Questions about Detroit 8.2L engines

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Alaska JD

Member
Joined
May 12, 2020
Messages
24
Location
USA
Vessel Name
Arctic Jade
Vessel Make
Ocean Alexander 42
I am new to the trawler forum. A year ago we sold our sailboat and have/are making the switch to what some have called “The Dark Side” :eek:. (We are thinking simply enlighten :)) While I have a bunch of experience with a variety of sailboats I’m just learning about trawlers. My wife and I are actively shopping for a trawler in the 40 - 45’ range. Some of the boats we are interested in have Detroit 8.2L diesels. My research indicates they tend to have significant problems. On the other hand, some on this forum report having them for years, requiring little more than routine maintenance and TLC. Are there any key indicators a good engine survey would discover that could give me a thumbs up or down on the Detroit 8.2L engines in a boat we’re interested in? My wife and I are used to sailboat speeds and not interested in going fast. Seeing a consistent 8 - 10 knots would be wonderful. Obviously boat weight and configuration are determining factors on how much power it takes to make that speed. Again, the Detroit 8.2L is the issue. Thanks in advance for any and all thoughts and reported experience.
 
whether you think they are a good engine or not, parts availability is problematic.

I had 2 , never again
 
I helped a friend move a boat with an 8.2 and lived with it for a week. Before the trip I researched this forum, boatdiesel, etc. I discovered that head bolts were a weak point and if you planned to run the least bit hard then upgrade them. The other weakness was the cooling system and there was a straightforward fix that consisted of a vent from the rear cylinder.

But if you ran them easy, say 100 hp each they would be fine with no upgrades and were as solid as any engine.

David
 
I personally know of two owners who swapped out their pair of 8.2s. One went with JD 6068s and the other with Cummins 5.9TAs. In both cases the 8.2s had less than 1,500 hours.

Someone can correct me on this but I don't recall the DD 8.2s had much more than a 6 year build life. DD's 6-71 is generally regarded as a much better choice if you want a DD.
 
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Much has been written on 8.2 Detroits at boatdiesel.com. You'll get lots of options there. In their defense, I have two friends who have them and like them.
 
8.2s are nowhere near as reliable as the previous 2 cycle Detroits. I never owned one but worked on a couple. They tend to blow head gaskets when under near full power and had overheat problems. They also had a head bolt problem getting proper torque. If run easy they last about as good as most yacht engines and are more fuel efficient than older Detroits. You can get parts and rebuilt engines.

I'd rather burn more fuel and have a reliable engine.
 
I have two low hour engines in our OA for Fifteen years and counting. Zero issues...ever. The head bolt issue was addressed by the factory years ago...mid-80’s. I run them vey conservatively...mostly hull speed. No doubt they have thousands of hours left in them. Some posters here speak from experience with trucks where the engines demanded more than normal maintenance time and tended to be in light duty trucks with poor access. Hence they were abused and ran poorly. In a boat the injector racks get set at an rpm and are not in constant motion as for a truck with an accelerator pedal. They are well known to be very fuel efficient. Parts are comon on e-bay. Good used engines show up on wrecking yard sites all the time. Water pump rebuild kits are available. Even new turbos. The only item that might be scarce are marine exhaust manifolds, but I believe Mesa has them (expensive). While I haven’t had to replace anything, I do keep an eye out for spares. I just don’t get the comments about parts being difficult. Are these current owners making these remarks??

There are quite a few of these engines in boats and you simply don’t see owners posting about issues on this forum for sure Certainly nothing close to posts associated with Lehman’s, Cats, Volvo’s, 2-stroke Detroit’s, and even Cummins from the same era. That’s the real world test. Those of us who have them, like them. Just don’t run them hard for extended periods. Treat them like the vaunted Lehman’s get run and they’ll run longer at lower fuel consumption. The only engine From that era that I consider to be in the same league might be the single non-intercooled turbo Cummins. Whenever this comes up the same detractors (who have never personally owned and run them in a boat chime in about engines they worked on long ago or someone they knew who had them. Take that anecdotal “stuff” with a large helping of salt.
 
