Which Diesel Is Easier To Maintain?

Between a Cat 3208 and a Detroit 6-71 which diesel is the better choice in a 30 year old boat?

A few more details please. Start with vessel, HP/Model and then go from there.

This is not a good comparison. Both engines came in different HP configurations. If I needed 375 hp I would pick the 3208. If I only needed 220 hp I would pick the 671. If noise is an issue I would pick the 3208. If I needed a 20,000 hour engine I would pick the 671.

This tit for tat argument could go on for ever between these two engines. Maintenance cost between these two engines is going to come down to luck.

What kind of access do you have to the engine(s)

“Easier to maintain”

There we go again. Putting getting out of work at the top of the list.

ktdtx said:

What kind of access do you have to the engine(s)

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Good point.

Easier access means easier maintenance.

Easier may be mostly re how easy it is to obtain parts.
DD would get the nod then.

6' 5" headroom and walk around engine.

menzies said:

6' 5" headroom and walk around engine.

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OK, now you are just rubbing it in...

I have 3208 naturals 210 hp. I’m not going to wear them out, so hours are irrelevant. As already said lifespan won’t be hours based and will come down to luck and what decides to break. 3208 is fewer moving pieces, simple, and very easy to maintain. I had a head off this winter, simple business. A Detroit is a more complex beast, but if I did have to do a rebuild, I’d rather have a Detroit. More infinitely rebuildable, especially in place. That’s where the cat would fall down. Cat or Detroit parts are plentiful and easy to get. I can order anything online and have it ready to pick up or shipped to me before Friday.

I wouldn’t kick either out of bed for eating crackers.

I think Detroit’s are easier too because you never have to change the oil, just wipe underneath daily and add a little more oil. Never owned one, just admired from afar.

Perhaps an engine which has easy top, left-side and right-side access.

Which Diesel Is Easier To Maintain?


Its easier to adjust the valves on a Detroit 6-71 .Cat injector pump's are a bugger to set up. So id say Detroit 6-71

Gotta laugh at some of the comments from the very experienced wise older heads...…….
Ghost quoted - " I think Detroit’s are easier too because you never have to change the oil, just wipe underneath daily and add a little more oil. "
LoL

AusCan said:

Good point.

Easier access means easier maintenance.

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And easier maintenance (in all forms) can be construed as better maintenance all around including clean up.

And some is still personal.... I would rater have complicated maintenance that is easy to get to thsn more simple maintenancd that is a bear to get to.

Like many have posted...they take raw water pumps off (because its easier) and change the impeller on a bench. Probably resulting in a better overall job.

menzies said:

6' 5" headroom and walk around engine.

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Agreed

The 6-71 is by far the simpler and more reliable engine, in my opinion. However, they are noisier and prone to leaking oil. Cat parts are just plain expensive, whereas 6-71 parts are not. The 6-71 is a two stroke diesel with tube fed injectors, so no bleeding necessary when changing filters, whereas the Cat is a four stroke with a more complex fuel system that requires bleeding.

I would probably choose the 6-71 but it really depends on the boat and how you plan to use it.

for a 37' hull, and having been around cats, i would pick a 471, 453, etc, or find a good used 4 cylinder cat...all those engines run forever! get the correct size injectors, for the job! i have a 40' round bottom skookum, have a volvo 70B, with 10,000+ hours, use #30 oil, they could have put a 471/453, smaller, more room in the engine room! 3208's are configured in a way to make them dificult to reach some things...clyde

Pgitug said:

Between a Cat 3208 and a Detroit 6-71 which diesel is the better choice in a 30 year old boat?

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Kitty Cat. We are big Detroit fans but can’t find parts for them anymore.

as as talking to people that have cruised the world, detroit parts also are on tractors, trucks, etc...i still really like the cat straight 6`s, or 4`s...and yes parts for them are available from cat, and they are everywhere...clyde

3208.. Welcome to old tech vs ancient tech.

6-71's belong in a museum.. They paved the way but let them rest.

