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Old 08-12-2014, 07:14   #1
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Generator install

In trying to prepare for cruising, I've decided that a Diesel Gen would be nice to have.
For various reasons it looks like I'll be dong the install myself, it will be mounted with it's bottom just above waterline with the muffler bottom just above the waterline.
Question is, do I need a vented loop? What determines the need of a vented loop? Any harm in having a vented loop if it's not needed? I don't worry about running the electrical and fuel etc., but admit I'm no expert with marine wet exhausts.
Generator will be the little 3.5 Nexgen
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Old 08-12-2014, 07:46   #2
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Re: Generator install

Each manufacturer, in their installations manuals, will call out the details and requirements based on above or below waterline mounting. As an example, see this Fischer Panda manual and go to page 63.
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Old 08-12-2014, 07:49   #3
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Re: Generator install

You need to hire a qualified marine whatever for your installation (sorry, that seems to be becoming the standard answer around here).

The vented loop doesn't do anything good for your exhaust, it increases back pressure on the engine. What it does do is keep water out of the engine and boat when the engine isn't running. So, will your exhaust port be above water in all conditions of trim, sail, and sea? If you can answer yes then technically you don't need a vented loop. But, if your heeled waterline, in a good sea, will put the exhaust port below water then you should have one. There's lots of opinion around on how high above the waterline you need to have everything before you do away with the vented loop, but it really depends on each boat, how she sails, how much heel...

https://www.tidesmarine.com/pdf/VentedLoop_Install.pdf

http://www.northern-lights.com/media...t_drown_me.pdf
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Old 08-12-2014, 07:59   #4
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Re: Generator install

I am going to offer an opposing thought as I was about to go down the same route. After a deep discussion with a very qualified marine electrician here are his thoughts:- how often are you really going to use this very expensive generator? For a fraction of the price fit a 2 or 3 klw inverter/charger, a couple of 100 watt or above solar panels and a Wind generator and if possible a second alternator (for me this last is not an option) and you have most bases covered and not using expensive diesel. You have always got the engine as backup and should be run once a day if possible.
So I am not installing a diesel generator!
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Old 08-12-2014, 08:05   #5
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Re: Generator install

Are you talking about a vented loop on the intake cooling water ?

If so, then YES ,!!!!

On the exhaust, not a good Idea......, water lock muffler looped above the water line then over board . This also depends on where you are exhausting the generator .

As was said before , let a marine mechanic take a look at your application and see what he has to say

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Old 08-12-2014, 08:06   #6
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Re: Generator install

Quote:
Originally Posted by Dsanduril View Post
You need to hire a qualified marine whatever for your installation (sorry, that seems to be becoming the standard answer around here).
That was the intent, and it was going to be a dealer recommended by the gen manufacturer, but a few things have come to light as well as a 25% install cost escalation that has made me change my mind. I believe they really don't want this job. I generally do all my own work, once in a blue moon I don't and those times it seems I have to go behind others and correct their work. Just wasn't looking forward to a month or two of weekends installing a genset as opposed to sailing is all.
Seems from the links you posted that a "vented loop" is a siphon break for the raw water cooling side and not the exhaust anyway?
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Old 08-12-2014, 08:13   #7
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Re: Generator install

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Originally Posted by Dsanduril View Post
The vented loop doesn't do anything good for your exhaust, it increases back pressure on the engine.
I can't imagine how a vented loop increases back pressure on the engine. It is installed somewhere between the raw water intake and the water injection into the elbow. The water line exists anyhow, it is just a vent that is added to it. It isn't part of the exhaust system at all.

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Old 08-12-2014, 08:17   #8
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Re: Generator install

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Originally Posted by a64pilot View Post
Seems from the links you posted that a "vented loop" is a siphon break for the raw water cooling side and not the exhaust anyway?
Yes, the vented loop is in the raw water side. The exhaust hose merely loops above the waterline (at all heel levels) before exiting. The vented loop in the water line will prevent siphoning from the exhaust, but it won't prevent water being shoved into the exhaust and to the engine if the muffler/hose is not sufficiently above waterline.

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Old 08-12-2014, 08:26   #9
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Re: Generator install

Quote:
Originally Posted by typhoon View Post
Are you talking about a vented loop on the intake cooling water ?

If so, then YES ,!!!!


I guess I don't understand this. I certainly do not have this on my generator. How can generator water pump draw water in via a vented loop? Won't it just suck in air through the vent?

I have vented loops on my head discharge lines. Nowhere else. (edit: and bilge pump outlets). I have seen them recommended between pump and bowl for inlet water on heads, but never actually seen them installed that way. Seems they need to be downstream of a pump (i.e., subject to positive pressure when pump operating) to even work.
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Old 08-12-2014, 08:40   #10
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Re: Generator install

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Originally Posted by colemj View Post
Yes, the vented loop is in the raw water side ... It is installed somewhere between the raw water intake and the water injection into the elbow. The water line exists anyhow, it is just a vent that is added to it. It isn't part of the exhaust system at all.

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My raw water line does loop to above water line before discharging into the exhaust elbow. The loop is not vented however.
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Old 08-12-2014, 08:40   #11
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Re: Generator install

Put a vented loop on the seawater line between the engine and exh elbow. It's cheap insurance.

After the muffler run the exhaust hose straight up as far above the water line as is practical then down to the discharge, again this is cheap insurance.


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Old 08-12-2014, 08:41   #12
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Re: Generator install

Quote:
Originally Posted by colemj View Post
I can't imagine how a vented loop increases back pressure on the engine. It is installed somewhere between the raw water intake and the water injection into the elbow. The water line exists anyhow, it is just a vent that is added to it. It isn't part of the exhaust system at all.

Mark
If you're putting in a vented loop then you have a loop or rise in the exhaust hose, making the hose longer and creating a water lift situation. A straight, horizontal exhaust hose will have lower back pressure.

------

And yes, with an exhaust vented loop the vent is installed on the pressure/pumped side of the cooling water system. This allows water to flow through the vent system to the exhaust during engine operation, keeping hot exhaust gases from entering the vent. When shut down the anti-siphon valve still allows air into the exhaust hose.
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Old 08-12-2014, 08:59   #13
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Re: Generator install

Quote:
Originally Posted by AndytheSailor View Post
I am going to offer an opposing thought as I was about to go down the same route. After a deep discussion with a very qualified marine electrician here are his thoughts:- how often are you really going to use this very expensive generator? For a fraction of the price fit a 2 or 3 klw inverter/charger, a couple of 100 watt or above solar panels and a Wind generator and if possible a second alternator (for me this last is not an option) and you have most bases covered and not using expensive diesel. You have always got the engine as backup and should be run once a day if possible.
So I am not installing a diesel generator!
I intend to stuff as much Solar above my Dink on the davits as I can, but I'm most likely going to have an AC watermaker and just in case the panels are not enough or we get a hot, buggy night or whatever, I want a genset, but it will be intermittent use, not one that runs all the time.
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Old 08-12-2014, 09:06   #14
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Re: Generator install

Give joe at sound marine a call. I have bought 2 beta engines from him and he is a wealth of information and has a vested interest in DIY like me in doing it right so as not to damage expensive new installs. I have talked to him about a generator and I believe he Handles the Nextgen brand. He's up north but ships to anywhere I think. Chuck


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Old 08-12-2014, 09:31   #15
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Re: Generator install

Quote:
Originally Posted by Dsanduril View Post
You need to hire a qualified marine whatever for your installation:.............
I agree. If the people you are dealing with don't want to do the work, find a qualified installer who does.

Getting this right takes quite a bit of skill and knowledge. A mistake could be a real problem.
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