Preparation: Removing our Perkins Boat Engine

Removing our Perkins Boat Engine

Today was a busy day.  This morning, we received a knock on the hull and found Gary, one of the Deaton’s Yacht Service employees, requesting to come aboard. We welcomed him and took a couple minutes to listen to his plan for removing our Perkins boat engine. We decided to remove the engine due to finding sea water on top of the pistons and water in our engine oil.  Early in our discussions with the boatyard, I expressed an interest in learning as much as possible about the engine. Gary remembered this and gave me a list of items I could do.  This would also serve to give me experience in preparation for removing our Perkins boat engine and also help reduce some of the labor costs.  The plan was to try to pull the engine today, which later changed to removing the engine tomorrow. 

Removing our Perkins Boat Engine Removing our Perkins boat engine

Deaton’s was just as worried about our engine as we were.  They were eager to get the engine pulled and the head off, so an assessment could be performed.

Tasks for Removing our Perkins Boat Engine

Our preparation tasks for removing our Perkins boat engine were to disassemble the following from the Perkins 4.236 Marine Engine Block:

  • Exhaust manifold
  • Engine alternator
  • Mounting bolts that hold the engine to the hull
  • External oil filter plate and filter
  • Decouple the transmission from the propeller shaft
  • Any additional disassembly to allow the engine to be completely detached

I jumped at the chance to do some work, and Shannon and I took a few minutes to get all of our cameras ready for filming.  Our desire to film the work was two-fold.  First, we would have a record of where everything connected to the engine for later reference.  Second, we could share what we learned.  Gary would be responsible for taking care of the fuel system, sliding the prop shaft away from the transmission, and the transmission linkage.

Engine Alternator

The engine alternator project was tackled first in preparing for removing our Perkins boat engine.  Banjo’s alternator is located on the starboard side of the front of the engine on an external mounting plate.  The alternator is also attached to a rocker arm bolted directly to the engine.  This arm allows the alternator to be moved and apply tension to the drive belts.  All of the bolts were removed and a light tap with a rubber mallet relieved the tension to the belts.  I left a couple bolts in place until I had the power disconnected.Perkins 4.236 Marine Engine Alternator

My Bonehead Move of the Day

Like a complete dumb ass, I did not turn off the main battery bank before disconnecting the red (hot) power wire to the alternator.  I did think about it briefly before putting the socket on the nut, but decided to just be really careful in case the cable was still hot.  That was SUCH a stupid move.  It was hot!  I accidentally touched the socket wrench to the crankcase and received with a loud pop and a bright flash.  We checked the fuses and found we blew the bus bar fuse for that circuit.

Turn off the power dumbassDumb.  Dumb,  Dumb!  And I knew better, but I ignored my inner voice telling me to slow down.  In a rush to get the project completed, I ignored my own rule for electrical safety.  For the next 15 minutes, I chastised myself heavily and thanked the heavens I wasn’t hurt.  Afterward, I promised that I would NEVER, EVER touch another circuit without checking it first with a multi-meter and making sure the power was OFF.

Once the power was disconnected, I wrapped all of the terminals with electrical tape and secured them out of the way.  The final bolts were removed and the alternator and mounting plate were removed.

External Oil Filter

The next project to tackle in preparing for removing our Perkins boat engine was to remove the oil filter mounting plate, the oil filter and the engine cooler hoses.  Our friend Harrison had previously removed the engine oil cooler to help rule it out as the cause of the water in the engine.  We had the cooler tested at Deaton’s and no leak was found.  So we left that portion of the engine disassembled.  This is what the Perkins 4.236 Marine Engine Oil Cooler looks like.

Perkins 4.236 Marine Engine Oil Cooler

Since the cooler was already off, the oil filter, located on the starboard aft side of the engine below the exhaust hoses, was easy to access.  Our mounting plate used four bolts to attach the filter to the crankcase.  Since there might still be oil in the filter, we were careful to place oil absorbent pads, which we call “diapers,” on the floor of the engine room.  The filter was unscrewed and we moved it immediately into a bucket. 

Removing our Perkins Boat engine Removin g our Perkins boat engine

The system did still have some oil inside and all of the oil was caught by either the bucket or the diapers.  I handed the assembly to Shannon and that completed the disassembly.  Deaton’s has a used oil reclamation station, so we removed the rest of the oil and disposed of it properly.

Exhaust Manifold

The most time consuming portion of the preparation for removing our Perkins boat engine came from the exhaust manifold.  Our manifold is mounted on the far right top of the engine.  It contains a heat exchanger, which circulates raw water around the coolant to remove heat.  It is the boat equivalent of an automotive radiator, except it works with sea water.  The raw water then moves through an anti-siphon valve before mixing with the exhaust gases and pushed out of the boat.  The best theory, so far, is that our anti-siphon valve failed due to its placement in the boat and/or the device itself being worn out. 

Perkins 4.236 Marine Engine Exhaust Manifold

Coolant Removal

Our first step was to remove the existing coolant from the system.  This is an important step when preparing for removing our Perkins boat engine.  Aside from helping to lighten the weight of the engine, it also ensures all chemicals are handled properly.  It is important to avoid spilling harmful chemicals.  Located on the port side aft of the engine is a small 3/8-inch plug that is removed to drain the coolant.  I was doing more boat yoga in the compartment.  We used a funnel at first to drain the coolant into a small bucket.  I would then stop the hole with my thumb and pass the bucket to Shannon.  She would empty my bucket into a 5-gallon bucket to be removed later.  

