The New Engine
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The Perkins 4.154 (62hp) that came with the boat has unknown hours, and parts for 4.154s are getting hard to find.  I stumbled across a deal on a used 4.236 (85hp).  The "deal" was actually for 2 engines - one with a rod-sized hole in the block.  I decided that the cost of fixing up my tired 4.154 and buying all the necessary spares would come close to the price of the used 4.236.  Some useable spare parts could be stripped off the dead engine, resulting in further savings.

The 4.236 was re-assembled quickly to get in in operable condition, then test run sitting on a pallet. It had good oil pressure and sounded like a good engine should, so money was paid and the engine was stripped back down for pressure washing and paining.  Manifolds and anything rusty or crusty were dip-tanked then primed and painted.

The old engine:

old_engine.jpg (84984 bytes) 

The new engine is going to require a new propeller... I got a great deal on a Martec / Seahawk Autostream 6000 feathering prop.  The pitch can be adjusted externally without disassembling the propeller (i.e. a quick snorkel dive), allowing it to be fine-tuned to the engine output. 

Some pictures to show the scale (24" dia prop):

prop_and_carter_feathered.jpg (68251 bytes)  prop_and_carter_open.jpg (65578 bytes)

A new muffler and exhaust hose are also required.  The 4.154 had 2" exhaust, and the 4.156 requires 3" exhaust.  Too bad I'd just replaced all 26ft of the 2" exhaust hose in Mexico last summer...  Ah well...  The routing is going to be the same, and I'll need to glass in a larger thruhull for the exhaust exit thru the transom.  There isn't enough room under the aft berth to fit a 3" bronze thruhull.


I didn't like the original method of attaching the engine mounts - they were lag-bolted to the glassed over wood stringers.  I always try to plan for what might happen should we find ourselves wrong way up, and the engine coming loose from the engine beds would be a very bad thing.  The stringers needed to be lowered an inch for the new engine anyways, so I cut about 3" (after measuring about 100 times to be certain), and will thru-bolt 4" x 4" x 3/8" steel angle sideways thru the stringer, as well as lag bolted into the top of the stringer.  There's 1" of space between the bottom of the horizontal part of the angle and the top of the fiberglass for access so that the engine mounts can be thru-bolted into the top of the angle.

  cut_engine_beds.jpg (73507 bytes)  new_engine_beds.jpg (71636 bytes)

Measurements were made by projecting the shaft angle to the forward engine room bulkead using several different methods - all of which fell within about 1/4" diameter of one another, so must be close.  Fishing line was strung from a horizontal line thru that point back aft at the same angle as the shaft, but offset to either side over the stringers. The transmission and engine rotational axis (centers) are the same all the way through, so measurements from the center of the front pulley and the center of the transmission shaft flange to the engine mounts were reasonably easy.

Update 5-8-04:

The engine room is painted and the new engine beds are done!  I bedded the angles in thickened epoxy to ensure they mated perfectly with the sides of the stringers.   The  (12) 1/2" thru-bolts are shown below, with 3/8"x2"x2" washers on the inboard side.  There will still be (4) 1/2" lag bolts vertically  installed, one near each mount.  This engine isn't going to come loose!

engine_beds_with_angle.jpg (43408 bytes)

Routing the exhaust was "bunches-o-fun"...  There were a total of (8) 4" holes that had to be cut to get to the engine space.  The first few had to be cut at ~45 degree angles thru 2x4s with very limited clearance for tools.

running_exhaust_hose.jpg (45544 bytes)

A 45 degree fiberglass elbow was glassed into the transom where the old 2" bronze fitting was located.  The new routing of the hose keeps it up high and level so it'll be self draining.  The old routing dipped under the steering quadrant so water would sit in the hose.  A rubber exhaust flapper on the exit will keep following seas from finding their way where they shouldn't.

engine on beds.jpg (64616 bytes)    engine assembly with kids.jpg (77639 bytes)