Outboard engine charging circuit question

[LiftyK]

A friend of mine has a sailing boat with an outboard engine. He used to charge exclusively via solar as his old engine had not alternator fitted. He’s just bought a brand new Mercury 5hp four stroke engine that came with charging capability, accessed via a simple two pin plug.

When collecting the engine from the dealer, my friend asked if a load (battery to be charged) should always be connected. The dealer gave a strange look as if this was a strange question. I know normal inboard engines should always have a load connected.

Q1: is it normal to be able to run an outboard fitted with an alternator but with no battery to charge?

My friend had meanwhile connected the engine output to his solar panel circuit, instead of connecting the solar panel, as a temporary measure. When I asked, he confirmed that the connection was upstream of the solar regulator. He also told me that no charge was being received.

Q2: would you expect an outboard engine charging current passed through a solar regulator to deliver any charge?

As the solar panel voltage would be much higher that the outboard charging voltage I would not expect charging to work.

I advised my friend to make a direct connection from outboard to boat 12V battery and measure the current with a DC clamp meter.

Thanks for your advice on his setup.

 

[Alex_Blackwood]

A friend of mine has a sailing boat with an outboard engine. He used to charge exclusively via solar as his old engine had not alternator fitted. He’s just bought a brand new Mercury 5hp four stroke engine that came with charging capability, accessed via a simple two pin plug.

When collecting the engine from the dealer, my friend asked if a load (battery to be charged) should always be connected. The dealer gave a strange look as if this was a strange question. I know normal inboard engines should always have a load connected.

Q1: is it normal to be able to run an outboard fitted with an alternator but with no battery to charge?

My friend had meanwhile connected the engine output to his solar panel circuit, instead of connecting the solar panel, as a temporary measure. When I asked, he confirmed that the connection was upstream of the solar regulator. He also told me that no charge was being received.

Q2: would you expect an outboard engine charging current passed through a solar regulator to deliver any charge?

As the solar panel voltage would be much higher that the outboard charging voltage I would not expect charging to work.

I advised my friend to make a direct connection from outboard to boat 12V battery and measure the current with a DC clamp meter.

Thanks for your advice on his setup.

Q1 yes. Q2 No. The solar panel is not designed for it. That is the simple answers. TBH. I doubt if you require anything more in depth.
Your advice to your friend is correct.

 

[jwilson]

Most smallish outboard charging coils deliver AC at varying frequency : fine for powering nav lights directly, but you need DC for charging a battery. You need a rectifier to convert the AC to DC if you want to connect to a battery.

 

[shanemax]

jwilson is so correct. I purchased a regulator/rectifier from Ebay, a 12 volt one which was designed for a motor bike. about £20-£30 and it works perfectly and has done for years. There is no positive negative coming from the outboard as its A/C. The outboard power is perfect for lights but will blow anything else. In fact it can blow 12 volt bulbs as the faster the engine goes the higher the voltage.

 

[Alex_Blackwood]

jwilson is so correct. I purchased a regulator/rectifier from Ebay, a 12 volt one which was designed for a motor bike. about £20-£30 and it works perfectly and has done for years. There is no positive negative coming from the outboard as its A/C. The outboard power is perfect for lights but will blow anything else. In fact it can blow 12 volt bulbs as the faster the engine goes the higher the voltage.

The OP says it has a charging plug. Some outboards do have charging as well as lighting coils He will have to double check. I assumed, possibly wrongly, that he knew what he was saying. Says something about assuming!

 

[shanemax]

Sorry but just a thought. you need a 12volt rectifier/regulator. if you have two wires from your outboard you need a 4 wire regulator /rectifier . The two yellow (normally yellow) goes to the outboard either way round and the other two,which should be green/red go to your 12 volt battery. Obviously Red to positive. At a reasonable rev you will probably get 2-4 amps.

 

[shanemax]

Having read Alex Blackwood perhaps it already has a rectifier /regulator installed. Get your multimeter, if its pumping out about 14.2 volts and does not climb much when reved it has one installed but if reeved the voltage climbs up to 18-19 then it needs one.

 

[B27]

Some small outboards have recifiers and regulators built in these days.

Having read Alex Blackwood perhaps it already has a rectifier /regulator installed. Get your multimeter, if its pumping out about 14.2 volts and does not climb much when reved it has one installed but if reeved the voltage climbs up to 18-19 then it needs one.

Also check ifi ti's AC or DC coming out!

 

[Graham376]

A friend of mine has a sailing boat with an outboard engine. He used to charge exclusively via solar as his old engine had not alternator fitted. He’s just bought a brand new Mercury 5hp four stroke engine that came with charging capability, accessed via a simple two pin plug.
Thanks for your advice on his setup.

Presumably the engine came with a handbook/instructions, what does that say?

 

[VicS]

If the engine spec is with an output for battery charging then it will have a rectifier fitted. It may not be a regulated output.
As said a check with a multimeter will confirm the output is DC or, heaven forbid, even read the manual.

The solar panel will remain the best bet for charging the battery on a small sailing boat because the output from a small outboard is quite small and only effective while it is running, which is hopefully very limited.

