This is quite a significant increase in electrical power production for the yanmars which is important for us to take into consideration as full time liveaboards. In our case the Honda’s produce about 12amps of power each at 12v, the Yamahas about 16amps each at 12v and the yanmars 120amps each at 12v. Outboards in general do not produce much electrical power especially compared to inboard engines and their big alternators. This is a category that was very important to us because we are going with a lithium house bank and I will explain why that is a factor in a moment. This anecdotal evidence paired with the fuel capacity of the engines gives a Seawind 1160 lite with Yamahas a ~250 nautical mile range and with Yanmar inboard diesels a ~665 nautical mile range all a conservative estimate.įuel Consumption outboard vs inboard Seawind catamaran I didn’t get any intput from Honda owners, I think because almost everybody who chooses the outboard option goes with the Yamahas. 9-1gph at ~7 knots boat speed this all is an average over real life motoring conditions. I thought it would be a good idea to ask some current 1160 owners about their experience in fuel consumptions so I asked the Seawind owners group and out of a small but reliable sample size it seemed like the Yamaha outboards were seeing 1.5-2gph at ~6.5-7 knots boat speed and the yanmars were. According to Seawind the yanmars use about 70% the amount of fuel than the outboard options. One of the biggest factors in choosing which engines to go with are fuel consumption and range. Diesel inboards are known for their torque and will have considerable more torque than either of the outboard options. The 25hp high thrust outboards have about 60% more thrust in forward than the 20hp Hondas and 70% more thrust in reverse due in part to the fact that the Yamahas divert it’s exhaust out the leg instead of behind the prop in reverse. Hp is Hp at a given RPM but the things that can really fluctuate between these engines is torque and consumption. These may be minor points in the grand scheme of these option decisions but none-the-less things to consider. Would we prefer to have the diesel tanks which are located in the bilge and have extra storage in the lockers in front of the mast or have the gasoline tanks there and more storage in the hull bilges. Lastly, the tankage location is a consideration. could be transferable between all three engines. Additionally, if we chose the outboard option we could also choose the same exact engine for our tender so that parts, spares, filters, etc. In the case of gas outboards we would potentially have the same fuel source as our tender so that our spare fuel canisters could be extra capacity for both our tender or our main engines. In favor of gasoline as a fuel source, some people like the idea of having fewer different KINDS of fuel aboard. Many people argue that having diesel fuel onboard is safer than combustable gasoline which maybe true in theory but between ABYC standards and the quality that all Seawinds are known to be built to, it is unlikely that we would have a problem with gasoline stored and safely vented. Besides the obvious fuel capacity difference there are some other things to think about in this category. The 3ym30 yanmars come standard with about 95 gallon total capacity with each tank being located in the bilge area roughly centered for and aft in each hull. The gasoline tanks total about 71.3 gallons and are located in external lockers just forward of the mast as to be isolated and vented overboard below the bridge deck. The Hondas and Yamahas obviously run on gasoline whereas the yanmars are diesel. We won’t get into exact costs here because they tend to fluctuate from the engine manufacturers and distributors but what we can say is the upgrades to the 25hp high thrust Yamahas costs less than 1% of the base price of the boat and upgrades to the Yanmar 3YM30 inboard diesels costs 6%-7% the base price of the boat.
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