Advice needed on potential purchase. Engine decision?

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By the way, when I say I'd only buy the boat assuming a full rebuild on both engines, that doesn't necessarily mean the seller would have to drop the price by the cost of the rebuilds, nor does it mean you need to go do the rebuilds right away.

You could accept any combination of a lower purchase price, a prediction of a large future expense, and risk. It's really a risk-adjusted future expense. If I bought the boat, I would at least consider doing what a number of people have suggested which is just change the oil in the engines and gear, run the boat, and monitor. Maybe the boat would work fine, or work fine for some amount of time. But it might also turn out like the buy who bought the boat in St Louis and only made it across the river before his engine crapped out. This is the risk part. If you "win the bet" you could end up with a discounted boat that works just fine after a few oil changes. Or you could lose the bet and end up with a boat discounted by $10K, but facing a $50k rebuild (or whatever the numbers work out to)

Did we ever establish whether these are 671s vs 8V71? Wasn't that significant with respect to the power rating?

And I'm having trouble getting my head around engines that needed rebuilds at 3000 hrs, but I gather that's not uncommon with the DD 2 strokes? I guess it's not that they last forever, but that you can keep rebuilding them forever.
 
twistedtree said:
And I'm having trouble getting my head around engines that needed rebuilds at 3000 hrs, but I gather that's not uncommon with the DD 2 strokes? I guess it's not that they last forever, but that you can keep rebuilding them forever.
Click to expand...
They're often rebuildable forever. And in their lower HP ratings or when not run too hard, they last a long time as well. The basic design just didn't hold up as well when they turned the power way up, particularly when people ran them hard. They don't tend to fail catastrophically, just wear out faster the harder they're pushed.
 
I received estimates yesterday for overhauling one 8V71 engine… the detroit folks in-frame: $71K.. an experienced independent detroit mechanic: $40K per engine. If the 2 of us do some work and help the independent mechanic such as taking off parts ahead of time, moving things, cleaning, running errands, ordering stuff, essentially working side by side… I am not sure how much reduction in labor $ would result. At the very least the project would be completed in less time. We would be carrying out the prep, cleaning and helping out regardless of the situation.
 
Well, the deed is done.. $12k discount essentially. I had several conversation with different experienced folks and felt comfortable enough. Also, I identified 2 independent mechanics that do overhauls through recommendations where cost would be more reasonable if things go south.

Thank you again to everyone for the input.
 
Our Euclid dozer (1964) sits at 6500’ elevation on a mountain top every winter and fires right up every spring…a lot of white smoke (unburned diesel) until all injectors start firing, then engine smooths right out. A bit of hard work and the engine burns nice and clean…has been this way since our ownership in 2012.

The 6-71 is a bit tired and prefers a block heater but is near impossible to kill! Chances are you may run those Detroits a fair while as is.

Good luck on your new boat!
 
Get a service manual. Usually some on ebay. Learn your engine as it's being overhauled. Then later you can do the maintenance and maybe some repairs and reduce the cost of boating.
Detroit 2 cycles are not that difficult to understand. The design basics go back to the 1920. But 2 cycles are different than other diesels because of the injector system. And marine mechanics can't seem to learn the difference.
If you do want to learn your engine find a WWII school manual. It will be about an inline 6 cylinder but everything is the same. The sleeves, pistons, rods are all the same. It breaks down every part and system down.
 
Lepke said:
Get a service manual. Usually some on ebay. Learn your engine as it's being overhauled. Then later you can do the maintenance and maybe some repairs and reduce the cost of boating.
Detroit 2 cycles are not that difficult to understand. The design basics go back to the 1920. But 2 cycles are different than other diesels because of the injector system. And marine mechanics can't seem to learn the difference.
If you do want to learn your engine find a WWII school manual. It will be about an inline 6 cylinder but everything is the same. The sleeves, pistons, rods are all the same. It breaks down every part and system down.
Click to expand...
What's unique about the injector system, especially as compared to other unit injector systems? I have limited knowledge about the DD 2 strokes.
 
I have not seen the inside of a cyclinder for many years. I saw the post of rust inside after two months and did not see any major concerns expressed. So is it normal to have rust inside cylinders in just two months?
If yes then every boat laid up over a winter has rust inside.

IMO if an engine does not start within 3 revolutions there is a problem.
 
I am definitely working at getting all manuals. Boatdiesel would have been a great first resource.. I found a potential source online?? Will see how it turns out. I am going to fix the oil leaks, change the oil & coolant, clean the airsepts, change the racor and run the engines for a few weeks to see how they feel.

Here is something that I had not seen before. In the oil analysis from Blackstone, they had the conc of iron in the oil, which was elevated at 109, next to it was a local average of iron (110) for the region and a universal average of 20. The region being south florida.

Thanks for eveyone’s input

Raylee
 
mvweebles said:
Iron and copper are both wear metals that can presage failure. Copper especially is a marker for lower end bearing failure as @tiltrider1 suggests and has nothing to do with sitting in a salt water environment for any amount of time (2-months is a lame excuse, BTW).

There was a recent thread about a Hatt 58 that was recently purchased and headed to Tampa from the Mississippi area (I forget exactly). One engine was a bit slower to start than the other one but the buyer proceeded with the purchase. The engine self-destructed a dozen engine hours later. Since the owner was on his way to Tampa, I can only assume he thought the engine was good enough - I wouldn't be surprised if he was given a dismissive explanation along the lines of "run it for a few hours to re-set the rings." Talk is cheap when you don't have skin in the game.

Attached is a very good article from Steve D'Antonio on interpreting oil analysis.

Good luck. Please update on your progress.

Peter
Click to expand...
I bought a used 58 Hat MY some years ago. Powered with 8v-92's rated at 550 hp with 600-odd hours. I blew an engine at 900 plus hours. Replaced it with a new 8-92 rated at 735 hp. That one blew at 800-odd hours, I had the opportunity to speak with one of the top engineers at Detroit Diesel. He asked what rpm I ran at. When I had a long ways to go like from my homeport in CT to Fl. I ran at the top-recommended cruise rpm of 2100. That was my problem I was told. Ideally, the top rpm is 1,600. Commercial tow boat operators I interviewed said that that 1,600 or less was the rpm. Also their engines had smaller injectors and less boost. I sold the boat. RIP.
 
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