It is correct to connect the outboard directly to the battery but fuse the connection and be very careful not to get the polarity wrong or you will toast the rectifier instantly.
Also avoid disconnecting the battery while the engine is actually running .

 

[CliveF]

I bought my Honda 6 hp with a charge coil and it comes ready to go, complete with water proofing plug for the socket on the engine when no battery connected.
MY MANUAL states for my engine you can run with or or without a battery but this must be decided whilst the engine is STOPPED! with the dire warning "DO NOT REMOVE THE CHARGING LEAD WHILST RUNNING THE ENGINE IT WILL DAMAGE THE REGULATOR"

I suspect yours will be the same but as others have said the manual should tell you.

Good luck

 

[shanemax]

Main question is how old is it. If its new it probably has 14.2 volts coming out DC regulated. If its an old but good one it may be produce power straight off the fly wheel magnets. ie AC current. I have a very reliable 20 year old Yamaha two stroke 9.5hp and and also a very reliable 20 year old 15 hp two stroke Johnson but they are both AC straight off the fly wheel. Before we get any comments about two strokes they are marvellous engines, light weight and did you know all those containers ships berthed up at Felixstowe are two stroke and will burn more in a quarter of a mile than you could burn in a life time and once out of territorial waters burn heated crude oil/heavy oil by the ton.

 

[PaulRainbow]

Main question is how old is it. If its new it probably has 14.2 volts coming out DC regulated. If its an old but good one it may be produce power straight off the fly wheel magnets. ie AC current. I have a very reliable 20 year old Yamaha two stroke 9.5hp and and also a very reliable 20 year old 15 hp two stroke Johnson but they are both AC straight off the fly wheel. Before we get an comments about two stroke they are marvellous, light weight and did you know all those containers ships berthed up at Felixstowe are two stroke and will burn more in a quarter of a mile than you could burn in a life time and once out of territorial waters burn heated crude oil/heavy oil by the ton.

From post #1 "He’s just bought a brand new Mercury 5hp four stroke engine"

 

[Gsailor]

Posts 10 and 11 have it concluded imho.

My guess is a multimeter will show approx 14.5v DC coming out of the engine.

On my first boat it was so and I either used it or didn’t.

It was not always enough to keep the battery charged and back in those days it meant taking the battery back to shore for a charge.

 

[shanemax]

I remember the good old days when you had to take the battery home for a boost charge. I bought one of those electric cool boxes, back in the day, very good they were too but I woke up in Walton marina with two flat batteries, cos I hadn't protected the starter battery , so had to put my hand in my pocket and buy a new one from the chandlery.

 

[Refueler]

"once out of territorial waters burn heated crude oil/heavy oil by the ton"
Actually not true anymore .... many sea areas are now Low Sulphur fuel areas and over last 10years or so - ships have been converting fuiel tanks over to Low Sulphur Marine Gas Oil ......

The days of burning Crude went out the 'porthole' many years ago ...

 

[William_H]

A major export from here (well 1500k N of here) is liquified petrolium gas. Huge tankers with great insulated tanks carrying thousands of tonnes of low temperature high pressure LPG. The ships run on (you guessed it) gas that boils off during the voyage (to Japan etc). Yes they have to leave some on board for return journey.
re original question. Yes I and Vic know all about 1980s Johnsomn lighting circuits. But things have changed I imagine. Still if geeneration is from coil under flywheel as it used to be thne charge will be variable with engine speed. But a battery needs a voltage above 14v to take any charge so only an MPPT type regulator can do anything for low revs. (very unlikely) So read the manual it might have a rectifier built in, it might have a regulator built in but don't be too hopeful of any useful charge. ol'will

 

[Snowgoose-1]

I have a circa 2012 Mariner 6hp 4T Sailmate that came with charging. The output is tiny and probably designed for electric start to top up a motorbike type battery.

Perhaps things have changed since then . I enjoy starting mine by hand and have ditched the electrical output for solar energy.

 

[Refueler]

A major export from here (well 1500k N of here) is liquified petrolium gas. Huge tankers with great insulated tanks carrying thousands of tonnes of low temperature high pressure LPG. The ships run on (you guessed it) gas that boils off during the voyage (to Japan etc). Yes they have to leave some on board for return journey.

My last ship with Shell .... LNG from Brunei to Japan (85.000 cu.m) :

She ran on 'boil off' and we were required to burn 1 mt of Fuel Oil per day as well ... but that was soon stopped.

 

[shanemax]

"once out of territorial waters burn heated crude oil/heavy oil by the ton"
Actually not true anymore .... many sea areas are now Low Sulphur fuel areas and over last 10years or so - ships have been converting fuiel tanks over to Low Sulphur Marine Gas Oil ......

The days of burning Crude went out the 'porthole' many years ago ...

This is why I said territorial waters as these container vessels carry two types of fuels. One they burn out at sea and one they burn when they get to Europe or America. The sea fuel has to be heated as its so thick it will not flow unless heated. The low sulphur fuel they use near continents with emission rules.