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1994 Detroit Diesel 8.2L

Old 09-12-2017, 04:34 AM
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Default 1994 Detroit Diesel 8.2L

I am looking at a Mainship the original Detroit Diesels replaced with rebuilt updated engines by Johnson & Towers (1994) and have 1197 original hours. Does anyone know these engines/opinions? I know there was some issue with head bolts and manifolds do they apply to this motor?
Old 09-12-2017, 05:47 AM
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Unless the boats is way below market price, I'd avoid these engines. Parts are a challenge to find and expensive. A friend has them in his Blackwatch and has spent a fortune keeping them together. Lastly, if when you decide to sell the boat, it will reduce your price.
Old 09-12-2017, 05:52 AM
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Agree, better to factor in the cost of replacing with a reman Cummins if the budget allows for it. The 8.2 was a marketing fail for the marine business.
Old 09-12-2017, 06:16 AM
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The problem with those engines was that they were very temperature sensitive, if you overheat them they will crack the exhaust manifold, at least at the begining, DD worked on this problem by adding a water hose to increase the cooling of the manifold, also the salt water pump was belt driven, I never understood why the alternator had 2 belts and the pump only one. They are similar to the cat 3208 in the sense that they do not have removable liners. In general they are not that bad you just have to be carefull of your engine temp do not let them overheat. In the 1980ś I repowered a Bertram 31 with a pair of them, the 250 HP version, I believe the Aftercooler version jumped the horsepower to 300 HP, and the boat really run fast, they were light and had a small footprint.
Old 09-12-2017, 06:24 AM
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I can see now why the price is so low. Boat seems to be in good shape for its age, but I can't see having to replace engines.
Old 09-12-2017, 07:09 AM
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Hello, those engines unfortunately were not a great success for DD, they actually started life as gas motors and then converted for use with diesel, the blocks are not as strong as a true diesel engine, they had a lot of cooling problems too. Parts seem more difficult to come by than regular 2 stroke DD motors. If the seller has a huge file of old invoices and maintenance records then it might be worth a punt otherwise for me I think it would be a deal breaker, just my 02 cents. Hope this helps.
Old 09-12-2017, 07:52 AM
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Are the problems specific to one year or multiple years?
Old 09-12-2017, 08:00 AM
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Originally Posted by larryny View Post
Are the problems specific to one year or multiple years?
Good question, like the other poster said, there were improvements as time went on, mostly with regards to cooling.
Old 09-12-2017, 08:29 AM
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Originally Posted by buxa View Post
Hello, those engines unfortunately were not a great success for DD, they actually started life as gas motors and then converted for use with diesel,
I'm not sure this is true. But I do lots of these 8.2 "fuel pincher" engines were put in school buses.

In the 80's I think DD did a design change and put larger head bolts on them to reduce head gasket failure.

The are not desired power, but if they run well and have 1000+ hours on them and the owner didn't beat them, it's not unreasonable to expect them to run another 1000 hours. Especially if you are going slower or doing a slow cruise.
Old 09-12-2017, 09:44 AM
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Everyone that has posted is pretty much right here. I had them and your biggest issue is getting parts and re-sale. You can get more for a boat with gas engines than you can JT 8.2's due to parts and internet reputation.


Someone mentioned they are light, but they are not. I lost over 1200 pounds going from 8.2 Detroits to 370 Cummins. I sold the engines for not much more than I would have got to scrap them for the metal.
Old 09-12-2017, 09:54 AM
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Unless a $65k repower for reman Cummins 330B's or 370B's is in your budget - run.
Old 09-12-2017, 12:37 PM
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Originally Posted by larryny View Post
I am looking at a Mainship the original Detroit Diesels replaced with rebuilt updated engines by Johnson & Towers (1994) and have 1197 original hours. Does anyone know these engines/opinions? I know there was some issue with head bolts and manifolds do they apply to this motor?
The J&T's make 300 hp while the standard engines made 250. That extra 50 hp was expensive to make. Many parts are not interchangeable. J&T parts are harder to find that parts for standard 8.2, A friend of mine had a very hard time finding a J&T exhaust manifold when he needed one. Another friend blew a fuel solenoid on his engines regularly. I'd stay away unless you can get the boat so cheaply, you can afford to repower it.
Old 09-14-2017, 08:26 AM
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Originally Posted by riprunner View Post
Everyone that has posted is pretty much right here. I had them and your biggest issue is getting parts and re-sale. You can get more for a boat with gas engines than you can JT 8.2's due to parts and internet reputation.


Someone mentioned they are light, but they are not. I lost over 1200 pounds going from 8.2 Detroits to 370 Cummins. I sold the engines for not much more than I would have got to scrap them for the metal.
This is accurate. I'm currently running twin 8.2s by J&T at 300 hp. Parts are pretty much unavailable. There is an easy fix for the cracking exhaust manifolds, but if you a cracked manifold a replacement is unavailable. If you have the 300 hp version, make sure the head bolts were upgraded or run her easy. I'm in the process of replacing hoses. A lot of the hoses were custom J&T hoses that are no longer made. I've figured out substitutes, but it wasn't easy. They're great on fuel, and if taken care of, guys have gotten 10,000 plus hours out of them. First big problem, and I'm repowering with Cummins. Total lack of a available parts is the biggest issue, and it's pretty much a show stopper.
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