Combined Partial Summary of ZRD responses
ZRD manufacturs a 24vdc 15KW DC Genset (48vdc available via transformer). ZRD does not desire to discourage you, but we know first-hand and from former prospects (not customers) that electric propulsion is NOT the way to do it. Unfortunately, the best way is still a diesel engine connected directly to a propeller. DC should run everything on a vessel (including 120vac equipment via inverter) except for propulsion. Technology has not been developed yet to drive a boat efficiently by all electrical means.

Depending on how you word it or what ratios you like to use, running from a diesel engine directly (skipping Tx for discussion) to a prop is 5-10 times (500-1,000%) more efficient than an Electric motor driving a prop when you include the energy required to recharge the battery bank. Also the time before a battery bank is 100% exhausted is from 1 hour to a few minutes depending on the speed used. This speed is almost certainly considerably less than Direct Diesel Engine propulsion. Hybrid may be an option, but it has its own problems. The HP output of 1 gallon of diesel far exceeds the AH (amp-hour) output of 600+pounds of battery (1,000ah @ 12volts). I can move 28,000lbs of boat for 5 miles @ 10mph on a gallon of diesel. A 600+ pound battery bank would be 100% gone before that point were ever reached. When 1,000ah of battery is the size & weight of a flashlight D cell, then we will be there, but certainly not now.

The luxury land based automobiles have vs. marine based transportation is not a parallel to be considered. In addition, the 100% electric cars coming on the market now have 1/16 to 1/8 of the distance capabilities of gasoline vehicles. Even then they do not have a 10 minute stop for refueling - requires overnight. For going to work (if not far) or the grocery they are usually OK, but try and take a trip over 100 miles - and most vehicles now can go 450-800 miles on a tankful of gas. That same scenario in a boat is typically less than an hour of operation or 5 miles - whichever comes first. And that is at idle power. Put the engine up to high speed and the batteries are usually dead in 20 minutes.

ZRD's first interaction with all-electric was a number of years ago with a customer purchasing 18 batteries for his all electric 18' Duffy motor boat - basically an oversized dingy. The 18 batteries had combined total of 1,980 AH at 12vdc of power - Duffies are currently set up at 48 vdc, but using 12vdc for ease of explanation. He showed me how far he could go at idle (2-3mph) on the water when he pointed to a bridge approximately 2-3 miles away. He was never sure he would make it back before the batteries were exhausted and dead. He never used full throttle (6 mph) or he would not even make the bridge. This glaring reality of what it takes to move a boat electrically was an eye opener.

ZRD recently had a lengthy phone and email conversation with a gentleman looking for a custom DC Genset to power his 33foot all electric sailboat - He removed his diesel propulsion engine and went all electric 5 years ago. He said he is one of the few sailors that actually sails his boat vs. motoring - He stated it was because he had to regardless of weather conditions because he could only motor for 20 minutes before he needed to "plug-in". He is resigned to using his electric power only for in and out of marinas as he docks - Never underway. Some days he only gets a few miles when traveling - depending on wind speed and direction. He left Canada on the Great Lakes, traveled NE on the St Lawrence River, entered the Atlantic and came down the east coast of the US. He contacted ZRD as he passed FL. He is now evaluating going back to diesel propulsion at considerable expense.

Combined Partial Summary of ZRD responses
The Total number of batteries (12vdc 255AH each) required to supply 24KW is greater than 12 (@ 100% eff) with a 50% Discharge for 30 minutes. If kept going for an Hour (not recommended on a regular basis) they will be 100% discharged and risk permanent failure. The Total number of batteries (12vdc 255AH each) required to supply 24KW is greater than 24 (@ 100% eff) with a 50% Discharge after 1 hour. Based on the above, it will require two alternators running @ full output in excess of 13 hours each to recharge. This situation is conducive to premature alternator failure. Massive cooling would be required to assist in their longevity. A ZRD dedicated 24v DC Genset capablle of 500 amps is the only possibile solution - even then there may be problems. The alternator used on this DC Genset is not available to be used as a second (dual) alternator on your propulsion engine. The propulsion engine was not designed for the side loading and will cause engine failure.

Hybrids work, but why do it at all? Hybrids when necessary or required are justified, but not just to do it - especialy on a pleasure craft. When you consider it only adds $$$$+ to the price. At the current stage of technology, it is just Hype. Do not confuse please vessel Hybrid with DC electric propulsion of the type used in Trains or on the pods of large vessels like the Queen Mary 2. These are a form to themselves not available or applicable to the average boater.

Prospect's Reply
First I will explain why we do not want to use a genset. As you know, all over the world the new trend is green vessels. Our boat operates with both engines runing most of the time with the transmission in neutral. During this time we would like to use this power which is wasted by the engines.

This went on for weeks until reality was finally able to be understood.