Engine Part 1 – Water should stay outside, fuel should stay inside.

As promised, here is the first installment of the engine series. Back in Electricity Part 1, I explained how, at the time of purchase, the batteries aboard Milou were trying to light themselves on fire. The other two strikes against the boat at the time of purchase were: the stuffing box was severely corroded and was leaking at an alarming rate; and the hoses supplying diesel fuel to the motor were also leaking badly.

Leaking stuffing box = water entering boat (read: sinking). Leaking fuel hoses = bad diesel smell, pollution (when the bilge pump dumps it in the lake) and, I suppose, a fire hazard as well.

I’m not sure what the previous owners had done (or not done) to her, but when I met Milou she was bleeding diesel while trying to sink and light herself on fire. An unhappy boat to be sure.

Moving forward with Milou, I decided to set some priorities.

Priority number one: Do not catch on fire. (This was primarily addressed early on in the Electricity Series).

Followed closely by

Priority number two: Do not sink. 

Water should stay outside:

There are so many things not right here.

Believe it or not, what you see in this picture kept me from buying the boat–that is,  until Deb made me do it. The picture shows the back of the motor, or more precisely the transmission (the thing painted green). Moving aft from the transmission is a ball of rust called the coupler; this attaches the transmission to the propeller shaft (you are right, it probably should not be so rusty). The propeller shaft is that little piece that is more brown, between the rust and the corroded green silicon bronze of the stuffing box. Yes, the prop shaft is made of stainless steel and should be a shiny silver metal color. The job of the stuffing box (the corroded light green thing with 2 bolts pointing toward the ball of rust) is to let the prop shaft spin but not let in too much water, ideally a drop or two a minute, when the shaft is spinning. It requires some maintenance. The bolts have to be tightened as the packing material (this used to be oiled flax, but is now Gore-Tex) wears. If the engine is not properly aligned the shaft will “egg” out the packing, making it leak more. Moving aft, it is nice to see that the hose which attaches the stern tube to the stuffing box is double hose-clamped at both ends. Of course, the aft-most hose clamps were so corroded that they snapped as I tried to loosen them; and in the forward-most clamp, the screw was made of inferior “stainless steel” and was rusted away to almost nothing. The thing in this picture keeping the boat from sinking (more quickly, it was leaking pretty good at the time of inspection) is the fact that the 30-year-old hose had shrunk and stuck to both the stern tube and the stuffing box. The hose itself was about 1/8 of an inch thick, and when I pushed hard with my finger, it delaminated and tore. I waited to try that until the Milou was out of the water, because I didn’t want to be stuck like the little dutch boy.

Much better. This picture is from three days ago. The new rust on the coupler bolts is from water that is coming in from a leaking lazarette. Yep, I need to seal that up – don’t worry, it’s on a list.

When I pulled all of this apart to replace the hose (the one that I put a hole in with my finger), one of the threaded studs used to adjust the stuffing box was so corroded that it could not be removed intact. Believe it or not, finding a metric threaded stud made of silicon bronze is not easy. Our friend Kyle has a PhD in metal and has a small metal lathe in his basement. He let me borrow both the lathe and his brain as he walked me though how exactly to fabricate the needed part from a piece of stock silicon bronze. Yes, it was easier to machine the part from scratch than to find and purchase one on the world wide web.

The above picture is after I rebuilt and cleaned up stuffing box; installed new PTFE stuffing; wire-brushed and painted the coupler; installed new heavy duty (3/4″ thick vs. the old 1/8″) Buck Algonquin stuffing box hose, plus four new high-quality stainless steel hose clamps. Now the boat was no longer sinking–or to be precise, not sinking as quickly. As my friend Roy likes to say, “All boats are sinking, just some faster then others.”

Fuel should stay inside:

When we bought the boat, the 30-year-old stainless steel braided hose that led from the fuel tank to the secondary fuel filter was leaking at an alarming rate . I estimate it leaked about one to two gallons an hour. Amazingly, the previous owners did not notice that their fuel use had tripled; nor that, when the bilge pumped kicked on after every half hour of engine run time, there was a rainbow sheen of diesel on water. To be fair, considering the water leak (remember the sinking!) the pump was probably running nearly constantly, and the diesel may have been very diluted. The easiest way for me to fix the leaking diesel would be to simply replace the hose.

I did not do that.

Fuel Diagram
I have lots of little diagrams like this in my Big Book of Lists.

The leaking hose led to a CAV filter, which doesn’t really have a filter medium in it. The CAV sets up a spinning whirlpool of diesel fuel which throws water and heavier-than-diesel gunk out to the walls of the bowl, where it slides down to the bottom and waits to be drained out. The problems with the CAV are first, that it is not see-through, so you have no idea when it is totally full and about to send the bad stuff (water, algae, junk) into the motor; and second, the lack of an actual paper filter. If it had a filter, the filter would plug up before the bad stuff got to the motor. This would stop the motor (no fuel), but at least I wouldn’t have to tear down and rebuild the entire fuel system. Well, the CAV doesn’t have a filter, but there is a filter the motor itself–the so-called primary filter; it is there to save you when the CAV gets overwhelmed.

Looking forward (I am straddling the coupler), Wix primary filter and Racor secondary filter with see through bowl.
Looking forward (I am straddling the coupler), WIX is the primary filter and Racor, secondary filter, is the white cylinder with the see-through bowl full of red diesel fuel.

I have this idea/fear that just when we need the motor most, a big chunk of goober will clog the primary filter, and we will be stalled until we can find a calm place to stop and change the filter and bleed the air out of the fuel system.

I bought a very beefy Racor (500 turbine) fuel filter that has a paper element plus the whirlpool system plus a see-through bowl. So, fuel-wise, I can see when things are getting bad. But still, if the big goober hit the Racor we would be in the same situation; so I plumbed in a three-way valve and a shut-off valve behind the Racor. With the three-way valve, if the big filter gets clogged and we have to have the motor, I can simply turn the valve and the fuel will route through the CAV (now a backup), which may give us the time we need to get out of a tricky situation.


Filter selection three-way valve. Grey thang at he bottom is the CAV filter.
Filter selection three-way valve. Grey thing at he bottom is the CAV filter.

The fuel supply system is now in place and working well. The process from my initial idea (the little sketch) to final working install took about six separate trips up north and a ton of hours. On paper the idea was great, but when I had to put it together in the allotted space, adjustments had to be made. Once I finally got the whole thing working and was testing the valve bypass system, for some reason I was still smelling freshly spilled diesel. After a little investigation, I discovered a leaking fuel return line.

This time, I decided to just replace the hose.

Next up in Engine part 2: Winterizing Mistakes and Converting to Closed Cooling.

One Comment on “Engine Part 1 – Water should stay outside, fuel should stay inside.

  1. I purchased an 83 First 38 in April. Three weeks ago the boat actually started sinking after tying up in the marina. The water was starting to go over the cabin soles!!! I frantically started checking all seacocks starting forward, and when I checked the aft head I heard water gushing inside the boat in the engine compartment. I could not believe my eyes when I saw that the hose around the prop shaft had come off the stern post. I managed to hand tighten it back on the post and stop the sinking before the water reached the engine.
    I wish I had seen your blog earlier.
    The boat is OK, and this was no more than a scare and a lesson learned.
    Thank you for the write-up.

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