Marine Diesel Engine: Banjo’s Full Story

Perkins 4.236 Marine Diesel Engine Lift Pump

It has been some time since we have posted and, as we draw closer to having Banjo’s 85HP Perkins 4.236 marine diesel engine re-install being completed, we have decided to share the full story. 


Please treat this post as our learning experience, and as a cautionary tale, not as any form of personal attack or bashing.  We realize mistakes happen and sometimes a simple oversight can have disastrous, and expensive consequences.  It is not our intent to speak poorly of anyone, but this IS what happened.  We have elected to wait on posting any related videos at this time, but hope that our story can help others to avoid the same hard lessons.

Recap of Initial Issue

Prior to Hurricane Florence, Banjo’s marine diesel engine  appeared to be “making oil.”  This means that the oil level on the dipstick increased compared to the amount previously in the engine.  Also, the engine would start, but it seemed to struggle more than usual to get moving.  We received recommendations on what we should check, but due to Hurricane Florence bearing down, we changed the oil and got Banjo to safety.

After Florence passed, we changed the oil several times and the majority of feedback we received indicated that we likely had diesel fuel leaking into the oil pan.  I recorded one of these oil changes and the oil was black, but thin.  There are usually three suspects:

  1. Blown head gasket
  2. Cracked engine block
  3. Leaking fuel lift pump

We contracted a couple different technicians to come aboard and assist with the diagnosis.  We ruled out the question of the head gasket by a pressure-test.  There was no way to determine if the block was cracked without disassembling the engine.  Since I was unfamiliar with what a marine diesel engine fuel lift-pump was, we had a skilled mechanic friend come aboard.  He checked a few other items on the engine, including the raw-water pump, the impeller, and the oil cooler to determine if, in fact, it was actually diesel and not sea water in our engine oil.

On the day of Hurricane Michael, we changed the oil and started the marine diesel engine and it ran for nearly an hour with no issues other than the same hard start.  Little did we suspect it would be the last time for awhile.

The Day The Engine Died

The day following the hurricane, we had a local marine diesel engine mechanic come aboard and, as part of the initial diagnosis, he wanted to check the starter to rule it out as the cause of the hard starting.  After making a dismissive comment about the need to close the seawater inlet, he directed me to “over-crank the engine, but not let the engine start.”   Being unfamiliar with the particulars of the engine, and more specifically the sea-water exhaust, I had no idea what consequences of leaving the sea-cock open would have.

I have since learned that most diesel engine technicians, and nearly all engine manufacturers discourage over-cranking.  Engine starters are meant to be used for no more than 15 seconds at a time.  After two attempts, the starter requires several minutes of “cool-down” before trying again. 

I have also learned that our raw-water pump is gear driven which means that with the sea-cock open, anytime the pistons are moving, the engine is drawing in sea-water.  In order to overcome the water-lock and expel the sea-water, the engine needs to start.  Sea-water intakes do not need to be open  prior to starting the engine, as it takes some time for the engine to generate heat.  They can be left closed for a brief time and then opened once the engine has started running, which is a sure-fire way to prevent sea-water from backing up in the exhaust hoses. 

The Moment it Happened

I turned the key and held it, again and again as instructed, but would stop just prior to the engine actually starting.  I noticed that the engine seemed to increasingly struggle with each attempt until, eventually, it stopped turning over altogether.  On the last attempt to turn the engine over I heard a loud pop come from the engine room.  Smoke rose from below, and Chuck told me that I had fried the starter and it would need to be rebuilt.  We posted this afterwards

After the starter had blown, Chuck asked some additional questions and it became apparent how little I actually knew about our marine diesel engine.  He pointed out a few things, such as where to bleed the fuel system, where the oil cooler was, etc., and told me that we would be better to seek the assistance of someone who specializes in diesel engines for further diagnostic help. 

Next Steps

Chuck spent some additional time in our engine room trying to help with the diagnosis. 

He did have some other theories as to what might be going on but that he felt, upon looking at the color of some removed engine oil that we drained at that time, that we likely had sea-water and not diesel which had emulsified in the oil. 

I had no idea that the over-cranking just a few minutes before seems to have been the reason we had the water in the oil and the sample we took was a result of the damage already being done.  It happened just that fast.  In other words, by the time we took the sample, there was water in the oil put there only a few minutes before.

Chuck did seem very knowledgeable, friendly and genuinely interested in helping in our engine education.  And we were left feeling that we were making progress towards finding the cause of our woes. 

