How long will Detroits be supported?

I wouldn't worry about that. My dad is still able to get parts for an old Gray Marine (a 671 before it was made by Detroit Diesel) from the 1940s. You're correct; there are thousands of pleasure and commercial boats running with Detroits, so there will be a demand for parts and service for years to come.

Just had one (12V71TI) completely overhauled ... replaced a couple of camshafts too ... parts and expertise were no problem. Had the main shaft replaced on the twin disc 514 too ... no issues.

I think the big question with these engines is ... whether the price of diesel will go back up to $5.00/gal. Cruising at 24 knots would become very expensive.

As you say, re-powering is very expensive and the replacement could have it's own set of challenges. Not every MAN or CAT out there is trouble free.

I'll consider my next move over the next several years as I run these 12V71TI's and hope the price of fuel doesn't rocket.

If it does, I'll be doing lots of cruising at 10 knots and 25 GPH.

Mike

Your limitation to detroits isn't a set back. Infact, it can even be a benefit. I'd probably choose detroits over any modern MTU for their reliability, their cheap maintainance, and their long lives. As for 12v71's over 12v92's, in reality any detroit will last very long and all are very reliable as long as your maintain it in good condition and you give it use.

If I may jump into your thread with a question: I've been looking at several boats to buy. Some have new generation engines, some old. The boat I like best has 16v92TA engines. It has less than 500 hours since replacement and has been run very conservatively by an owner/captain; that I know to be true. I'm old (60). I've been around boats for 55+ years. I keep reading (recently) that DD two strokes are trash, yet I remember that, for decades, every boat I owned, rode on or knew had them...and they worked just fine. So, has something changed? Do they blow up for no apparent reason these days? I really am confused about this. I realize the fuel usage is higher, but compared to re-engining.....well, I'll be dead before I'd break even.

That's not quite correct, the 6-71 was made by DD, Gray Marine was the company that marinized it and sold it as a marine propulsion unit. IIRC GM got the rights to that engine design series as war spoils from WWI.

Define supported.... Will you be able to buy/repair parts to keep them running and will there be people around to do the repairs? You're looking at decades. There are still Atlas Imperials out there working. The 110 deries Detroits haven't had factory support in a heck of a long time, yet you can still keep them going as well.

Repowering however may not be as expensive as you think. You can buy replacements used engines out of Boats and Harbors at reasonable prices. The bell housings and attachments are SAE standard so most everything should bolt up pretty straight forward as long as you are staying in the same horsepower range. Probably have to make some mounting brackets.

12-71 versus 12-92... Two different animals in two different power catagories, you can't really compare them unless it's a 12-71TA with big injectors vs. a derated 12-92.

If I removed a set of 16-92's for a set of either MTU or CAT's at around 1500-1800 HP each the price of the engines alone is about $300K, plus another say $75K for R&R after all is said and done. Hard to break even at those costs in most any terms, and plus any vessel old enough to have those will be low in resale value to justify new engines. Rebuilding is between $65K and $85K and widely available.

The other issue I would bring up in reply to Bayside Bert regarding the fuel burn: you bought a sportfishing boat to go, I assume, sportfishing. that means running at cruise out to the grounds, trolling for hours, and running back. yes, I burn 500 gallons a day to fish. at $3 or at $5, I still fish. newer engines may burn 100 gallons less a day, although thats a 25% savings and on the high side of savings, but the bottom line here on fishing and owning a boat like you now own, the fuel cost potential savings is really insignificant in the total picture of what you will be spending on an annual basis for everything else.

10 three day weekends fishing is 12,000 gallons at a 25% savings of $1 a gallon is 12 grand. you'll spend 3 times that amount on your boat annually.

pucker up my friend and welcome to the world of owning a classic sportfishing machine!

I paid $210,000 for my Bertram in 2006. spent $65 in the yard before I brought her home. and that was with 2 engines in great shape. a blower, hoses, odds and ends in the engine room, new electronics, bottom job, yada, yada, yada.....

averaged 40k a year since. no complaints, its the cost of owning a boat like this new or 25 years old.

didn't mean to derail this thread. I think there will be parts for some time to come with all the inventory out there. will a repower be worth it? I doubt it. its almost cheaper to buy a newer boat.

If you buy new retail engines, yes. You can find the same engines with 2000hrs or less or even a fresh overhaul on them for 1/4 that price.

Fuel burn not withstanding. The 92 series go a lot less hours between rebuilds compared to the 71' series. I was qouted by a DD authorized dealership to expect 2800-3200 hours from 12v92 DDEC's, and 4500-5000 hours with 12v71TI's.

I would never take an entire yacht apart and spend 3 months retro-fitting engines on a maybe. Why is someone selling perfectly good running engines that have been trouble free, to replace them with something else? I wouldn't do an engine swap on a maybe or used engines. I'd rather rebuild what's in there, or replace with new ones with full warranties.

2 main reasons you find them: The boat was spec built or built on the cheap, and the resultant vessel didn't have the performance required for the job, or they were due for overhaul so the company bought a set of cores, built them up, swapped them out in a day and got the boat back to work. Then they rebuilt the old engines and sell them at a slightly better deal than selling off the cores (or if you are mechanically inclined, you can buy cores and build them up yourself). I would never spend more than 3 months putting in engines either. Maybe 3 weeks.