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Old 11-26-2018, 03:05 AM   #1
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Default 4100 SCR - Add 2nd blower

Hi Folks

I bought a 1998 4100 SCR this past spring and there is only one blower. I can clearly see two lights below throttles in the helm but there is only a single blower and set of hoses. Anyone with a 4100SCR have the same configuration and has anyone added a second blower? I think i may want to do this.

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Old 11-26-2018, 03:11 PM   #2
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What is the current volume of the engine compartment?

What is the flow rate of the current blower?

Either the current blower can turn-over sufficient volume over a given time or it can't.

Recommended Sizing:

<=70 cu. ft = 100 c.f.m. blower
71 to 100 cu. ft. = 150 c.f.m. blower
101 to 300 cu. ft. = 250 c.f.m. blower

You would only need to add a 2nd blower if the current blower didn't have a sufficient CF/M for the space. If you're looking for redundancy, that is a bit overkill, but that is an individual choice.
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Old 11-26-2018, 08:54 PM   #3
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Thanks but overkill for my family's safety is something I'm willing to move forward on. Seen too many boat fires to care about cost. I have read the regulations in the link attached but I'm really more curious on my initial question. Given this is a Maxum 4100 group I was hopeful somebody knew why the SECOND blower light was under the helm throttles. I can't seem to find anywhere in manuals if there were 2 blowers when the boat was built or just one. I know the hoses have to be replaced because they dont seem to reach the bottom 3rd of the bilge but if anyone has added a second blower, that is somebody I'd be interested in hearing from. I dont know the actual square footage and I know I can buy a more powerful fan...they're cheap anyway, but yes, I am interested in a second blower, overkill or not.

https://www.uscgboating.org/regulati...ENTILATION.pdf
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Old 11-26-2018, 11:35 PM   #4
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I'm curious if you have diesel engines? If so that might be the reason for one blower. Otherwise for each gas engine a blower is required. I don't quite understand why you have two switches where most dual blowers set ups just have one switch. Yes by all means get your second blower installed by a professional.


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Old 11-27-2018, 03:46 PM   #5
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I honestly don't believe you understand enough about the concept to blindly assume that "If some is good, then more must be better". (no offense intended)

Regarding CFM, the air intake needs to be sufficient to support the output. You cannot displace more air than you can draw in, regardless of how large a volume the fan can move. Some applications require an intake blower and a discharge blower. If you're not sure how to calculate volume and airflow or whether you really need it, then adding it for the same of utilizing an indicator light is not a great solution.

Mike also brings up a good question. If this is a Diesel, then there is no need for blowers at all. I don't have a blower (diesel). What I have is a panel with an empty breaker marked "Blower". That doesn't mean that it requires a blower.

Finally, the boat fires you witnessed were the result of a fuel leak, not the absence of a blower.
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Old 11-27-2018, 05:00 PM   #6
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"Mike also brings up a good question. If this is a Diesel,"

Don't give me credit for Rogers good question.

I agree with shrews comments. If you draw more air out of the engine compartment that the intakes can replace the engines will starve for air.
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Old 11-27-2018, 05:39 PM   #7
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Quote:
Originally Posted by mmwjr View Post

Don't give me credit for Rogers good question.
My apologies Roger. I agree, credit goes to Roger on that one. Another correction on my (typo):

adding it [a blower] for the sake of utilizing an indicator light is not a great solution.
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Old 11-28-2018, 01:43 AM   #8
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As is the case with a majority of the threads on this site, we need more information than was provided.

How big is your existing blower?
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