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Relative to DD 2 strokes, parts are in deed scarce and expensive. The same can be said for the Cummins 555 engine. There are many engines that fall into this category. You won’t find DD 8.2 engines in any go fast boats, they died long ago. You will still find them and the 555 in low demand applications.

The head gasket issue is never going away on an 8.2. It only has 10 head bolts while the other engines have 18. Upsizing the bolts helped the issue but did not completely solve the issue. Running the engines moderately does seem to solve the issue.

Not knowing the application and intended use of the engine one has to give an opinion on how an engine performs across the board. 8.2’s earned their reputation and you see that reflected in this forum.

I would try to avoid this engine but if it’s your dream boat then you need to know it’s limitations.
 
I have no experience with them but they do seem to have a bad reputation. So take that into account if you ever want to sell it, it probably will make it more difficult to sell. Oh, BTW welcome aboard.
 
I truly appreciate the feedback. My wife and I are actively shopping for a trawler, and us really liking a couple of OAs we’ve seen, but me being spooked by the engine’s reputation prompted my questions to the wisdom of this forum. I’ve not yet had a survey done, but we’re coming very close. I’ve also considered the cost of repowering with smaller engines as we go back to our live-aboard life-style. With any luck and lots of TLC, I’ll never need to worry about repowering. Thanks again for everyone’s input.

John
 
Repowering is fine to do as long as you realise that when you eventually sell you will get low return on the dollars you spend doing it. But fine if you are keeping the boat for 10-15 years to get the benefit of new engines.

As noted in another thread recently, old Taiwanese boats have some or all of well known issues: deck cores deteriorated from screwed-in teak, leaking windows, rusted fuel tanks and poor quality plywood delaminating. The time to consider a repower is if you pull the engines to replace fuel tanks, which is what I did. You will get a bit of money back from selling running take-outs.
 
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Very good point about the return on the dollar for repowering. Good engines make the boat sell faster, not for more money. Also your comments about Taiwanese boats of earlier vintage is well noted. There are some things even the best, most thorough surveys don’t catch. They only become evident with fuel in the bilge or some other nasty surprise.
 
Very helpful information. Thank you so much. What prompted this question is interest in an OA 42
 
.....a few more thoughts. Our OA has a very loud audio alarm that goes off at 205 degrees F engine temperature. I had a raw water pump throw a belt some years ago while I was driving from the fly bridge. A glance it the temperature gauges showed the starboard engine at guess what....205 degrees. A press of the red shutdown button cut off the fuel and I fixed the problem enroute. Had I let it overheat a head gasket issue might have ensued. You want to be sure that alarm is functional on both engines and keep an eye on water temperature. How dang difficult is that?

But even if the engine had blown a head gasket, odds are that the fix would have been as simple as replacing it. I don’t get the “replace” the engine or re-engine talk. Why?
 
205 F is pretty typical for an alarm set point. If the cooling system is filled with 50/50 antifreeze you have until at least 230 deg F before the system starts boiling dry and then time to react before it goes dry and ruins the head gasket and possibly the head.

But a Borel alarm is always a good idea on a marine engine. It alarms when the exhaust gas below the mixer exceeds 165 F which gives you even more time to react.

David
 
Alaska JD said:
On the other hand, some on this forum report having them for years, requiring little more than routine maintenance and TLC. Are there any key indicators a good engine survey would discover that could give me a thumbs up or down on the Detroit 8.2L engines in a boat we’re interested in? My wife and I are used to sailboat speeds and not interested in going fast. Seeing a consistent 8 - 10 knots would be wonderful. Obviously boat weight and configuration are determining factors on how much power it takes to make that speed. Again, the Detroit 8.2L is the issue. Thanks in advance for any and all thoughts and reported experience.
Click to expand...


We had a single 8.2T in the '87 34' Mainship we had back in the early '90s. Johnson & Towers did a "recall" (service bulletin) to upsize the headbolts. Did that, all good, we never had issues and as far as I know that engine is still in service with the new owner.

It wasn't uncommon back then to see twin 8.2Ts in 34-40' boats with planing hulls.

