Sunday, December 14, 2014

43 milimeters

Again, like on the previous post, I must warn you about the technical aspects of this post.  Many might find it boring beyond belief.

Perkins 4-108, victim of ineptitude
In the sweltering heat of June in Guaymas we considered our options for a re-power. The Perkins diesel was dead, its crankshaft cracked.  Omar had removed it from the boat and we had a huge gaping hole under the galley floorboards.  What kind of engine should we buy?  The Yanmar brand is a reliable choice with a good support network in Mexico and the states.  We could purchase one new for about 12k USD.  We knew two fellow boaters who had re-powered with a Beta for less money so I looked into that option. The Beta company takes the reliable Kubota diesel engine from Japan and makes the necessary changes to it for installation in a boat.  Ordering it directly from Beta in Gloucester UK would save us a thousand dollars over a U.S. distributor so I took that route.  9k later we had struck a deal.

Pretty on the outside, flawed on the inside
Andrew Growcoot, the company CEO, sent me a measuring template and I set about measuring the motor mounts and prop shaft location.  From my boat documentation I found the transmission identified as a Hurth HBW360.  I PRESUMED that when Rafael replaced the transmission he replaced it with the same model so that’s the model transmission I told Beta to use to determine if the engine would fit and to design the custom motor mounts. Andrew assured me that the HBW360 would be a good match for the Beta 43.  I now know that Rafael used a ZF10M transmission because they don’t make the HBW360 anymore. Three months later when Omar lowered the new engine into the bilge and started taking measurements he found that the engine did not fit properly and the motor mounts were a couple of inches off.  In addition, the dampener plate had a 32 tooth spline instead of the 9 tooth spline and would not fit. 

Just like I learned back in my computer programming years, if garbage goes in then garbage comes out.
Simple measurements, right?

I also knew we had some issues with the forward port side motor mount.  There was some rust under the mount and it had come loose when we started having engine problems.  Omar had the yard fiberglass man, Francisco, dig into the stringers under the engine to chase out the rust.  Just under the fiberglass long steel plates were embedded into the stringers.  On careful inspection, not only had the forward port side plates rusted but all four mount locations were compromised.  Francisco spent many costly hours digging out the rusty iron.  He dug down all the way into the wood stringer until he was at a solid and dry surface.  Then be built it back up with a stainless steel plate and multiple layers of fiberglass.  Omar’s measurements showed that the stringers were too high anyway so the result was that the engine could sit a little bit lower than before.

The custom feet I ordered worked for the front two motor mounts but the rears came nowhere close to fitting.  Omar tossed those and had two more custom made at the local machine shop.  The rear bell housing on the engine was too wide to fit between the stringers so Omar removed it from the engine and had the machine shop shave off a half inch in width. Finally the engine was on its mounts and everything lined up as it should.  Why were there so many problems?  Why? Because I told Beta the wrong Transmission!  Garbage in, garbage out.
HBW360 with 105mm
The old HBW360 had a drop of 105mm between the crankshaft and the prop shaft.  The ZF10M has a 62mm drop.  The difference of 43mm threw off all the calculations for the custom feet as Andrew figured the engine was sitting higher up above the mounts than it really was.

Once I figured out that I had a different transmission I shared that knowledge with Andrew at Beta and his reply was, “You need a bigger transmission.”  What!  How could it be that the Perkins 4-108, rated at 50 HP was fine with the transmission but the new Beta at 43 HP needed a more robust unit?  Here is the reply from Beta:
ZF10M with 62mm

The Perkins 4.108 developed 50 HP at 4,000 RPM and at 2,800 only developed 36 HP.

The Beta 43 develops 43 HP at 2,800.  

The Perkins developed 75 ft lbs of torque at 2,200 whereas the Beta 43 develops 95 ft lbs of torque at between 1,600 and 2,000 RPM.

The Perkins is 108 whereas the Beta 43 is 122

Experience has shown that the ZF10M cannot handle the torque of the Beta 43 for very long.

Well, there you have it. The good news is that the new Beta will have quite a bit more pep than the old Perkins.  The bad news is that my assumption about my transmission caused a cascading set of events that cost quite a bit of time, materials, and dollars.  Granted, if I’d reported the correct transmission, the Beta guys would have insisted that I order a different transmission from the get go.  But poor Omar… had to deal with an engine that wouldn’t fit, rusty mounts, and dumb old me.

If you, like me, are wondering what torque vs horsepower means, then join the club.  Being a tech guy, I googled it.  One horsepower is how much umph one horse can pull, or push.  Can that stallion pull that wagon up the hill or not?  On a boat, having horsepower is good but having a lot of torque is even better.  Once the  horsepower gets the boat to speed it’s the torque that keeps it there.  My old Newport 27 didn’t have much torque.  When you slammed into a big wave the engine would slow down and take a little while to get the boat back up to speed.  With more torque, the engine would keep on trucking at the same RPM.  Our new Beta should be able to bash into a heavy sea with more staying power than the old Perkins. She’s got more torque, more guts! Clear as mud now?

We ordered a beefier transmission, delivered to Phoenix.  Connie and I drove the Dolphin back up to the states, sold the Dolphin for some much needed cash, then took the Tufesa bus back down to Guaymas, carrying a new ZF15M tranny along as baggage.

Back in the yard life had gone on as before.  A few boats came into the yard and many more had left.  The weather was exceptional and the yard was a beehive of activity as boaters scrambled to finish up their projects so they could “splash” their boats and sail south.  It’s a very social time in the yard with everyone visiting and discussing the various fixes going on.  Transmission replacements, keel work, welding, cutlass bearing replacements, painting, fiber glassing, all sorts of work was happening.  Doug has a great way of putting it, “The great thing about this yard is that you can always find someone who has a worse problem than you have.”

Snug in the bowels of the bilge

We are in the last throws of our repairs now.  Omar will finish the engine alignment maybe tomorrow and we’ll see what he thinks our solution should be for a rudder stop.  After that, we should be ready to launch.  Meanwhile, Connie and I are ticking off our to-do list of little things that are much easier done out of the water than in the water.

And hey, if you are here in the boatyard, drop on by later this afternoon and we'll have cocktails while we tell each other horror stories about repairs gone rogue and projects that developed a life of their own.


  1. I like the part about the cocktails in the boat yard! Would love to join you for that!

  2. You earned a few on us with this story, find a fresh infusion to your cruising kitty! Hope someone is using that 'ol perkins as an anchor somewhere, the "Gonher" fuel filter in the photo was telling!