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levenezia 01-15-2005 03:17 PM

engine facing aft with saildrive installation
I''m close to closing on a new boat order with a saildrive. To my surprise, when I inspected the boat,the Yanmar engine is mounted aft of the saildrive. That is, the 3JH faces aft and the saildrive forward.The prop, naturally, faces aft but I was surprised by the set up. Is this a normal installation? None of the photos I''ve ever seen show the saildrive forward of the engine in the boat. Comments would be appreciated.

jkumin 01-16-2005 08:45 AM

engine facing aft with saildrive installation
Both Volvo and Yanmar make reverse saildrives. There is nothing inherently wrong with reversing the leg so it faces aft when installed ahead of the engine. That said, all the usual issues of engine installations and saildrives apply. One is access, much normal maintenance activities take place at the front of the engine, can you get to what you need? If you like the handling in a test drive, have adequate access to necessary areas, and are willing to accept the normal saildrive issues (watch the zincs closely), there should be no reason to avoid this setup.

Jeff_H 01-16-2005 09:06 AM

engine facing aft with saildrive installation
One of the advantages of using a saildrive is that it allows the designer to place the engine either forward or aft of the propellor. The advantage of this is that it allows the designer to have additional space forward of the engine for accommodations and on modern designs, with their center of buoyancy placed further aft than it would be on a more traditional design, it allows the weight of the engine to be placed further aft as well. In the case of a high performance boat it allows the saildrive to be placed further forward where there will be less drag and less disturbed flow reaching the rudder.

Installing the engine facing aft can have its disadvantages as well. It is generally harder to design proper engine access when the engine faces aft. In most applications, using a saildrive generally moves the engine aft in the boat some vs using a conventional propshaft, and so when the engine is reversed, if not carefully considered, having the engine aft of the saildrive can create a drastic need to move other weight further forward, which can create other, sometimes serious, design problems for the designer.

Another issue is the fore and aft mounting angle of the engine. Most engines used with saildrives are designed to be mounted level in the boat or with the output shaft end of the engine mounted slightly lower in the boat. Given the geometry of the aft end of the boat, it is hard not to exceed an acceptable mounting angle without altering the shape of the run of the boat to provide adequate room for the oil pan. This is less of a problem on a larger boat but begins to be a problem on a boat that is small enough to ude a 3JH.

In any event this should not be a deal killer but you should do some homework on the items above relative to the boat in question.


levenezia 01-16-2005 10:35 AM

engine facing aft with saildrive installation
thank you very much for the explanations and response. I think this installation will work fine. Larry

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