Washdown pump causes outboard to lose rpms

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Jday

Well-known member
Joined
May 19, 2020
Messages
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Location
Essex, Md
I've had this problem, especially at trolling speeds, when I use the washdown. It causes the outboard to drop in rpms.
Usually the only other things using power are two hds gen 3, vhf, point 1 gps, fm radio and occasionally a halo 20+ radar.
None of these are affected at all.

This is on a 2004 2120
The washdown pump is a jabsco 4gpm and max draw is 11.2 amps located in the stern port house battery compartment
The outboard is a 2005 200hp optimax.

I have installed a bep cluster 716, the square one, located in stern starboard battery compartment.
Batteries are located at the stern
Washdown switch is original and located in the cabin
Start battery is a 24 800 cca
House battery is a 31 650 cca 225 mins @23 amp

Could this be caused by the length the power has to run from the batteries, to the helm and then back to the pump at the stern? The washdown
pump wiring is original.
Did I simply wire the bep incorrectly?
As I was writing this I went to make sure the pump would only come on when just the house switch was on and that is what happens.. I noticed the emer/parallel switch was on. I must have turned that on at some point and didn't realize I hadn't turned it off.
Would that have anything to do with this?

Any help is greatly appreciated.
John
 
Could this be caused by the length the power has to run from the batteries, to the helm and then back to the pump at the stern? The washdown
pump wiring is original.

That was my exact thought. Wiring not sized correctly. But it is weird that the engine is affected.

I mount a switch in the back under the covering board. This keeps the wiring short...It puts the switch where a mate can get to it, turn it on and not bother the Captain. To me that is important if your true is trained correctly... Captain is navigating to the next fishing spot while the crew is cleaning the decks up.

I had a problem along these lines with a Jabsco Hotshot. It's didn't mess with the engine,but would shut down.
The Jabsco Hotshots are the most powerful, BUT also draw high amperage.

They put out 70PSI ...but call for a 25amp fuse...I guarantee the factory wiring is not large enough.
 
Wart, I had the thought of mounting a switch in the battery compartment. Should I wire it to the battery, or to the bep?
I'd like to be able to turn off everything except the bilge pump at the end of the day.

I'm thinking to the bep. I wouldn't want the pump powered when I'm not on the boat and turning off a switch that's hidden could be forgotten. Clint once said "a man's got to know his limitations".

This pump creates 60 psi and requires a fuse of 20A
Thanks for responding.
What switch do you use?
 
As I was writing this I went to make sure the pump would only come on when just the house switch was on and that is what happens.. I noticed the emer/parallel switch was on. I must have turned that on at some point and didn't realize I hadn't turned it off.
Would that have anything to do with this?

I would guess that this is probably the root of your issue, although why it’s causing the engine to bog down is perplexing. Perhaps it’s a computer control issue caused by the sudden drop in voltage caused by the high amp draw of the pump.

Definitely open the parallel switch, and see if the issue remains. My bet is that with the systems separated, you won’t have that problem anymore.
 
I had a mercury 200hp 2stroke that would bogg down when I hit the trim tabs. The mechanic at my marina said check your battery connections, low voltage will throw the motor into a protection mode. Sorry it was so long ago I can’t remember exactly what he said, but sure enough after cleaning and tightening the battery terminals problem solved
 
Pelagic, I hope to take the boat out this Sunday and I'll be checking that out.
Hotpursuit, you jogged my memory. I have been told and read that the opt's are very power sensitive.
I'll go over those connections this weekend
 
I found some green on the battery connections, none on the bep. Cleaned up the green and set the bep switches to house and start. No problems with the washdown causing the motor to drop in rpms now. Thanks for your help.
 
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