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-   -   8.2L engine knowledge (https://www.offshoreonly.com/forums/general-q/387620-8-2l-engine-knowledge.html)

AmiableDave 03-16-2026 02:10 PM

8.2L engine knowledge
 
I'm looking at another boat that has 8.2 l, 380hp catalytic engines. These engines have closed cooling and have been running in freshwater. Question...
1. How many hours should an engine have before a top end is performed?
2. When should the exhaust manifolds be changed?
3. What do you have to do to make a 8.2L, 380 HP engine 430HP? Computer flash?

Thanks

MonkeySea2 03-17-2026 11:27 AM

these engines will run well over 1000 hrs before major overhaul. Manifolds, IMO, are dependent on where it's run. I just traded my 496 with 550 hrs. on it and never did the manifolds. I just inspect them.

I think there's more to it than a flash. I wanna say cam and other stuff....

AmiableDave 03-17-2026 01:02 PM


Originally Posted by MonkeySea2 (Post 4944632)
these engines will run well over 1000 hrs before major overhaul. Manifolds, IMO, are dependent on where it's run. I just traded my 496 with 550 hrs. on it and never did the manifolds. I just inspect them.

I think there's more to it than a flash. I wanna say cam and other stuff....

Thank you for your time and experience in such matters.

Brad Christy 03-17-2026 01:04 PM


Originally Posted by AmiableDave (Post 4944560)
I'm looking at another boat that has 8.2 l, 380hp catalytic engines. These engines have closed cooling and have been running in freshwater. Question...
1. How many hours should an engine have before a top end is performed?
2. When should the exhaust manifolds be changed?
3. What do you have to do to make a 8.2L, 380 HP engine 430HP? Computer flash?

Thanks

Dave,

Not at all the same engine, but the only real differences between the 496MAG and the 496HO is the cam and the ECM flash. I'd imagine it's the same with the 8.2.

Thanks. Brad.

F-2 Speedy 03-17-2026 01:15 PM

Here is some good and bad about these engines, dont know what year engines you are looking at, maybe mother Merc have these fixed ?

https://www.offshoreonly.com/forums/...er-engine.html

techman 03-18-2026 01:33 PM


1. How many hours should an engine have before a top end is performed?
If it's bone stock and well maintained with a well documented service history you can go well past 1000 hours plus. This not a HP motor so the top ends will outlast your ownership most likely.


​​​​​​​2. When should the exhaust manifolds be changed?
When they need to be. They don't self destruct at a certain hour. Fresh water is a BIG help in longevity.


​​​​​​​3. What do you have to do to make a 8.2L, 380 HP engine 430HP? Computer flash?
Cam and ECU, but I wouldn't bother. I have yet to see anyone, or the benefit, from the hassle of making a SO an HO. If you are hesistant on the power than look for another boat with the engines you want.






F-2 Speedy 03-18-2026 02:11 PM

I was kind of surprised these run two ECU's..........one for engine management and the other for emissions and they are linked together through some type of gateway.

techman 03-18-2026 02:39 PM


Originally Posted by F-2 Speedy (Post 4944679)
I was kind of surprised these run two ECU's..........one for engine management and the other for emissions and they are linked together through some type of gateway.

yeah...these engines are not easily tinkered with. That why I think trying to make a SO to an HO is not worth it.


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