Depending on how those engines have been maintained, and depending on your intended method of operation, I don't think I'd be scared away. There was another thread sometime not too far back where Fred (FF) was musing about a boat with 8.2T power, and I think the end theory is that in his case it'd be OK to get the boat, run it, worry about it down the pike if problems arise. Read that thread, if you haven't already...

-Chris
 
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"It wasn't uncommon back then to see twin 8.2Ts in 34-40' boats with planing hulls.

Depending on how those engines have been maintained, and depending on your intended method of operation, I don't think I'd be scared away. There was another thread sometime not too far back where Fred (FF) was musing about a boat with 8.2T power, and I think the end theory is that in his case it'd be OK to get the boat, run it, worry about it down the pike if problems arise. Read that thread, if you haven't already..."

The boat I was after was a Tom Fexas 44ft Midnight Lace, a fine inshore boat for a couple. I love the fwd cockpit , and decided , if not now , when?

The hassle is the boat was seldom used , so came up for sale.Asking $80K

MY GUESS was the seller or broker decided to run on the pin for too long and overheated one engine. The engine was removed and sent to a truck repair shop , when returned it still did not work , so was sent back again.

That's when I lost interest.

Another Lace in TEXAS lost its engines and 2 Volvos with new V drives was installed.

About $40K worth of engines plus the install. The engines are under the cockpit sole so it shouldn't have been too bad.

The price was asking $135k.Not a bad deal but I am not a Volvo fan., I cold have been OK with the Volvos but other hassles arose.

The builder uses GRP fuel and water tanks , my favorite , but for some reason they were removed. The concept of living with metal tanks was enough to be a big turnoff.

I have made an offer (a low ball) for the Texas boat , thinking if its accepted any tank work or engine repair will be contracted out with the money saved.

Who knows , fingers crossed , still waiting.
 
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I had 2 in a boat I had in the late 80's, early 90's with 8.2's. Mine had the headbolt upgrade as well. Great on fuel, hard to find parts for,hard to find people who are familiar with them and willing to work on them. Local Detroit dealer only had 2 techs trained on them. I would think its a much harder task chasing parts today. Not "Dock talk", truck talk or other talk. Real world owner who put hours on mine. My DD tech told me parts situation would be getting worse as engines had been discontinued years before. And that was 30 years ago..
 
Sailor of Fortune said:
I had 2 in a boat I had in the late 80's, early 90's with 8.2's. Mine had the headbolt upgrade as well. Great on fuel, hard to find parts for,hard to find people who are familiar with them and willing to work on them. Local Detroit dealer only had 2 techs trained on them. I would think its a much harder task chasing parts today. Not "Dock talk", truck talk or other talk. Real world owner who put hours on mine. My DD tech told me parts situation would be getting worse as engines had been discontinued years before. And that was 30 years ago..
Click to expand...

So what parts failed on your engines that were difficult to find in the late 80s and early 90s? Complete engines are still easy to come by. I have one pickled in my garage, along with a new in the box: set of turbo pistons/rings, new cam, head gasket sets, fuel pumps, fuel shutoff solenoids, bearing set, water pump rebuild kit, and a complete set of tools for setting injectors. Then there’s the spare water pump, starter, and governor set up. No there isn’t a dealer parts network, but parts are around. By the way, I bought all these things along the way because I mistakenly bought into the dock talk and thirty year old conjecture. I haven’t touched a single one of those spares in fifteen years.

There’s no rocket science in the design. The only thing that’s arguably unique is the cam actuated injection carry over from the 2-strokes. When I read about injection pump/system issues on Lehman’s and Cats, parts supply/cost issues with Volvo’s, the recent thread regarding #6 cylinder meltdown issues on Lehman’s, I conclude that the design of the 8.2 (head sealing aside) was a stroke of genius for a small marine engine. Respect the well known head gasket issue and the engine will keep on keepin’ on.

Of course dealers were reducing support for the engine by the mid-90s. Your engine tech’s remarks were no doubt speculation based on what was happening with Detroit Diesel. The internet took up the slack. I found a diesel shop in remote northern Michigan that has a mechanic who is knowledgeable with the 2-stroke injection set up if I have a need. But I also have the excellent shop manual and adjustment tools. It ain’t rocket science.
 
