As a reminder in his book that started it all Voyaging Under Power Robert Beebe recommended that long range cruising power boats should have some way of getting home should their main engine fail. In Salish Aire's case we have a second very small "wing" engine for emergency use. The engine has its own transmission, prop shaft, and propeller. The original propeller was a Martec brand 2 blade folding propeller that causes minimal drag when it is folded underway but is very weak when backing up.
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| Martec propeller folded |
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| Martec Propeller open |
Max-Props use a gear system so that they have the same torque in reverse as in forward and feather when they are not in use. When we found a used one at a swap event we decided to give it a try. After some rehab work we ended up with a $2000 prop for about $700. I had planned to dive the boat and install the prop until I realized installing it is a VERY complicated process with 24 possible different settings each involving lining up different gears marked by dots and letters. We also found that even with the settings color coded we still found assembly on dry land to be challenging just because everything must be aimed and then slipped together all at once.
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| Max-Prop (feathered for minimal drag) |
After getting a recommendation from a Max-Prop dealer for a setting to try first we decided to take advantage of our planned haul-out in Puerto Penasco to install the "new" prop. We were able to install it after several tries and hoped it worked as the installation involved cutting off about 5/8 inch of our propeller shaft which may make it difficult to impossible if we ever need to go back to the original MarTec propeller.
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| A Max-Prop disassembled - this is what we had to work on underwater (the only parts that stayed put were numbers 1-5 on the diagram). |
Once underway we finally had a chance to try the new installation and it was a dismal failure. The engine didn't like the load and put out ugly unburned black diesel, the boat barely moved with the propeller producing lots of tiny bubbles and little thrust. An email back to the dealer and we had an updated recommendation for how to set the blades. The problem was our emergency engine was not available for emergencies and we don't plan to haul-out for at least another year.
I figured we had about a 20% chance of being able to reset the propeller in ideal conditions in the water so we decided to give it a try. We waited for low tide in an anchorage with very clear water, very little wave action and a smooth sand bottom where we might be able to retrieve a dropped part or tool. We had heard of divers using an umbrella under a work area to catch dropped tools and parts but didn't want to sacrifice an umbrella with metal parts if we didn't need to so we came up with the idea of using Clarice's swim seat as a catch basket. As best we could we anchored the swim seat with dive weights so that the mesh seat was under the work area but in reality it needed to be held in place so it wouldn't move too much. This meant that I did the primary disassembly/re-assembly while Clarice had one hand on our catch basket, her knee on the rudder skeg to steady herself, and one hand to help me keep the propeller parts from falling all over.
I was able to get the propeller disassembled but when I tried to look for the tiny dots and numbers I needed to line up I just couldn't see well enough through my prescription dive mask without a close-up lens (it was also difficult to clear the grease enough to get a good look at the gears). I finally decided to take the propeller onto the boat which meant lifting it into the boat gate from the dive ladder (its fairly heavy and was in parts at this point ready to go six different directions if dropped) and removing my dive gear all while Clarice stayed under the boat keeping track of the catch basket and tools.
On deck I carefully wiped the numbers and dots clean and soon realized that we had misaligned one gear when we installed the propeller out of the water! In any case I carefully color coded everything with metal marking paint after checking and rechecking the manual for the correct (hopefully) new settings. I dropped the propeller back to the bottom in a bucket, re-donned my dive gear and got back to a very tired Clarice to try to do the hard part of the whole job.
Using the color coding we were able to get everything lined up and the screws in place and ready for the final assembly item of inserting 6 very tiny cotter pins with very tired and shriveled fingers. When they were in place we greased the propeller collected our tools and headed back to the surface after about 2 hours underwater.
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| The only "selfie" we could take with our hands full as I am doing the very last action (inserting grease into the gearbox) before picking up and heading to the surface |
So does it work??? YES! So far our experiments have supported that the prop does what we wanted and will work much better than the original.
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