Starter Rebuild and Our Next Steps

A couple days later, we took the starter to Squires Auto Generator & Starter Service, and had our starter rebuilt.  I reinstalled the rebuilt starter, here, and we decided to wait before attempting to start the engine until we had someone aboard that could help.  We did not know what was happening and we didn’t want to cause any additional problems by blindly seeking answers on our own. 

We sent a portion of the removed oil off for analysis to determine for certain what exactly was in our oil.  The analysis was to take 7-10 business days.  After 10 days of waiting, we were informed that the sample never arrived to the lab.  It appeared that it was lost in the mail.  Impatiently, rather than repeat the process, we decided to take a trip to Deatons and had the oil cooler pressure tested to determine if it was allowing sea-water to leak into the engine block.  It passed the pressure-tests.   

Since we had just come through Hurricane Michael, we knew there would be a delay in getting a tow as it took some time for boatyard operations to resume.  So we kept Banjo at anchor, and waited.

Tow and Diagnosis

It took about a month and a half for TowboatUS to be able to come get Banjo and take her to Oriental.  In that time, we had not attempted to run the engine.  We were towed to Oriental and, a few days later, John Deaton boarded Banjo to start his assessment.  The first thing he did was release the exhaust clamps and pulled the sea-water exhaust free from the heat-exchanger. 

WATER POURED OUT of the engine.  The original post shows the extent. I sat with a deep sinking feeling in my stomach.  John explained what this meant for Banjo, and us.  He stated that the cause for this level of damage was likely due to over-cranking.  Short of that, the most likely culprit was a failed anti-siphon valve.  I had completely forgotten about the over-cranking that occurred during Chuck’s visit.  Furthermore, I knew I had not ever had to crank the engine prior.  The engine would usually start within one-to-two cranks.  It was not until much later, while reviewing video footage, I remembered that it had even happened. 

Shock and Awe at the Damage

You may be asking how we knew the marine diesel engine flooding occurred when it occurred.  As I mentioned previously, we ran the engine without issue the day before Chuck’s visit hadn’t run it since.  If it runs, then it isn’t flooded with sea-water, even if there may be a some dilutent in the oil.

The engine would have to be removed and either replaced, or we would have to rebuild the entire engine from the ground up.  We waited for the team at Deatons to get the engine removed and disassembled.  It took time to determine if a rebuild was even possible or if the level of corrosion had reduced it to scrap.  The day came and the crew removed the engine and Gary, our Deaton’s liaison and engine specialist, performed the disassembly.  He was able to determine that our original “making oil” problem was due to a failed $100 lift pump.  You can see the original post here.

Perkins 4.236 Marine Diesel Engine Lift Pump
Perkins 4.236 Marine Diesel Engine Lift Pump
Perkins 4.236 Marine Diesel Engine Lift Pump
Perkins 4.236 Marine Diesel Engine Lift Pump
Perkins 4.236 Marine Diesel Engine Lift Pump
Perkins 4.236 Marine Diesel Engine Lift Pump
Costs for Repair and Repair

Estimates for a comparable new marine diesel engine from BetaMarine Ltd in Oriental came in around $22K to be sitting at the dock.  The estimated cost for a rebuild would be in $18K range.  We looked into doing an engine “swap” with Transatlantic diesel for an engine that was already rebuilt but that would cost $10K (plus a core charge of $3K) just for the swap.  The least-expensive option for a swap came from a friend near Winston Salem who could do a swap for $5K (and a $3K core charge).

Finding an Expert for the Long Block Rebuild

If we elected to do a rebuild, the engine would have to be acid-vat cleaned to remove all of the corrosion caused from sitting full of sea-water.  Deatons did not have an acid-tank large enough for this scale of repair and it would have to be sent to another facility who did.

Fortunately, we located Craven Automotive Machining in New Bern, NC who could acid-clean the block and perform the rebuild.  They quoted us $2600 for the parts and labor.  This was half the cost of any engine swap we found and there was no core charge.  

The Rebuild

It took Craven Automotive Machining about two months to complete the rebuild of the engine block and when we saw it, we knew we had made a good choice.  Their work was SUPERB!  

Upon returning the engine to Deatons, the next phase when into action as Gary began the painstaking process of re-assembly.  The marinization packages needed to be reinstalled to get the marine diesel engine ready to test-run.  That test was completed on the shop floor before going through all the effort to move it back aboard.  Finally, the Perkins 4.236 marine diesel engine was hoisted back aboard Banjo. 