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Rufus said:
So what parts failed on your engines that were difficult to find in the late 80s and early 90s? Complete engines are still easy to come by. I have one pickled in my garage, along with a new in the box: set of turbo pistons/rings, new cam, head gasket sets, fuel pumps, fuel shutoff solenoids, bearing set, water pump rebuild kit, and a complete set of tools for setting injectors. Then there’s the spare water pump, starter, and governor set up. No there isn’t a dealer parts network, but parts are around. By the way, I bought all these things along the way because I mistakenly bought into the dock talk and thirty year old conjecture. I haven’t touched a single one of those spares in fifteen years.

There’s no rocket science in the design. The only thing that’s arguably unique is the cam actuated injection carry over from the 2-strokes. When I read about injection pump/system issues on Lehman’s and Cats, parts supply/cost issues with Volvo’s, the recent thread regarding #6 cylinder meltdown issues on Lehman’s, I conclude that the design of the 8.2 (head sealing aside) was a stroke of genius for a small marine engine. Respect the well known head gasket issue and the engine will keep on keepin’ on.

Of course dealers were reducing support for the engine by the mid-90s. Your engine tech’s remarks were no doubt speculation based on what was happening with Detroit Diesel. The internet took up the slack. I found a diesel shop in remote northern Michigan that has a mechanic who is knowledgeable with the 2-stroke injection set up if I have a need. But I also have the excellent shop manual and adjustment tools. It ain’t rocket science.
Click to expand...
Exhaust manifolds... Have you tried to find one? If your a 200 hr a year or less yacht, the engine may be fine for your service. I put hrs on mine. I was brought up with 2 cycle dDetroits and expected the same type of hrs ...Not going to happen.Some people were happy with Edsels, Corvairs, and Chevy Vegas....
 
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I am brand new to trawlerforum (and forums in general). I hope I am posting properly.

Interesting Discussion. I see many of the questions I was asking myself 4-5 years ago when I bought our boat with 2 DD 8.2T engines w/950 hours. I still have questions about their suitability and best operation but they have worked for me so far.

Here are my observations:
1. Every other mechanic tells me to replace them. In between the others tell me they are great. Latest mechanic (a DD fan) is telling me they are great
2. Can't speak to parts availability as nothing has failed. I have only added about 300 hours (60-70/year). My services company has told me they can get the "normal" ones if needed (manifolds, etc.)
3. I have them checked yearly (tune/oil change). Only issue is that they cant seem to get the engines tuned to idle at the same RPM (approximately 50RPM different). This may be caused by a linkage wearing. Need to revisit with the shop. Maybe a parts issue?
4. I am seeing some issues with my starters. They are missing approx. 1 out of 10 starts. I will pull the starters this winter and get them rebuilt. I am assuming it is an age problem not an operating hours problem.
5. I have had the temp alarm go off twice (I immediately shut them down) both times due to raw water belt breaking (figured out how to fix the alignment issue after second time). Didn't seem to cause any lingering issues.

Questions:
1. I run mine at about 2650 RPM (approx 17kts) pretty consistently. I rarely hit 2800 and have hit 3000-3100 only for a minute or two. I was told 2600-2800 was an OK RPM to run consistently, I saw one of the posts here and it talked about these being good engines in the right service. Is this a decent way to treat them or should I throttle back?
2. After the next couple of years we will be using the boat significantly more (planned 250+ hrs/yr). Do I need to treat the engines differently at that point in terms of what RPM I run at?
3. I have thought about a repower (modern technology, space in engine room) but have not since it was too expensive and frankly there is not a compelling reason currently. If I was planning to trade up in boats in the next 5-7 years should that change my thinking or will a well maintained boat with operational low hour DD 8.2T's still be salable.

I appreciate any feedback.
 
RentonRiggos said:
I am brand new to trawlerforum (and forums in general). I hope I am posting properly.

