A4 in MD

**carbonsoup** · 09-19-2012, 11:54 PM

engine update

Oil pressure has been getting pretty low lately, so I changed the oil and replaced with 40wt. After running 20 minutes in gear, it seems to keep 20psi under load, about 10psi higher.

Compression test today as well. (Not sure about accuracy of the tester as the threading was longer than that of the spark plug. So, the spark plug adapter O-ring didnt seat onto the cylinder head, thus the only thing maintaining pressure would have been the threading (+plus the oil that I put on). Do you think this would make much of a difference?)

#1. 95 psi, plug slightly dark (rich)
#2. 85 psi, plug perfect
#3. 90 psi, plug dark tan (lean-ish)
#4. 75 psi, plug tan (lean) w/ deposits

**carbonsoup** · 09-20-2012, 06:52 PM

compression test instructions!

ok, so i didnt read the compression test instructions that said to open the throttle all the way...

my buddy with an A4 in his Tartan 34, who loaned me the compression tester, did a check yesterday on his motor and found the difference between having the throttle all the way open and idle was 15-20 psi higher.

I will recheck when i get a chance.

**joe_db** · 09-21-2012, 01:21 PM

Enough batteries to do what an A4 and 20 gallons of fuel can do would sink your boat. Are you SURE you want to do this?

**carbonsoup** · 09-23-2012, 01:10 AM

Originally posted by joe_db View Post

Enough batteries to do what an A4 and 20 gallons of fuel can do would sink your boat. Are you SURE you want to do this?

not sure i agree with that, but no im not sure, not really, however if faced with a 3k rebuild at the end of the season.... the A4 goes and new technology gets to try.

also, as a fabricator and someone who has built an electric moto and researched a bit on the subject of electric conversions... with about 5300 lbs displacement 6 'quality' marine batteries could power the boat for 4-5 hours @ 5 kts. I would consider this pretty good range for a single day with a recharge... i understand that if one were to take a multi-day trip a recharge is not an option, however, I would temper this with 'I bought a sailboat, not a motorboat'. that being said, recharging with regenerative and solar is not going to get you to 100% by the next day... meh, means i need to sail more...

another point of the batteries... you could spread them out anywhere in the boat, instead of 400 lbs in the stern.

**Sony2000** · 09-23-2012, 07:18 AM

An inexpensive conversion can be using a golf cart motor setup of 48 volts or more, and a propeller off a diesel.

**ndutton** · 09-23-2012, 09:01 AM

Carbon,
Please keep the details coming during your conversion, this is very interesting. I understand electricity can be a viable propulsion system depending on boat usage. It isn't for me but that doesn't deter my curiosity.

Potential issues I'd be considering:

Management of hydrogen gas during recharging
Spillage containment of sulfuric acid
Reaching Catalina after a dead calm crossing with dead batteries
No hot water when I got there (from another thread)
EMF's affecting the compass and/or autopilot fluxgate
Expected useful life of the batteries. What is it, 5 years for lead-acids? 500 cycles for lithium (which has not been mentioned for this application)

edit
The power to claw myself off a lee shore in the worst conditions. In this case I equate reserve battery capacity with sufficient fuel.

I have a customer who just got an all electric BMW car. I evaluated the electric utility's analysis (read: propaganda) and for him it clearly was a financial loser. He was 12 years away from breaking even on initial expense vs. anticipated savings over a fueled car and this did not account for bi-annual battery replacement ($ouch$). Presenting this I asked why?

He said, and I really respected his position, well somebody has to do it, why not me?

**ernst** · 09-23-2012, 12:11 PM

You say,

"6 'quality' marine batteries could power the boat for 4-5 hours @ 5 kts."

I have researched electric conversion a little bit and everything I have found says that this is entirely unrealistic.

Do you have data that supports this statement? What kind of batteries are you talking about? What is their capacity (Amp hours), how much is usable (without damaging them; I believe for standard deep-discharge flooded cells it is about 50%), what is the current required to drive your boat at 5knts?

I am skeptical but I would love to learn something new.

**sastanley** · 09-24-2012, 12:08 PM

Cool!

I have a friend in my sailing club that added an electric motor to his originally outboard powered Olson 29. This is considered one of the early ULDB type boats on the West Coast, but has actually proven to be a great performer that has held up very well. I think total displacement is somewhere in the 3,500-3,600 lbs. range.

I am pretty sure he is running at 48 volts, and has the motor attached to a saildrive. The boat originally had an outboard, but he got a 3 second PHRF credit for the inboard/saildrive install and it wasn't a smelly diesel.

They were intially thinking they were going to get a range of 45-60 minutes, but have found their realistic range to be much better..Haven't talked to him in much detail other than that. I'll inquire further.

Like any engine, it seems the power consumption goes up exponentially for minimal speed gains as we near hull speed. Take a knot off your 5 knot cruise speed (20%) and your effective range goes up way more than 20%.

Neil, I have all the same concerns you do, however, given the recent pile of threads here about bad fuel & untimely shut downs, I am glad I have a mast with sails as a backup.

**joe_db** · 09-24-2012, 03:18 PM

Against a decent wind and chop, it can easily take full throttle to maintain 5 knots with my boat. Assuming that is 25 HP, we can translate to 18,850 watts. So say we use a 48 volt motor, that would be 392 amps. Assume we have 4 8D batteries, which are 220 amp-hours or so. Assume we discharge them to 2/3 so as not to ruin them, that would be about 24 minutes run time.
Now assume flat calm and say 5 HP for 5 knots or so. That would give 120 minutes run time by the math.

