Perkins 4.236 Marine Engine Mystery Solved

We were fortunate to have had John Deaton from Deatons Yacht Service, come aboard Banjo and perform an inspection of our Perkins marine engine. Shannon and I have been nervous since discovering a problem with Banjo’s engine.  Since, we have been actively seeking answers to our Perkins 4.236 Marine Engine Mystery.  Today, we realized the extent of the problem and have potentially encountered a major delay in our cruising plans.  Major delay is probably an understatement as we already depleted a large amount of our cruising kitty already this year performing other updates.

Perkins 4.236 Major Delay

Before we relay the findings of this Perkins 4.236 Marine Engine mystery, a little background.  Banjo was re-powered in 2002 with an 85-hp Perkins Marine Engine purchased from TransAtlantic Diesel in Virginia.  There were approximately 4700 hours on the engine in 2018, with no known rebuild having been performed in the 17 years prior.  In the year we have owned Banjo, we have performed checks of the engine on a general schedule, which, in retrospect, was probably not as rigorous as it could/should have been.  I checked the fluid levels a few weeks and ran the engine without difficulty a couple weeks before the start of the issue. 

Symptoms and Fixed Items

As some of you remember, we discovered water, thought at first to be diesel, in the engine oil before Hurricane Florence.    Here is a list of the symptoms we encountered as a part of our Perkins 4.236 Marine Engine mystery: 

  • Engine was hard starting.  It did not immediately start, but took three separate turns of the key to get a start.
  • Banjo was “making oil,” meaning there was more fluid indicated on the dipstick than we could account for.
  • The withdrawn oil was emulsified, meaning the water and oil did not separate after sitting.
  • We had gunk in the coolant reservoir.
  • No external leaks noticed.
  • Once started, we did have coolant water in the exhaust, as expected, coming from the back of the boat.
  • Once started, the engine seemed to run fine.

On recommendation from a few different marine diesel mechanics, we have since:

  • checked the raw water pump (no issue noted)
  • replaced the impeller (no issue noted)
  • pressure tested the engine oil cooler (passed: no issue noted)
  • rebuilt the starter (by product of trying to start the engine)
  • pressure tested the coolant system to rule out a blown head gasket. (head pressure)
The Investigation

John began his investigation by photographing everything and tracing out the system verbally.  Afterwards, his first peered into the heat exchanger, where some rust was noted floating on the surface of the coolant.  The level of the coolant seemed correct.  Next, the raw water pump was examined, but did not seem to indicate a problem.  Moving on, he disassembled the exhaust hoses attached to the engine manifold.  Water POURED out of the exhaust hose onto the deck of Banjo’s engine room.  Immediately, he backed away to let me get some video.  “There is your problem,” he stated, ” and that means you do have water on top of the pistons.”

The Synopsis

According to John, there are a couple things that could cause the engine exhaust system to fill with sea water.  The most obvious is the engine repeatedly turning over without starting.  Whenever the pistons are moving, sea water is constantly drawn into the coolant system.  But the sea water doesn’t get cleared out by the firing of the engine since the engine isn’t started.  There would need to be a lot of starting attempts made in order to draw that much water into the exhaust system. 


The other possibility would require a couple different failures.  First, the anti-siphon valve would have to fail and get stuck open.  In addition, there would have to be a failure of a seal in the raw water pump that allowed water to bypass and push into the system.  If the siphon on the anti-siphon valve did not break the siphon, the engine would continue to cycle water into the exhaust system.  The exhaust system would eventually fill and the water would back up into the pistons.  This is most likely the cause of our issue.

End result, given the time involved, is that there is likely to be corrosion and rust in the cylinders, piston rings, and pistons.  All of the oil channels are likely to have corrosion and there is likely to be emulsified oil all throughout the engine.  We could feel our hearts sinking.

The Plan

Although we could perform a bunch of oil changes in the hope of using the engine as-is, the likelihood of an eventual loss of compression and failure is high.  Given our desire to go cruising where engine services are unreliable or non-existent.  We want and NEED a reliable engine for Banjo!!  There is no chance that we would go anywhere, even locally, until this condition is met.  It is true that Banjo is a sailboat and we can use sails for propulsion, but with her displacement and size, an engine is critical.

John’s recommendation was to disassemble the engine, remove it from Banjo, and have it entirely rebuilt.  Heartbreak.

The estimate to purchase a new engine of similar power to have shipped to the dock would be around $27K dollars.  That is just the purchase price, without installation.  He estimated we could remove the engine, have it rebuilt, and reinstalled for about half of that figure.

This is Boat Life

So as sad as it is to admit, Shannon and I have had to come to grips with the reality that we are likely NOT going cruising this year, or in the near foreseeable future.  Instead, we now have to find a way to pay for the repairs and have encountered a major delay in getting Banjo back to sea.  Looking forward, however, we know that once this has passed, our engine will be fresh and reliable. 

Coming Up

Be sure to follow our ongoing engine repair and boat projects on the rest of our blog.  So it looks like we will be offering many more exciting boat projects in the coming months, be sure to stay tuned.

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