Interesting Discussion. I see many of the questions I was asking myself 4-5 years ago when I bought our boat with 2 DD 8.2T engines w/950 hours. I still have questions about their suitability and best operation but they have worked for me so far.

Here are my observations:
1. Every other mechanic tells me to replace them. In between the others tell me they are great. Latest mechanic (a DD fan) is telling me they are great
2. Can't speak to parts availability as nothing has failed. I have only added about 300 hours (60-70/year). My services company has told me they can get the "normal" ones if needed (manifolds, etc.)
3. I have them checked yearly (tune/oil change). Only issue is that they cant seem to get the engines tuned to idle at the same RPM (approximately 50RPM different). This may be caused by a linkage wearing. Need to revisit with the shop. Maybe a parts issue?
4. I am seeing some issues with my starters. They are missing approx. 1 out of 10 starts. I will pull the starters this winter and get them rebuilt. I am assuming it is an age problem not an operating hours problem.
5. I have had the temp alarm go off twice (I immediately shut them down) both times due to raw water belt breaking (figured out how to fix the alignment issue after second time). Didn't seem to cause any lingering issues.

Questions:
1. I run mine at about 2650 RPM (approx 17kts) pretty consistently. I rarely hit 2800 and have hit 3000-3100 only for a minute or two. I was told 2600-2800 was an OK RPM to run consistently, I saw one of the posts here and it talked about these being good engines in the right service. Is this a decent way to treat them or should I throttle back?
2. After the next couple of years we will be using the boat significantly more (planned 250+ hrs/yr). Do I need to treat the engines differently at that point in terms of what RPM I run at?
3. I have thought about a repower (modern technology, space in engine room) but have not since it was too expensive and frankly there is not a compelling reason currently. If I was planning to trade up in boats in the next 5-7 years should that change my thinking or will a well maintained boat with operational low hour DD 8.2T's still be salable.

I appreciate any feedback.
Click to expand...

Welcome aboard. I am not familiar with your engines so I will leave comments on them to someone more knowledgeable than me.
 
Questions:
1. I run mine at about 2650 RPM (approx 17kts) pretty consistently. I rarely hit 2800 and have hit 3000-3100 only for a minute or two. I was told 2600-2800 was an OK RPM to run consistently, I saw one of the posts here and it talked about these being good engines in the right service. Is this a decent way to treat them or should I throttle back?
2. After the next couple of years we will be using the boat significantly more (planned 250+ hrs/yr). Do I need to treat the engines differently at that point in terms of what RPM I run at?
3. I have thought about a repower (modern technology, space in engine room) but have not since it was too expensive and frankly there is not a compelling reason currently. If I was planning to trade up in boats in the next 5-7 years should that change my thinking or will a well maintained boat with operational low hour DD 8.2T's still be salable.
Click to expand...

RPM doesn't tell you much about how hard the engines are working. A prop demand chart combined with a speed/rpm polar paints a pretty good picture. Our boat makes 15 knots at 2650, and they're producing about 160 horsepower each per the prop chart. Max is 250 HP. I prefer to run them at power required for hull speed "plus" (8.4-8.5), which is 15-1600 RPM. The only time I push the engines to the mid-2000's rpm is when I'm trying to make a bridge opening or adjust the "ride" if it's choppy. I'm absolutely confident that they'll be running just fine for decades. My advice would be to slow down, but without a prop chart for your boat, that's a bit of a WAG.

By the way, a previous poster mentioned a scarcity of exhaust manifolds, so I contacted Mesa Marine Exhaust. They have blueprinted the manifolds from J&T, Detroit Diesel and Stewart and Stevenson. They can fabricate any one of them in short order (so too could any competent machine/welding shop I suspect). Mesa also sells marinization kits for a few older truck/tractor diesel engines (no complicated emissions).




_
 
Poorly designed engine with almost no decent support these days. They could handle street loads moderately well with life cycles on par with good gas engines. However they certainly couldn’t hold up to the constant loads of a marine drive train. Back in the 90’s they were laying around in boatyards and outside of shops as repower discards with no value other than parts. It took the factory a long time To acknowledge design defects such as stretched head bolts and longer to effect a retro fit. By then there was no salvation for these engines, the word was out. I can tell you that selling a boat with these coupled to your shafts is a major valuation deflator. And they don’t compare at any level with Detroit’s famous two cycle 53’s, 71’s, 92’s or even the great old 110’s. .
 
