Reply
 
Thread Tools Search this Thread Display Modes
 
Old 04-18-2021, 04:24 PM   #1
Veteran Member
 
Sykes's Avatar
 
City: Dania Beach, FL
Vessel Name: Godspeed
Vessel Model: Bruno Stillman 42
Join Date: May 2019
Posts: 49
AC looses prime when underway

Seems to happen when i am in any bit of a sea. 3 foot sea and it stops working. Any suggestions?? Sending this message while underway...
Sykes is offline   Reply With Quote
Old 04-18-2021, 04:59 PM   #2
Guru
 
CaptTom's Avatar
 
City: Southern Maine
Vessel Model: Prairie 36 Coastal Cruiser
Join Date: Dec 2012
Posts: 2,717
Not uncommon. Those pumps lose their prime easily. Apparently a bit of air is getting into the intake.

On one boat I had, a planing hull, I put a "T" in the pump intake, with a pipe straight up well above the waterline and a cheap plastic ball valve at the top. Whenever it lost prime, I'd open the valve to release the air.
CaptTom is offline   Reply With Quote
Old 04-18-2021, 05:16 PM   #3
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,185
Certainly common enough. As said you can put in a priming valve to make it easier to reprime.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 04-18-2021, 05:21 PM   #4
Technical Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
Mine has that problem, mostly 3-4'+ seas. My solution was to put a switch on the lower helm that when "ON" the pump runs continuously, not cycling with demand from the AC's. The fix works.

When the AC's cycled off, it would get a little air with each wave, then when it restarted it had a mouthful of air. If on continuous, it can handle a little air with each wave.

The switch also makes it easier to reprime, the AC's can be off but pump on.
Ski in NC is offline   Reply With Quote
Old 04-18-2021, 05:52 PM   #5
Guru
 
rgano's Avatar
 
City: Southport, FL near Panama City
Vessel Name: FROLIC
Vessel Model: Mainship 30 Pilot II since 2015. GB-42 1986-2015. Former Unlimited Tonnage Master
Join Date: Oct 2007
Posts: 4,984
I did two things. One was to add a forward facing scoop to the exterior of the hull. Two was to add a Yandina bubble extractor after the pump BubbleOut.
__________________
Rich Gano
FROLIC (2005 MainShip 30 Pilot II)
Panama City area
rgano is offline   Reply With Quote
Old 04-18-2021, 07:55 PM   #6
STB
Guru
 
City: Gulf coast
Join Date: Aug 2016
Posts: 2,271
My own preference would be to move the intake farther back (but not so far back that the props cause a problem) and to use a forward facing scoop (if it isn't what is there now) to give it some assist and avoid any suction when the water is passing by fast.

Basically, I'd want to locate the intake away from air, protect it from suction, and give it some help getting water in to widen the tolerances.

Adding things like valves and air traps may help, but my own preferences is to avoid adding parts. There is an old saying in software, "Novice programmers add corrective code; experienced programmers remove defective code." Increasingly, I've been trying to apply the idea, a.k.a. "The KISS principle", to my boat.
STB is offline   Reply With Quote
Old 04-18-2021, 08:34 PM   #7
Guru
 
CaptTom's Avatar
 
City: Southern Maine
Vessel Model: Prairie 36 Coastal Cruiser
Join Date: Dec 2012
Posts: 2,717
Yes, a good once-over of the whole system should identify any weaknesses in the design. Obviously in an ideal world these would be engineered away.

Personally, I'm OK drilling one less hole in my boat, and using a priming valve. Funny thing, I'm dealing with this right now on one of my air conditioner intakes. It's a massive 1-1/2" seacock, reduced down for the A/C, and it's not in a great location. I'll be making improvements, but for the seacock I'm stuck with what I've got.

Quote:
Originally Posted by rgano View Post
I did two things. One was to add a forward facing scoop to the exterior of the hull. Two was to add a Yandina bubble extractor after the pump BubbleOut.
OK, I had to check it out:


OMG that's just an "air can," AKA high-vent, for a hydronic heating system. $14 at Lowes.

Even in the fresh, nearly oxygen-free water of a home heating system, these things fail within a few years. I can't imagine putting them in a salt water system. I don't know what the attachment on top is, so I'll defer any further judgement.
CaptTom is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 10:33 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012