River Test

Last week, Gary and I performed a river test for the engine.  We hauled the boat prior to the test to verify the bottom repairs from last year.  Fortunately, her bottom looked amazing!  Our decision to use the Bluewater Copper Pro SCX bottom paint was a good one.  We did not have a single barnacle, nor bottom growth.  Only mud which washed off easily with a pressure washer.  The “pits” we fixed last year appeared not to have returned.  And finally, the prop speed applied to the propeller had prevented any growth on our prop.

Taking Banjo out for the first time in nine months, she roared to life and motored under her own power with ease.  Her ride was smooth, with the same gentle motion underway.  Gary ran a multitude of tests and checked the system against the engine spec.  All was well.

Final Assembly and Upgrades

Since we were starting from scratch, we decided to go ahead and take care of a few other items with the engine out.  We did the following:

  1. Service and rebuild the fuel injector pump and fuel injectors at Coastal Diesel Service.
  2. Rebuilt the engine transmission thanks to Hale Marine
  3. Replace the suction-break valve and ensure it meets ABYC height recommendations.
  4. Modify the marine diesel engine wet-exhaust to ensure it has the proper amount of “fall” to aid in water removal.

We also looked at making the following upgrades:

  1. Installed a Balmar External Voltage Regulator to the heavy-duty alternator.
  2. Installed an exhaust riser (the pigs tail) on the heat-exchanger.
  3. Replaced the 2-belt system with a serpentine kit for better tensioning and control of the drive belt system.
  4. We have 2 in-series Racor fuel filters that are going to be changed to use a switch-over valve and convert them to a parallel system.  If one gets clogged, we can immediately switch to the other until we can change the fuel filter.
  5. Installed a new water lock.
  6. Added new engine mounts.


In all, we estimate in excess of $25K once everything is said and done, including the repair, maintenance and upgrades. 


Nearly nine months later, we are waiting and financially drained, but able to see some light at the end of the tunnel.  We have taken some hard knocks but we are NOT giving up.  And we are now intimate and educated with the new marine diesel engine.  It is unlikely we will be cruising anytime soon.  Instead, we will be doing whatever we can to replenish our emaciated savings and cruising kitty.  

  I’ll end for now with some major lessons learned.

  1. Insist on closing the raw-water sea-cock before turning over an marine diesel engine you don’t intend to start.
  2. NEVER over-crank your engine without checking the exhaust hoses for trapped water.  In fact, NEVER over-crank the engine.
  3. If water ever does back-fill the cylinders, get it out ASAP to prevent corrosion from setting in.  Change the oil a few times and then run the engine.  Doing so will evaporate any extra water and go a long way to minimize corrosion.  Then change the oil again, and run the engine some more.  Then change the oil again.  You get the idea.
  4. Know how your engine works.  Become familiar with all sub-systems and how they work.  This is critical!  Your marine diesel engine is a LIFE SUPPORT SYSTEM.  Do not wait till something happens to understand it or try to learn what might be happening.
  5. Seek the best possible resources when you need help.  I know that no one likes to spend money, but make sure the money you do spend is for quality and doesn’t accidentally make things worse.
Main Takeaway

If you lack the knowledge of how your boat engine system operates, take some time to learn! Know how your particular system works PRIOR to allowing ANYONE to do anything on your engine that you do not fully understand.  Failure to do so can be disastrous‚Ķ and expensive.  Mistakes are going to happen.  That is just a part of life.  Sometimes seemingly innocuous decisions can have long-reaching, painful consequences. 

We want to offer a special “Thank You” to Deaton’s Yacht Service, and Craven Automotive Machining for doing such a professional, high-quality job in getting Banjo back together!

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4 Thoughts to “Marine Diesel Engine: Banjo’s Full Story”

  1. Awesome post as usual. I love that you go into such detail. Glad it all worked out for you guys. We are thinking about putting Mavis up for the winter (or maybe part of it) in Oriental or Minnesott Beach… Perhaps our paths will cross again!

    Congrats on having propulsion again. It’s a wonderful feeling… (I know).

    1. Sailor

      We hope our paths do cross again! If you get back in Oriental, let us know!

  2. Captain Dave

    Man what a story!! I still dont understand how water gets sucked into the pistons.. You will have to explain next time I see you.

    Glad your through it all – quite a lot of upgrades – your motor should be set for life!!

  3. Jack

    Great story, hope you don’t mind if I use your site for a series of lectures on boat maintenance and problem solving.

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