Engine Replacement

Big picture -we replaced the original Yanmar 4JH2E (50 horsepower) with a 4JH4-TE which gave us 25 more horsepower.  The 4JH4-TE is almost a drop in with no modification replacement – the engine mounts are exactly the same and the prop shaft needs no modification.  Lastly the transmission from the 4JH2E will bolt up the the 4JH4-TE with no modifications.



We were in the Alligator River on November 8th heading towards Belhaven and the temperature was rising on the engine gauges. We added water and continued at low RPM. We then noticed a drop in oil pressure, at which time we shut the engine down and checked the oil level, it was low. When we checked the engine oil level in the morning before we left it was normal.   We added oil and noticed some milky sludge around the fill cap and also found the coolant level was low again, at which time we decided to stop running the engine and call for a tow from Boat US. Belhaven Tow Boat US towed us to Hobucken and left us at the fish dock for the night (great service). The next morning Oriental Tow Boat US indicated that they could not tow us to the next district due to weather conditions but could tow us to the Neuse River where we could sail to Adams Creek where the Beaufort Tow Boat US could pick us up. The wind was blowing 25 mph and we cannot say enough positive things about the Oriental tow service. In Adams Creek the Beaufort Tow Boat service picked us up and brought us to Town Creek Marina which is a certified Yanmar dealer. Looking on the internet for Yanmar engine service we thought this was our best option.

Sailing to Adams Creek
Sailing to Adams Creek

We looked for obvious signs of leakage at the marina but could not find any.  We did a compression test and all four cylinders were in spec, so we removed the head and heat exchanger (you can see a milky substance on head where water was mixing with oil.  Both the heat exchanger and head looked OK once removed.  This left us with two possibilities – cracked head or cracked block.  If we sent the head out for repair and everything looked OK then we would have to put the engine back together to to check for a cracked block.  If it turned out the block was cracked then we would have spent thousands of dollars on a trashed engine.

This is where things get interesting.  Sitting in the marina store was an exact replacement engine that would almost drop in Nomad with little modification.  The engine was ‘nearly new’ with only 300 hours on it.  Rather than continue to drop thousands of dollars on  a twenty plus year old motor with 4,500 hours on it we decided to bite the bullet and replace the engine.

The corpse
The corpse

A-Frame used to lift old engine above floor boards

A Frame used to hoist engine
A Frame used to hoist engine

Engine coming out


Dead motor waiting to be lifted out through hatch

Engine lifted out of engine bay
Engine lifted out of engine bay

Empty engine bay


New engine Betsy found sitting at marina store – as fate would have it, and exact match for our deceased one.

New Engine sitting in marina store
New Engine sitting in marina store

New engine installation pictures

Forklift bringing new engine


New engine being lowered through large hatch in front of mast



Captain Randy guiding engine down


New engine in boat


Betsy re-finished the engine bay


New engine back in place





Technical details – – – we have a Sea Frost compressor that allows the engine to cool the freezer and it takes the place of one engine mount.  To run the new engine’s cooling hose we needed to cut a hole for the hose to pass through the Sea Frost mounting plate and drill another hole for an engine bolt to pass through.


Cooling hose passing through front and rear of Sea Frost mounting plate.



Technical details

The new Yanmar 4JH4-TE is taller than the old 4JH2E.  This required getting a sawzall and cutting the corner down so the cooling hoses had enough clearance.  The center support board also needed to be ‘notched’ to clear various engine pieces.


Engine Mods
Detail of area that needed cut back

The height of the new engine also required cutting into the insulation and notching one of the floorboards.



With the increase in horse power we needed to increase the pitch in the prop . . . which meant having a diver remove the prop and sending it to a prop shop .

If you are in Beaufort NC and need prop work we highly recommend Big Rock Propellers.


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Mason 44 – Don & Betsy