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Repowering "Frolic" 30 with Kubota Diesel
by Tom HughesYankee 30 "Frolic"

 I have almost finished repowering my Yankee 30, from an Atomic 4 to a three-cylinder Kubota which is dimensionally identical to the older Universal M25XPA diesel engine.  In my case the new engine mounts fit on top of the existing Atomic 4 engine bed.  The old Atomic 4 was mounted in the bilge and over the keel.  On the port side, the front and rear engine flange containing the mounting holes were lug bolted to the fiberglass liner/engine bed.  On the starboard side, a steel L-bracket is through bolted to the fiberglass liner extending into the bilge.  The new engine mounts, low profile, cast aluminum mounts, were lug bolts on the port side to the old engine bed/liner and the starboard side engine mounts were through bolted on top a a 1/4 inch shim, on top of the old steel engine mount.  This brought the propeller shaft up 2" to line it up with the transmission output flange.

My installation will be complete when I finally replace the old 12 x 8 propeller will my new 15 x 10 one and when I build a new top to my engine cover so I no longer have 2 inches of new engine plumbing sticking out of the cover.  Good luck with your conversion, I think mine was worth the expense $$$ and the four months of weekend labor to install it.

Tom Hughes
Yankee 30 "Frolic"
Half Moon Bay, CA

UPDATE!!
Tuesday, September 29, 1998
Subject: Installing a diesel engine
Hi Steve and Bill,

This weekend was the first time I fired up my new Kubota diesel since  installing it in Frolic.  Boy it sure sounds good! Loud too.  My three-cylinder Kubota engine has a Barr marine conversion kit from 1980, both which were not previously installed.

Dimensionally, this engine is identical to the Universal M25 engine.  This engine mounted on top of the  Atomic 4 engine bed using some aluminum lower profile engine mounts and the  expansion tank and injection tubes stick up just under three inches above  the current engine cover height.  If I were to buy a new diesel engine, I  would get the Universal M3-20 which is marketed as an Atomic 4 replacement  and is over two inches lower, from the top of the engine to the propeller shaft, which is the most critical dimension for Yankee 30s.  This would give you more leeway when modifying the engine cover and might just fit under  the existing one.  I plan to attach a one inch thick closed cell foam pad to the raised engine  cover with a fabric covering to match the existing cushions.  This should  bring the cushion height about even with the existing four inch high foam cushions.  I assume that Bill has a dinette cabin layout as I do.

Ah, the exhaust system was the other Abatross around my neck.  I put a Vetris waterlock directly under the engine.  I had just under nine inches of  clearance and the waterlock is 8 5/8" tall.  It was the only aqualift muffler that would fit in this location.  I led the exhaust from the port side manifold through a galvanized street 90 to a SS mixing elbow with a 45 degree bend down toward the starboard side of the transmission lever.  I have a 12" section of exhaust hose with a fiberglass 90 and another 8" section of exhaust hose into the waterlock muffler mounted under the engine.  I then have one section of exhaust hose exiting the muffler and passing  through the original exhaust opening in the bulkhead and leading up to  another fiberglass 90 degree elbow pointing toward the port side and connected a long section of exhaust hose following the original exhaust  routing to the transom tube.  I wanted to reroute the exhaust through the bilge to the transom but I could not fit any muffler in the bilge area aft of the engine, so I followed the original exhaust routing.

Well, this is the most I have written about the engine swap to date. I guess I could use this as a starting point for a report.  I am kicking myself for not taking any "before" pictures, but will be happy to take after photos.  I hope this info helps.  Feel free you contact me if you more questions.

Later,  Tom Hughes

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