A/C raw water pump

[tonyiiiafl]

I would agree, this was factory, and I would rather replace with a March

[Midnightsun]

I went to the MarinAire site and looked up their recommended flows. Their 16,000 is 400 gph and the 11,000 is 250gph . Pretty close to what you are running now, minus 1000 btu. Comes to a total of 650 gph recommended flow for 27,000 btu. Like I said, 750 is more than enough.

The flow on AC units is not very critical, easily seen at the marina where some seem to throw water 5 feet horizontal where others barely clear the hull. Not sure what I have but its not very big as water flow is rather weak out of the 3 outlets.

True story, AC died on my previous boat and was not able to get a pump for over a couple of weeks during some nasty hot weather. Went to the local pet shop and purchased an aquarium pump as a temp fix for less than $100, worked perfectly. Those little pumps are pretty decent, have a salt water tank which I started in May of 2011, 24/7 pumping 250 gph, original pump still works fine after 10 years. This is not an endorsement to do the same.

Here is a good example of a very high quality magnetic drive pump @ 480 gph. Remember, these are meant to run 24/7 so they need to be well made. https://www.aquacave.com/blueline-20-hd ... world.html

Here you can see the choice is rather huge. Some of those bad boys will do 9,000 + gph. If it said "marine" on those units, just multiply the cost by 10 and you will be in the ball park. https://www.aquacave.com/catalogsearch/ ... avestate=1

[tonyiiiafl]

Big thing is ignition protection

[Midnightsun]

Yes ignition protection is a big factor however not all AC pump units are located in the engine compartment and I do not think this applies to diesel applications. My biggest gripe is you can get twice the quality for 5 times less.

[tonyiiiafl]

I don't put enough engine hours on for diesels at this point, so my pump is in the engine area with gas 454's. HOWEVER, we are retiring in a few years and we plan to stay up in Cape Cod Area for spring, summer and fall, then off to Florida, Bahamas, and the Keys. I am currently looking for a 44 to 50 Carver down there that needs a repower. I formally owned a trucking company, and there were a lot of promotions for engines. Buy 6 trucks with a certain engine and get a free one on the floor on a skid. I was/am a (retired from the trade) diesel mechanic who knows the older Detroit 2 strokes intimately. I have 2 6V71TTA silver series in my possession. They were rated at 350HP each, and I was able to get them set up as 400 HP. Wasn't too interested in anything higher like J&T does with their 6-71's. Heck, that was a 246HP highway engine set up to 475! They don't last too long at that HP. Anyway, my goal is to find a pristine hull that is in need of repower that my Detroit's will find a home and not to worry about ignition protection. Just have to find it!

[km1125]

Source of the post How many GPH is the pump that is there now ? If it works properly then just replace with the same whatever that is...if it is not working efficiently then an upgrade would be wise.... be aware in this case, more is not better as in heat exchangers the important thing is contact time to transfer heat...it can be over done.

In most cases that's a misnomer.

With more fluid flow you transfer less BTUs/gallon of coolant, but you're flowing more coolant so it usually more actual BTUs that get exchanged. In the cases where that doesn't happen (like when someone removes their thermostat), it's not the increased flow that's the issue, it's that you disrupted the normal flow pattern so much that certain areas don't get cooled at all.

[bud37]

Source of the post

Source of the post How many GPH is the pump that is there now ? If it works properly then just replace with the same whatever that is...if it is not working efficiently then an upgrade would be wise.... be aware in this case, more is not better as in heat exchangers the important thing is contact time to transfer heat...it can be over done.

In most cases that's a misnomer.

With more fluid flow you transfer less BTUs/gallon of coolant, but you're flowing more coolant so it usually more actual BTUs that get exchanged. In the cases where that doesn't happen (like when someone removes their thermostat), it's not the increased flow that's the issue, it's that you disrupted the normal flow pattern so much that certain areas don't get cooled at all.

That is true but a lot depends on the circumstance and specs for the system you are considering.....but in the context of this thread I believe it would be wise to stick with close to the original spec as that was the design. There is a reason they spec a particular GPH for their system efficiency IMO and experience. Contact time is affected by turbulence and fluid velocity, but that goes way beyond the discussion needed here. There is piping size, hose restrictions, power needs, wiring etc to consider if one were to oversize the system gph too much, and like I said ..it can be overdone, meaning not to go too far for no reasonable gain.

[Midnightsun]

Like I said, it is not that critical. Think about this for a minute. 60 degree water circulating or 90? Depends on where you boat and the time of the the year. Systems are designed for use everywhere in general and do not have flows or dedicated designs for different temps/locations. Just like your home heat pump, Can be used in down south or in winter conditions. Obviously not as efficient when at extremes.

[Viper]

In general terms, it really depends on the system and what inputs it uses to cycle on and off; pressures, temps, ambient conditions, and where these are taken. There are tolerances and ya the system will work if you move away from the optimal equipment spec, you'll just change the efficiency curve. The difference may be measurable but not felt. Whether the difference is felt or not will depend on how far off spec a mod has taken it. It's a double edged sword, you don't want your mods to cause short cycling or unnecessary extended running to get to a setting.

No matter how high you go with your pump spec, you're only going to move a certain amount of water through a given size of condenser tubing. You might change pressures and volume a bit depending on the pump but eventually it will reach a point where it can't push any more even if it hasn't reached it rated output. While this might tax a typical pump with a mechanically/shaft driven impeller, the good thing about the ones we use for this application is that they're magnetically run. If rated output is restricted, it's not that big a deal on the pump.

[tonyiiiafl]

Well, I bought the KoolAir PM1000-115. In my humble opinion it is a POS. Reviews were mixed. It is SO SO Noisy! I want to stick with the 1000GPH as it will match my 1” input hose spec, rather than step down to 3/4”. I have contacted the seller who is in FL for return. If not I will have to file a case with EBAY under their return policy. I guess I will spend the extra $100.00 and get the March.