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Discussion Starter #1
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











 

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Discussion Starter #4
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
 

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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.
 

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Discussion Starter #6
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
 

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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.
 

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Discussion Starter #8
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.

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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.
 

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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"?
 

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In the pjoto of the old installation it looks like the muffler is single clamped direectly to a throughull and there appears to be another throughull immediately adjacent without a seacock. I'd correct theses issues on the new install.
 

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Discussion Starter #12 (Edited)
I can add more insulation to the pipe if you think it would be needed. water gets injects back into the exhaust right about the muffler. Yes there is a flexiable section of exhaust between manifold and heat exhanger, when un wrapped its a wheaved mess like metal pipe. think we will be go? do you think we will need a water lift muffler or would it not be needed? the second sea **** you see is for the deck and cockpit drains, both Muffler exit and drains are above the water line should the both have seacocks on them. Thanks

Scott
 

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The old picture shows you inject the water directly above the little black muffler then it goes straight out the bottom...looks sweet to me.

I'd wrap a couple more layers of FG insulation between the muffler and anything that gets hot and call it good.

But that’s the pictures of the old engine.

The new engine looks like it has flexible hose coming off the short riser…that would tell be that the water is injected in that riser and that the exhaust is wet from there on …is that right?

If so this would be a completely different set up then the old pictures which is dry all the way until the muffler.
 

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Discussion Starter #14
that is not our motor but one like we are getting, I will take a look at the motor when it gets here. If thats the case does all the metal pipe have to be converted to rubber or can water flow through the existing metal exhaust?

Scott
 

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Its a fundamental difference in the entire exhaust system.

The basics are to keep the water from getting back into the engine.

The original system looks like it does that well because the water being injected has to get back over that 3ft high dry loop.

Additionally, if you crank the engine for extended periods of time with out it starting (like when you bleed the fuel system) you will not risk flooding the engine.

If you end up with an engine like the new one in the picture, and its water injected elbow off the manifold, it would normally be followed with a water lift/water lock at least 12 inches from the bottom of the engines heat exchanger exhaust opening to the top of the water lift.

I would consider your present exhaust layout as being better…and it may be possible to remove the injection elbow or not have it included (you pay for it) and assemble your original style system.

One thing I would consider is to delete the heat exchanger for the water heater, and replace it with a piece of SS exhaust pipe.
You would normally use the coolant in the engine, not the sea water, to circulate through the water heater.
The new engine may already have an outlet and inlet for this purpose.

I’ll try and attach a drawing that shows two of the most common scenarios…. unfortunately the one you presently have is not show but in my opinion is still the best in you situation.
 

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