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Old 08-14-2020, 08:54 PM   #21
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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.
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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Old 09-15-2020, 11:25 AM   #22
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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.
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Old 09-15-2020, 12:21 PM   #23
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Originally Posted by RentonRiggos View Post
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.
Welcome aboard. I am not familiar with your engines so I will leave comments on them to someone more knowledgeable than me.
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Old 09-15-2020, 02:06 PM   #24
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Quote:

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.
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).




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Old 09-15-2020, 02:17 PM   #25
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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. .
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Old 09-15-2020, 02:25 PM   #26
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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).




_

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°.
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Old 09-15-2020, 10:02 PM   #27
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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.
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Old 09-16-2020, 10:07 AM   #28
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Originally Posted by Rufus View Post
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.


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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?
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Old 09-16-2020, 10:21 AM   #29
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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.
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Old 09-16-2020, 11:06 AM   #30
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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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Old 09-16-2020, 01:17 PM   #31
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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?
I believe the block, heads, head gaskets, and reciprocating components are the same for all of the turbocharged models. Sixteen years ago in preparation for making the decision to purchased our boat, I called Johnson and Towers to see if any of their original 8.2 certification engineers were still around. Lo and behold they connected me with an "old" gent who was part of the original JT certification team. If I remember his comments correctly, the original turbo truck engine was at 180 HP. He explained that the subsequent horse power increases to 220 and the 250 were achieved by simply increasing injector size. For the 300 engine they upped injector size once again and added an intercooler. But nothing changed in the core engine....even the same cam profile for the injectors. So percentage of rated power is somewhat misleading. They ultimately loaded that head gasket to the failure point. And from my discussions with two rebuilders through the years, the preponderance of head gasket failures were in smaller sport fish boats with the 300 HP engines....running near max power for extended periods. Lose a raw water pump at very high power and the gasket would likely pop pretty quickly...

Regarding carbon buildup from running at slow speeds...yes it does concern me. So I do the standard run up to higher power once every couple of hours. And that does visibly clean up the exhaust. The other thing I did a couple of years ago is switch to Rotella synthetic T6. That seems to have helped. Something else that I've wondered about is downsizing to the 220 HP injector spec. I don't need the high end power anyway. Think I'll call J&T again....

PS Detroit Diesel, J&T and Stewart and Stevenson each used a different exhaust manifold casting. I suspect that this has been a source of parts availability issues over the years. In any case, Mesa Marine Exhaust can make any of them.
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