FIshfinder shuts off when engine starts - Optimax 150 and Hummingbird Helix 5

dmanmtl

Seaman
Joined
Apr 14, 2013
Messages
63
Something odd happens occaisonally on my new to me princecraft 186. When I start the engine to move from one fishing spot to another the fishfinder (Helix 5 GPS) shuts off and takes a while before it allows m
e to start it up again.

A bit of background - Mercury Optimax 150 (still not sure if I like this animal), 1000 MCA battery (on spec for the motor) All the accessories - bilge, GPS, trim are wired to this battery - which should probably me addressed. Battery is good, cranks the boat over fine.

What I am thinking is happening is that the voltage drops too low to maintain the correct minimum voltage for the finder. I should test this with a meter but have not.

Ideally, I think it would be best to have a 2 battery system - 1 strictly for the engine/ignition and another for the accessories - but I wonder how the accessory battery would get charged if it is not pulling from the alternator. There is room in the battery box for another one.

Thanks in advance for your ideas/comments.

D
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,417
Google..... blue seas system, add a battery kit. Problem solved...
 

joed

Lieutenant Junior Grade
Joined
Sep 28, 2002
Messages
1,132
I think you are correct. The voltage is dropping too low when cranking the engine to keep the finder operating. Could be a weak or too small battery.
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
I'm guessing your fish finder gets its power from the fuse block. Some people with the same problem, have run a separate power wire directly from the battery, to the fish finder, using an inline fuse. Seems to work for most who have tried it.
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
I noticed the same problem this past weekend with my Optimax 125 and my newly installed GX1700 VHF. I am thinking of a Helix FF too, so obviously I gotta find a solution myself!

My opinion is that the battery cables that come standard with the Opti's were penny-pinched by accounting and are just too small a gage. Mine came with 12' 4AWG cables (about 4 feet of which are UNDER THE COWLING, since they wrap all the way around the powerhead before finding their connections!), which allows almost a 10% voltage drop on the 200amp starter draw.

I plan to get fatter battery cables (along with moving my batteries forward for weight balancing vs this bloated pig of a motor, but that's a different problem!).
 
Last edited:

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
The size of battery cables to the motor won't make a difference if the feed that goes to the console comes straight from the battery.

The best thing to do is to run straight to the battery or to the output of a battery switch. If you do go to the output of a switch, the cable size between the battery and the switch DOES make a difference.
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
The size of battery cables to the motor won't make a difference if the feed that goes to the console comes straight from the battery.

I don't know that I agree with that. When you read a (dropped) voltage at the starter, will you not see that same voltage at the battery posts?

In other words, let's say your battery reads 12.4v just sitting there. When you crank, let's arbitrarily say you read 11.2v at the starter (a ~10% drop). If you were to measure voltage at the battery while cranking, would you read 12.4v, or 11.2v?
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
You would read something less because the battery has internal resistance but the battery cable that goes down to the starter has additional resistance. What you measure at the starter will be total resistance of the battery and the cable times the current and what you measure just at the battery is just the battery resistance times the current.

(Rbat +Rcable) * Current = Starter Drop voltage

Rbat * Current = Battery Drop voltage.

In your example, if you started with a battery at 12.4V, you may see 11.8V at the battery and 11.2 at the starter while cranking if the battery internal resistance and the cable resistance were identical.
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,417
In other words, let's say your battery reads 12.4v just sitting there. When you crank, let's arbitrarily say you read 11.2v at the starter (a ~10% drop). If you were to measure voltage at the battery while cranking, would you read 12.4v, or 11.2v?
Probably somewhere in between, but it depends on the wire size and the reserve capacity of the battery. If the wire running to the starter is sized correctly, there will be little to no voltage difference (0 voltage drop) between the starter and the battery until the demand exceeds the reserve capacity of the battery. Once demand exceeds supply, the voltage will drop like a rock. When was the last time you load tested the battery?

In your case, the Helix operates from 10-20 VDC. A fill charged battery is somewhere around 12.8 VDC. To shutdown the Helix your looking almost a 25% voltage drop in battery voltage...Good way to burn up a starter.....

Back in the day (running electronics off a single battery) the phenomenon was a sure sign it was time for a new battery.;)
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
The reserve capacity of the battery has nothing to do with starting current or battery resistance. That is a spec for how long you can discharge a battery.