Due to the space constraints, and my inability to master that particular boat yoga pose, I ended up getting stuck holding the bucket with the wrong hand.  That made it impossible to remove my thumb to pass the bucket to Shannon.  Shannon rushed to the rescue with a portable hand siphon pump she found and began sucking the coolant right out of my bucket.


When we first tried this approach, there was a small accident where some coolant spilled back down onto me and on Shannon.  Luckily, my shirt absorbed every drop.  I enjoyed my new polyethelene-glycol cologne for the next couple hours.

Delivery Pipe

In order to get the coolant into the engine, Banjo has a delivery pipe that connects the exhaust manifold to the engine block.  The ends of the pipe attach with rubber hoses and hose clamps.  All of these hoses and clamps will be replaced with fresh ones.Perkins 4.236 Marine Engine Coolant Pipe and mounting rail

The Manifold

Our exhaust manifold is mounted on a rail for support and then uses four bolts to directly mount it to the Perkins 4.236 Engine Block.  The most difficult aspect of the removal were the inside block bolts.  The manifold has a cut-away area around the bolts, but there isn’t enough room to get the socket wrench in there.  Although three of the bolts were fairly easy to remove, the fourth took over an hour.  It was due to this final bolt I made the decision to remove the air intake.

Perkins 4.236 Marine Engine Systems

 I removed the intake and exhaust couplings, which were simply rubber hoses.  We saw more raw water spill into the bilge when the exhaust couplings were removed.  Once completely detached, the manifold lifted right out of the engine room.

Perkins 4.236 Marine Engine Exhaust Manifold Perkins 4.236 Marine Engine Exhaust Manifold

Mounting Bolts

The mounting bolts were actually my favorite part of the day.  Most likely due to their ease of removal.  Our engine mounts are showing signs of age and wear, and will likely be replaced.  The removal, however, was actually quite easy.  Using an impact wrench on low-power, and a 3/4-inch socket, the lag bolts which hold our engine to the hull, came out with minimal effort.

Perkins 4.236 Marine Engine Mounts and mounting bolts

Engine Air Intake

Originally, we hadn’t planned to remove our Perkins 4.236 Marine Engine air intake.  We have plenty of clearance to leave it attached.  However, as mentioned in the exhaust manifold section, I found I could not get the fourth bolt free without removal.  The air intake sits between the crankcase and the exhaust manifold.  There is a 2-3-inch gap between each.  The air intake was held in place by 6- 14mm hex-head bolts screwed directly into the engine block.Perkins 4.236 Marine Engine Air Intake

This was the second easiest removal of the day.  The hardest part was getting the socket into the small space to reach the head of the bolts.  Once we figured out the boat yoga necessary, the air intake came apart easily.  I made sure, as with the rest of the bolts, to put them back in their holes.  Also, I took care to put the gaskets back in place for reference later.

Decouple Transmission

Our propeller shaft enters the engine room just slightly ahead of our skeg and rudder.  From there, it passes through a stuffing box, which keeps water outside the boat.  Next it attaches to a coupling which mates with the boat’s transmission.  Although I had planned to complete it today, I ran out of time and energy.  Therefore I decided to get up early tomorrow.  There are 4 bolts that hold the transmission coupling to the shaft and those need to be removed.

Perkins 4.236 Marine Engine transmission  Perkins 4.236 Marine Engine transmission

Additional disassembly

Banjo has a hot water tank that is either powered by shore/generator AC power, or the heat from the engine.  She accomplishes this by circulating hot engine coolant through the water heater, which uses the heat to provide hot water.   The two hoses that run from the engine to the heater were removed.

Also, there were a few more electrical connections on the port-side of the engine needing detachment.  There were for things like the fuel injector pump, temperature sensors, and other sensors.

Perkins 4.236 Marine Engine Block Perkins 4.236 Marine Engine Block flywheel and right side
Perkins 4.236 Marine Engine Block Starter and oil filter mount Perkins 4.236 Marine Engine Block Air Intake

Next Steps

So if the plan remains the same, Gary will be removing the engine tomorrow.  Unfortunately, due to liability, we will not be able to be onboard when the engine is lifted.  We will, however, be standing close-by so we can shoot video and take pictures to share with you.

Once the engine is safely in the boatyard machine room, we will begin the process of tearing it down.  the first step will be to perform a full assessment of the state of the motor.  Then we will make a decision on how to proceed.  Fingers crossed we can rebuild and repair instead of having to replace.

Be sure to follow the rest of our removing our Perkins boat engine saga as it continues.  And check out more of our boat maintenance and repair projects.  We will be posting a full video from this experience on our YouTube Channel in the coming days.  Don’t forget to subscribe early to receive notices of updates!

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2 Thoughts to “Preparation: Removing our Perkins Boat Engine”

  1. Hannah

    Deaton’s replaced our 4-236 as well. We coukdn’t Be more pleased. Tell them Rita T says hi.

    1. Sailor

      We will tell them!! Fair winds and be safe out there!

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