This is 667 pounds of batteries to run 1/2 hour. I can run say 20-24 hours between refueling usually, so batteries to do that would weigh a LOT

If you need to get in and out of a slip, this could work out. Taking one trip from memory, Cape May to Staten Island with no wind.....not so much.

**sastanley** · 09-24-2012, 04:10 PM

joe, thanks for posting those numbers..I did not do ANY math, I was just guessing.

I'll also comment that 'renewable' sources like solar and batteries and all that I think are really cool..the reality is that most of the time we still need some form of dino juice to get them (re)charged

Gas/diesel is still too cheap to be replaced in most scenarios..for now.

**Carl-T705** · 09-24-2012, 07:39 PM

It's been done

A Pearson Commander has done this conversion. It's posted on the Pearson Ariel website. He sails Lake Minnitonka in MN and only plans on using this for short intervals. It's a interesting read.

**carbonsoup** · 09-29-2012, 02:39 PM

math

Originally posted by joe_db View Post

"Assuming that is 25 HP, we can translate to 18,850 watts. ....by the math".

Firstly, i am excited that you guys are interested in this, if nothing more than some thing to read about. I will be posting a conversion thread on the Pearson Ariel forum once i get started in earnest with research and planning, but I just wanted to start with a comment on Joe's post about the math on wattage conversion from gas to electric. A simple conversion is not possible for the inherit difference in torque curves between the two motors:

(A) an electric motor has 100% torque at 0 RPM and the A4 has a, um, err, a non linear power curve, so an 'equivalent' 3 kwh electric motor would be more than enough for a 5500 lbs boat. So, what does a 3 kwh DC electric motor equal.... not sure, by by looking at some of the available electric motor conversions would seem to point around 9 hp.

(B) An electric motor needs no transmission but the A4 has a transmission which has a potential loss of 20% power.

(C) Whats the hurry? The energy required to push a boat through the water at hull speed (my boat is just shy of 6 kts) versus crusing at 4kts may be more than double. So, when you consider traveling at Wide Open Throttle on the A4, and this i am assuming would be about 25hp, versus just over Idle might be 4 kts.... on an 'equivalent' electric motor i 'could' go more twice the distance.

and on a tangent, would you really want to subject your 40 year old A4 motor, regardless of a recent rebuild, to 100% throttle for more than an hour? even in an emergency? a electric would have no issue with this scenario.

As I said I will be researching this more throughly and will put some more solid numbers for everyone to debate... once someone buys my A4... ha.

**joe_db** · 09-29-2012, 07:33 PM

HP is HP and you may well need a transmission if your electric engine does not spin at a boat-prop friendly RPM. If the prop is spinning at 2500 RPMs and you want 10 HP or 20 HP, the torque HAS TO be 21 or 42 ft-lbs. The math is the math. If your electric engine either by nature or gearing can max out at 2,000 or 1,500 RPM, you can gain efficiency by spinning a larger prop. Also note the A4 is direct drive in forward, so there are no gearing losses.

The other thing is the expected use. We left Cape May with fuel in jugs on deck and ran full throttle all the way to New York City once. I also recall needing every bit of power we had to make an anchorage during hurricane Charlie. So for me.......I always wish I had more power and more range. It is entirely normal for us to make 60-70 miles on a no-wind day to get someplace we want to be.

* here you go:

This product is no longer available.

http://www.alibaba.com/product-gs/520090952/5KW_72V_2800RPM_motor_for_electric.html?s=p

This product is no longer available.

5 KW at 2800 RPMs. Should do OK with an A4 prop. You'll need 72 volts for it.

Originally posted by carbonsoup View Post

Firstly, i am excited that you guys are interested in this, if nothing more than some thing to read about. I will be posting a conversion thread on the Pearson Ariel forum once i get started in earnest with research and planning, but I just wanted to start with a comment on Joe's post about the math on wattage conversion from gas to electric. A simple conversion is not possible for the inherit difference in torque curves between the two motors:

(A) an electric motor has 100% torque at 0 RPM and the A4 has a, um, err, a non linear power curve, so an 'equivalent' 3 kwh electric motor would be more than enough for a 5500 lbs boat. So, what does a 3 kwh DC electric motor equal.... not sure, by by looking at some of the available electric motor conversions would seem to point around 9 hp.

(B) An electric motor needs no transmission but the A4 has a transmission which has a potential loss of 20% power.

(C) Whats the hurry? The energy required to push a boat through the water at hull speed (my boat is just shy of 6 kts) versus crusing at 4kts may be more than double. So, when you consider traveling at Wide Open Throttle on the A4, and this i am assuming would be about 25hp, versus just over Idle might be 4 kts.... on an 'equivalent' electric motor i 'could' go more twice the distance.

and on a tangent, would you really want to subject your 40 year old A4 motor, regardless of a recent rebuild, to 100% throttle for more than an hour? even in an emergency? a electric would have no issue with this scenario.

As I said I will be researching this more throughly and will put some more solid numbers for everyone to debate... once someone buys my A4... ha.

**ndutton** · 09-29-2012, 07:47 PM

Might want to have a look at this electric powered Catalina 30 R&D platform in Santa Barbara:

Page not found – Reliable Penguin

http://www.propulsionmarine.com/catalina-30-showboat-with-electric-drive

A4 in MD

A4 in MD

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