exit forward on the engine I would recommend a convoluted flexible type and it bends easily and is capable of a tighter turn radius. Of this type, the Vetus made hose is the most flexible but it is also quite expensive.

[1970Columbia34]

So if I use a rubber type hose it has to have raw water running throught it for it to hold up correct? Where as if it were a metal exhaust I can put my raw water in at any point in the exhaust system.

Scott

[JimsCAL]

Originally Posted by 1970Columbia34

So if I use a rubber type hose it has to have raw water running throught it for it to hold up correct? Where as if it were a metal exhaust I can put my raw water in at any point in the exhaust system.

Scott

Correct. You need metal exhaust (insulated) until at least the point of water injection, then hose is fine after that. Hose is easier to install and makes replacements down the line much easier. Note that the exhaust loop, not the waterlift muffler is what prevents water from backing up into the engine.

[kaluvic]

I've had a better look at your pictures....I see the big dry loop and think this is OK.

A couple concerns might be:
1) Insulation...the union looks un-insulated and fairly close to the FG.
Also looks like the horizontal "muffler" is not insulated....what would happen if something laid across it? Would it melt/burn?

2) Vibration....is there a flexible section between the engine and the "muffler"?