The 3208, lovely reliable engine, BUT access is everything and that's down to the boat builder.
I'd be more concerned about the engine servicing history, I've seen engines with low hours, many sitting idling in a marine and they were prone to leaks and smoky, Volvo are very prone to leaks if left idling for long periods.
The colour of smoke from an engine gives the first clues, if its a turbo'd engine sometimes nothing more than a good run gently building up the power slowly and then run hard for half an hour will clear it.
Quick test of engine oil, get a drop on your finger, touch it lightly with your tongue, don't be a bloody wimp it wont kill ya, if its acidy its not been serviced lately if its sweet then its fresh and recently changed.
Without seeing it its all just war stories from old fogeys like me but for my money it'd be the CAT.

The 671 doesn't have an injector pump, just a fuel pump that lasts decades. Injector pumps last a long time but when they fail the engine doesn't run, they're hard for some people to bleed, and they're expensive to rebuild. I never lost a Detroit injector in about 55 years of running Detroits. But if I did, the engine would still run. Almost all Cat parts have to come from Cat and are very expensive. You can buy Detroit rebuild kits for all the pumps, blower and other parts from non-Detroit makers. Just as good, but cheaper. Cat makes a good engine, and is more reliable that almost any other yacht engine, but the 671 is more reliable than the Cat.
3208 natural and 671 natural have similar HP, but the Detroit achieves it's max HP 1000 rpm lower. The 3208 is rated continuous at 70% 0f HP. The 671 can run at 100% of max HP just about forever. That's how I run mine.
The 671 is easier and faster to adjust valves and because the injector is activated by a 3rd rocker, it's possible to better balance the cylinders with small changes in the injector clearances.
The 671 was in production for about 60 years so any bugs were worked out many years ago.

I'm familiar with the 2 stroke diesels as I worked in R&D at Rolls Royce where they made a 6 cylinder 2 stroke opposed piston.
In all my years running and working diesels I've never had a pump break, the only trouble I once had was a Scania 500 hp V8 slipped the flexible coupling to the pump and it took 10 mins to get the engine TDC and 5 minutes to fix it, I was in minus 10 degrees in Poland at the time and that fairly concentrated the mind and got me moving to get back in the warm with a mug of steaming Irish tea with a wee nip in (to help the circulation you understand).

menzies said:

6' 5" headroom and walk around engine.

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You left off air conditioned engine room!

Irish Rambler said:

I'm familiar with the 2 stroke diesels as I worked in R&D at Rolls Royce where they made a 6 cylinder 2 stroke opposed piston.
In all my years running and working diesels I've never had a pump break, the only trouble I once had was a Scania 500 hp V8 slipped the flexible coupling to the pump and it took 10 mins to get the engine TDC and 5 minutes to fix it, I was in minus 10 degrees in Poland at the time and that fairly concentrated the mind and got me moving to get back in the warm with a mug of steaming Irish tea with a wee nip in (to help the circulation you understand).

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What is your take on the marine versions of Scania in the 300 to 500 HP range? Lord knows their base engine is common place and well received.

I've maintained scores of both. Normal maintenance is no better or worse in any relevant way.

But if I was to pick one for long distance single engine cruising, it would be the 671. I have seen injection pumps fail out of the blue on the cat, also head gaskets and rotted oil pans. And if you have any cylinder damage, the whole engine needs to come out. 671 cylinder kits can be replaced with engine in the boat, and no injection pump. Injector fails, replace it in about 20min. And even if one fails, it usually will keep running (if spring type racks!!).

But both can be excellent engines. 671 can be noisier (exhaust difficult to muffle) and will use a little more fuel to push the same boat. But it will push the boat more reliably.

Not to forget, both the 3208 and 6-71 are very old engines long out of production. There are numerous very good newer marine engines in the 200 to 300 HP range.

So buy neither is a viable option.

Your half way up the Congo River, you pull in to a little village, the local mechanic has a 6-71 gasket set hanging on the wall......

Sugardog said:

Your half way up the Congo River, you pull in to a little village, the local mechanic has a 6-71 gasket set hanging on the wall......

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But how do you get your trawler past Stanley Falls???

makobuilders said:

But how do you get your trawler past Stanley Falls???

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Use a Volvo, Mercedes or Scania, powered truck to haul the vessel maybe?