Old enough to know better
Join Date: Dec 2006
Location: Beacon, NY
Thanked 126 Times in 122 Posts
Rep Power: 9
Re: Islander 36 electric inboard? diy
Hi, My name is Oscar Théen and I work at GreenStar Marine. I found our company name on this forum and I thought that a short comment would be in place.
When you come to choosing between a traditional diesel solution and an electric solution you must ask yourself what you actually want of your motor/engine. A diesel solution is for some the best choice and the electric one is better for others.
The electric solution is best for those who prioritize high torque, maneuverability, availability, low maintenance, simplicity, quietness etc. The diesel is best for those who prioritize long transportations at high speed.
Pure plugin boats with our systems usually have a calm weather range at 4 knots of around 30 NM. Full speed is usually around 6 knots. Range at full speed and AGM lead batteries is usually around 6 NM.
We have never installed a system in an Islander 36 but we have installed systems in several boats of similar size and weight. For an Islander 36 I would recommend something like:
Greenstar system: GS18
Battery bank: 8 * GS12-100 Deep Cycle AGM lead batteries
Estimated economy speed: 3 ½ knots in 9 ¾ hours
Estimated full speed: 6 knots in 80 minutes
Note 1. Economy speed for the Islander 36 is probably a bit lower than for the average boat. Economy speed can be increased by changing propeller but that will cost thrust. If a bigger propeller, both in terms of pitch and diameter were to be used there is a risk of overheating the motor at full speed.
Note 2. Runtimes in the Islander example are with batteries that are run absolutely flat which is not recommended. This can be done in case of ”emergency” but usually you should not use more than 50 % of this.
so you are saying that $285 (not greestar, but Power Tech) X 8 = $2280 in batteries alone gives 40 min at 6 knots (so it gets you less than six miles) That is before you even start getting into motor and controller. Now this shows this will not be a cost saver over a rebuild/re-power with Diesel. I really like the idea, and in fact sail on a boat that is electric powered, but done for environmental reasons, not cost. I really like not having to start a combustion engine. Also you say on a mooring, there is no way you are going to charge via solar/wind without spending major dollars. Even on a good charger it will take a couple of days.
Voltage does not matter, it is simple physics.