Rufus said:
RPM doesn't tell you much about how hard the engines are working. A prop demand chart combined with a speed/rpm polar paints a pretty good picture. Our boat makes 15 knots at 2650, and they're producing about 160 horsepower each per the prop chart. Max is 250 HP. I prefer to run them at power required for hull speed "plus" (8.4-8.5), which is 15-1600 RPM. The only time I push the engines to the mid-2000's rpm is when I'm trying to make a bridge opening or adjust the "ride" if it's choppy. I'm absolutely confident that they'll be running just fine for decades. My advice would be to slow down, but without a prop chart for your boat, that's a bit of a WAG.

By the way, a previous poster mentioned a scarcity of exhaust manifolds, so I contacted Mesa Marine Exhaust. They have blueprinted the manifolds from J&T, Detroit Diesel and Stewart and Stevenson. They can fabricate any one of them in short order (so too could any competent machine/welding shop I suspect). Mesa also sells marinization kits for a few older truck/tractor diesel engines (no complicated emissions).




_
Click to expand...


Good points but actually one of the most reliable indicators of a diesel load is exhaust temp. The harder a diesel runs or works the higher the exhaust temp. For many years Caterpillar installed pyrometers on their older ‘ D ‘ type engines just for this reason. The factory told you to pretty much ignore the tach and watch the pyro. Those old 20-40K hour engines liked it around 1200° and if you pushed them they would climb right up to 1400°.
 
The cost to repower compared to the value of the boat makes more sense on a $350k boat vs a $140k boat. You don't mention the price of the boat you're looking at. Gauges, wiring, transmissions shaft size...so many things may need to be changed on a repower for two engines. Not the way I'd want to start my life with a boat. But do what's right for you.
 
Rufus said:
RPM doesn't tell you much about how hard the engines are working. A prop demand chart combined with a speed/rpm polar paints a pretty good picture. Our boat makes 15 knots at 2650, and they're producing about 160 horsepower each per the prop chart. Max is 250 HP. I prefer to run them at power required for hull speed "plus" (8.4-8.5), which is 15-1600 RPM. The only time I push the engines to the mid-2000's rpm is when I'm trying to make a bridge opening or adjust the "ride" if it's choppy. I'm absolutely confident that they'll be running just fine for decades. My advice would be to slow down, but without a prop chart for your boat, that's a bit of a WAG.


_
Click to expand...

Thanks. I appreciate the details and feedback. final details: My engines are rated 300HP at 3200 RPM and I have a roughly 24kt max speed. Since I don't have a prop demand chart... and using the rough estimate of speed varying by the square root of power. My estimate is I am developing 150HP at 2650/17kts. Would it make a difference in terms of your advice on slowing down that I am at 50% load at 2650RPM versus 64% load for you at 2650RPM? Also is there a problem with carbon buildup running them at 15/1600 RPM for extended periods?
 
Hopefully someone can answer that question for you. I'd like to point out that the historical use of the engines can't be changed. If the log book documents the engine speeds throughout it's life, you have a valuable accounting to guess the engine use/abuse. Hope this is useful info to you, it's really for all people who are boat shopping.
 
A good way to ensure you are not overloading the engines at cruise speeds is to test your WOT RPMs. If your engine is rated at 3200 RPM, you'll need to make sure you can reach at least 3250 RPM at WOT typically loaded. If that is the case, then cruising at 80% rated RPM (i.e 2550) should be fine.

Even then it is possible to overload engines climbing typical West Coast swells in a planing boat. E.g., climbing a 6 foot swell with a period of say 12 seconds (very tolerable) at cruise speeds will put a lot of stress on the engines. My EGTs routinely increased 20% climbing the swells. Just something to be aware of. You may have to significantly throttle back in large swells if you do not have EGT gauges to verify load. Wind can have a similar effect although wind waves will force you to throttle back most time anyway.
 
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