I never have a problem with my sounder/GPS turning off when I start my engine and it is on the output of a switch connected to the same battery that the engine(7.4L Chevy) is also starting from. I have a second battery but it is totally disconnected from both the sounder and the engine.
 
Last edited:

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,417
The reserve capacity of the battery has nothing to do with starting current or battery resistance. That is a spec for how long you can discharge a battery.
Perhaps I'm using the wrong terminology.
As batteries age their ability to produce and store power begins to diminsh. The same "work" produces higher rates of discharge resulting in lower average battery voltages over time. All fine and dandy until demand exceeds supply and your sounder shuts off from an under voltage condition.
I never have a problem with my sounder/GPS turning off when I start my engine and it is on the output of a switch connected to the same battery that the engine(7.4L Chevy) is also starting from. I have a second battery but it is totally disconnected from both the sounder and the engine.
dependent on the voltage tolerance and current draw of the equipment in question.
Years past, a sonar shutdown on startup was normal. You always started the motor before turning on the sounder.

Better power supplies have for the most part a thing of the past but tolerance varies widely. My Furuno sounder is more sensitive than the Garmin chart plotter and the CHIRP sounder is simply a power hog. 5.5 amp draw.

All on dedicated battery. Would be very surprised if I could get away with anything other than the freshest of starting batteries when starting.

Your displacement is larger but you have a big advantage with your fuel injection and electronic ignition when it comes to starting. No turn the key on a 2.8l 2 stroke that is notorious for being cranky on cold start. Sensitive to cranking rpm to boot. Need full starter rpm for it to fire. Usually hit it with both batteries for good luck.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Perhaps I'm using the wrong terminology.
As batteries age their ability to produce and store power begins to diminsh. The same "work" produces higher rates of discharge resulting in lower average battery voltages over time. All fine and dandy until demand exceeds supply and your sounder shuts off from an under voltage condition.
That is true...and there is internal resistance which increases over time. There is an internal resistance, even when the battery is brand new, which causes a small voltage drop at the battery.

.
Your displacement is larger but you have a big advantage with your fuel injection
No fuel injection...just a carb
 

JASinIL2006

Vice Admiral
Joined
Feb 10, 2012
Messages
5,524
My fishfinder/GPS was wired directly to the starter battery via a fused, fairly heavy wire. Every time we would start the engine, the GPS function of unit would freeze, which was a problem because partly because I rely on the speedometer function of the GPS. The only solution I could find was to isolate the fishfinder/GPS on a separate battery. No problems after I did that.
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
I noticed the same problem this past weekend with my Optimax 125 and my newly installed GX1700 VHF. I am thinking of a Helix FF too, so obviously I gotta find a solution myself!

My opinion is that the battery cables that come standard with the Opti's were penny-pinched by accounting and are just too small a gage. Mine came with 12' 4AWG cables (about 4 feet of which are UNDER THE COWLING, since they wrap all the way around the powerhead before finding their connections!), which allows almost a 10% voltage drop on the 200amp starter draw.

I plan to get fatter battery cables (along with moving my batteries forward for weight balancing vs this bloated pig of a motor, but that's a different problem!).

This past weekend I found out that my VHF shut-off problem came down to a little corrosion on the 30-amp fuse near the battery in the 10AWG main power wire to the fusepanel. Cleaned legs of fuse up with a wire brush, no more VHF shutdown during cranking/starting.

So check that main fuse, too.

(But I still say that the OptiMax stock battery cables are too small a gage)
 

Taupe

Recruit
Joined
Jul 2, 2022
Messages
1
I realize this is a dead thread but there are not any newer ones that I've found, so folks will likely run across this one when researching this issue. I tested the voltage at the input of the fuse panel on my Bayliner, and it went from 12.4V to 8.9V when turning the motor over. Per manufacturer spec the fish finder will reset below 10V.

Since the power to the fuse box is wired directly to the starter on most motors, through the starter relay, you are shorting the circuit when engaging the starter. Cars are also wired this way, notice how your heater blower, dash lights, etc, all turn off when the starter motor is engaged.

TLDR: I ran a 14awg wire straight back to the battery and the voltage only dropped from 12.4 to 11.9 while cranking. The FF no longer resets when starting the boat, which is great since I don't run a kicker motor and spend a lot of time simply floating around.
 
Top