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After a LOT of searching, cross referencing and double checking, I found that the Universal M3-20 block (D-640) was the same engine block as what was sold as a Kubota G-6200 lawn mower. That was the breakthru information that changed the scope of my searching and once I started watching for those parts, the options opened up one day when this part and several others from a G-6200 mower were being sold. I also picked up a oil pan (with no rust or corrosion) and an oil gear pump that turns like new - and I still had a good deal of change from a “$20.00 bill”- patience may be a lot of things but in this case, it was one of the primary factors that made the rebuild for this engine possible. In the photo above, the red arrow is pointing to the area that has to be bored out to accept the water pump at the specific location to align with the slotted shaft on the engine that drives the pump - shown in the photo below. The case not only protects the internal gears but permits specific oil paths and coolant paths to be connected. It was a relief to see that no rust or contamination had reached the inside areas and with some care in boring, the alignment with the newer case housing would permit everything else to remain as it was originally built. |
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There was no hour meter on the boat when it was purchased so there’s really no way to know exactly how many hours were on this engine. My “best guess” is based on the age of the boat and when these Universal M3-20 engines were introduced to the market. They were available sometime around 1988 and on into 1992 before being replaced by the M3-20B version with slightly more horsepower. I’ve assumed that the engine was replaced (for what reason - we’ll never know) in 1990 and that given the overall installation quality and attention to details, I don’t believe it was used that much. I bought the boat in 2000 which leaves 10 years at 40 to 50 hours per year (if that) for an estimate of 400 to 500 hours on the engine. From the visual condition of the engine alone, that seems like a high number but there are multiple clues that also go into making that guess. The exhaust elbow (with water injection) was not that badly worn or corroded and appears to be the original for this engine. In warmer climates, salt water takes a heavier toll on almost all metals and things don’t deteriorate as quickly if they’re just sitting in the water as opposed to being used. Other areas like the air cleaner / filter - looked to be original (again not likely after 10 years if it was used much at all.) The heat exchanger still has a reasonable flow thru and I would bet serious money on no one replacing the zinc electrodes on that item - so it appears to me that from a “best guess” scenario, putting this engine back in the boat after replacing several items prone to wear and corrosion (raw water pump, fresh water pump, hoses, heat exchanger, thermostat, alternator, etc.) I should be able to get another 1k or 2k hours out of it without major issues. One additional issue that supports this approach was the engine oil analysis that I had done just after pulling the engine - it showed no significant chemistry items that would suggest further problems based on past use. Had that not been the case, I would have more likely opted to replace the entire engine with either a new or used alternative - in either case at a much higher cost than the bills for the restoration being done now. |
There’s still a lot of work to be done in getting everything re-assembled and checked out before re-installing the engine back in the boat. I’ll add in some additional photos along the way to show the progress. Not all engine manufacturers have “alternate” opportunities with “marinized” versions, but one of the options I had considered IF the choice was to buy a new engine was the BETA BD722 - you can do the homework on them and find they too, promote the option of not having to buy parts from your local marine sources at inflated prices. They too, use a Kobuta block in their engines and I tend to think that when someone does something right and does it enough times, the results are probably better than average. That doesn’t mean there won’t be some surprises, but they should be fewer and “further between” than others. BTW.... I found a new set of (4) motor mounts (the same as the ones sold with the Beta engines) on Ebay and ended up getting them for less than half the price of a new set. It really does “pay” to be patient and persistent in your searches! |
Finding a replacement alternator was the goal but finding one that would fit with the clearance needed was the problem. Of all the searching and checking to find some items, this detail probably took the most time simply because not all vendors provide accurate or even legible pdf drawings and the amount of “third party” aftermarket items almost overshadows the real companies selling real products. After all the checking, it was satisfying to get a good result for this issue. |
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