Mercruiser Alpha One have been in production for (guess) 35 years. They are a great outdrive. Obviously the newer outdrives with duo props are better as is having the raw water pump run off the engine rather than the outdrive.
I could buy an entire aftermarket Alpha One outdrive for less than the cost of one gearset for my VP outdrive.
I dont know if the duo props are better. I am a fan of the Alpha One, been boating for decades, never had one fail, shift clunk and all, they were awesome and trouble free. I serviced all my Merc outdrives, pulled them every year, greased the splines, simple and maybe a bit "crude" but are work horses. (im typing this for a reason)
Fast forward to the year 2018. Kids grown just the wife and I now, have other toys like the Road King, Purchased a new to us 2008 Chaparral 180SSI to use on the lake. Easy to take care of, perfect boat to take out a few hours on the weekend. The boat was in like new condition, get this, had 65 hours on it.
It has a Volvo SX-A outdrive, First year I was in awe. whisper quiet shifting, NO clunk, engine mounted raw water pick up, wow, how cool.
Runs like a champ ... and then, one year later .... we started to get a delay when shifting into forward, not every time but when it did, slowly but surely it would go into gear. End of the summer of 2020 it was getting worse, IN 2021 it would no longer go into gear, always reverse but not forward. Cone clutch was shot at 100 hours, I read on some forums of this issue back in, ready? Model year 2008 which is the year this updated SX-A outdrive came out. At 100 hours, some units developed this issue.
Anyway, first time in my life, which is decades and decades, in boats from 17 feet to 27 foot Sea Rays I always had Merc outdrives never had an issue and the first time in my life have a Volvo outdrive being worked on at an enormous cost. Hopefully this will be the only issue, we should have the boat back in about 7 business days more. We gave the go ahead to order a new OEM factory SX-A upper gearcase. Costing us almost $5000. If there are no more issues with it, we are ok because the boat is still in showroom condition, engine doesnt use oil and doesnt even have a rusted bolt on it.
...and that "on engine" sea water pump ... well I decided to have it replaced and it isnt cheap, new housing and all.
It will al be worth it, IF this is the end of unpleasant surprises.
... oh and by the way ... no one in this area wants to work on these outdrives, even though its current ... limited experience and why I had to get a new upper gearcase from a volvo authorized dealer. Another thing, first question you are asked at most places is how old is the boat, over 10 years they will not work on.
