A/C Water Flow Adequate?

[Brewbeck]

My 1986 3297 Mariner has a reverse cycle heating/cooling unit. When I turned it on I turned the starting knob to "start", waited 12 - 20 seconds, and then turned the knob to "run." Panel light came on and fan started pushing chilled air, soon reaching 68 degrees (F). I then checked the overboard outlet from the AC unit. I describe the flow as "weak" , barely enough flow for the water to clear the hullside. Is this okay? Other units in my marina have a lot more pressure behind their raw water outlets. Curious, I found the through hull, the sea strainer and the pump. I opened the strainer case and removed the wire basket which contained a small fish and some leaves and some silt. Surprisingly, the amount of water I got through the hose to the through hull was not a lot (I overlooked the shut-off ). In any event, the cleaning made no difference in the flow.

Query: Is my weak flow as compared to the other guys (boats) in the marina significant?
Should I be cleaning the hoses or the through hull, like maybe blowing air through it?
Is it OK to operate with this amount of water running through the cooling system?
Is the 68.5 degree (F) output common and correct?

Thanks for any input, I sure don't want to give up A/C at this time of year in MN.

[Viper]

Source of the post ....Is my weak flow as compared to the other guys (boats) in the marina significant?

I'd say it's an issue. You should have a good stream of water.

Source of the post ....Should I be cleaning the hoses or the through hull, like maybe blowing air through it?....

Wouldn't hurt to blow through the thru-hull in case it is fouled under the hull. It could also be a restriction in your condenser that will require a flushing with a chemical product to clean out any build up in the raw water line of the condenser. There has been a recent thread about doing this very thing.

Source of the post ....Is it OK to operate with this amount of water running through the cooling system?.....

Don't know of any reason why this would be harmful short of increasing system pressures but it would simply get to a point where the system won't cool because the restricted water flow won't dissipate enough heat. If you don't have enough flow, it's not operating as efficiently as it should.

Source of the post.... Is the 68.5 degree (F) output common and correct?.....

That seems fine to me depending on ambient temperature. How long did it take to get there? It will take much longer to achieve if it's not operating efficiently.

Is your AC unit in the flybridge? I ran into this same issue on a Mariner where the owner had replaced the water pump then could never get proper flow. Found that his supplier said the pump was overkill and sold him a lower output unit based on the AC spec however the owner didn't mention that it was on the flybridge. The height of the AC unit needs to be considered to determine if the pump can handle the head pressure.

Has the flow always been this way since you've owned the boat or is this a recent phenomenon? If it's been that way since you've owned the boat, check all the above including the pump spec.

Is the upper Mississippi fresh or salt water?

[tomschauer]

if the unit is not tripping on high pressure, its most likely not a problem. If you are worried about it check the water temperature coming into and going out of the a/c unit. It should be about 10 degrees warmer on the discharge. If its more than 15 try flushing the water coil before replacing the pump.

[buster53]

I sometimes get stinging nettles up into my intake hose. Easy to clear it...I remove my strainer, put my air horn up against the housing and hit the trigger. Whoosh..clog is gone.

[Brewbeck]

Thank you, Tom, buster53 and Viper:

This unit cools almost immediately and maintained the salon at about 75 when the outside temp was 88 and we were in direct sun. Ad to that fact was that we were constantly in and out cleaning.

This is a "new to us" boat; we closed on it last Friday (6/30). It has had no TLC for three years and it shows. Also, there are plenty of deferred cabin maintenance issues as well as gel-coat issues both above and below the waterline.

The pump is in the bilge and close to the through hull for the A/C. When I removed the filter I was surprised I didn't get a flood, but then I realized the through hull is only under about 18". Cleaned it out as best I could while hurrying to get it back of the filter body. This weekend I'll close the sea-cock and give the filter a good cleaning. I also plan to take the compressor and condenser unit out to clean it as well. I'll let you know what happens.