8.1L upgrades

does anyone have recommendations for performance upgrades for a 2005 SR SD 280 with the Merc 496 and Bravo 3? thanks

Pete in VT

My understanding is these engines will last forever IF left unmodified and properly maintained, they do not handle modifications well. The 8.1 high output is built slightly different to handle being run at higher RPM's with more power for extended periods of time.

I would say probably go over everything on your boat to make sure it's in tip top shape and you're getting every ounce of power you're supposed to be: spark plugs, QUALITY wires, high pressure fuel filer, fuel/water separator, injectors professionally removed and cleaned, IAC & filter, fresh motor and drive oil and at proper levels, props straight/true and polished/sharpened, fresh bottom paint with no marine growth, and make sure all your readings are on point for water pressure and temp (i.e. if your motor is running colder than 165 you're loosing power and MPGs). Also if your marina doesn't have special fuel (like valvetech marine fuel) consider putting a fuel additive with each fill up.

If you're looking for a faster hole shot or lower planing speeds consider larger trim tabs and maybe an auto-trim system that automatically deploys them during hole shot.

We have same set up as you. 496 mags with Br IIIs. Did ALL of the above and were also advised NOT to attempt to modify as would cause more issues than I could ever think of. Make sure everything stock is in proper order and you should be good. We run with several v drives that are 310s, 320s, 340s and a 380. They all tease me by calling me the rocket. My rpms top out a 4450 and my WOR speed is 46+, that is certainly fast enough.

We did re prop with the Hill Marine 4x4 props after we picked up an unmarked crab pot going thru a channel.
She is quicker to get on plain and we gained 4 mph and are staying on plain at 2950rpms rather than 3250. Of course it is always dependent on load. We are very pleased with the props and their performance. And fuel - went from average 0.9mpg to 1.1mpg - not a big leap but I will take it.

1965Cuda said:

does anyone have recommendations for performance upgrades for a 2005 SR SD 280 with the Merc 496 and Bravo 3? thanks

Pete in VT

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If you’re thinking about hardware changes like a camshaft…..don’t. Aggressive profiles and increased overlap are great mods for Street engines, but a marine engine with the “wet” exhaust system will die a very early death with an aggressive camshaft. Exhaust Reversion will almost constantly draw water from the exhaust into the cylinder and create havoc.

Espos4 said:

If you’re thinking about hardware changes like a camshaft…..don’t. Aggressive profiles and increased overlap are great mods for Street engines, but a marine engine with the “wet” exhaust system will die a very early death with an aggressive camshaft. Exhaust Reversion will almost constantly draw water from the exhaust into the cylinder and create havoc.

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And your resale value will drop hugely.

Korkie said:

We have same set up as you. 496 mags with Br IIIs. Did ALL of the above and were also advised NOT to attempt to modify as would cause more issues than I could ever think of. Make sure everything stock is in proper order and you should be good. We run with several v drives that are 310s, 320s, 340s and a 380. They all tease me by calling me the rocket. My rpms top out a 4450 and my WOR speed is 46+, that is certainly fast enough.

We did re prop with the Hill Marine 4x4 props after we picked up an unmarked crab pot going thru a channel.
She is quicker to get on plain and we gained 4 mph and are staying on plain at 2950rpms rather than 3250. Of course it is always dependent on load. We are very pleased with the props and their performance. And fuel - went from average 0.9mpg to 1.1mpg - not a big leap but I will take it.

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wondering if you stayed with the same pitch for the props? I know when switching to the 4 blade you should lose a couple hundred rpm due to increased blades/friction. I have a 260 with a single 8.1. Switched to the 4 blades and lost about 200 rpm..almost feels like she’s lugging. Same top end. Better hole shot. On plane quicker, and can hold it slower. I’m dealing with a replacement bottom drive unit with high gears though..I think somewhere around 2:4-1..running 28 pitch

Nick70 said:

wondering if you stayed with the same pitch for the props? I know when switching to the 4 blade you should lose a couple hundred rpm due to increased blades/friction. I have a 260 with a single 8.1. Switched to the 4 blades and lost about 200 rpm..almost feels like she’s lugging. Same top end. Better hole shot. On plane quicker, and can hold it slower. I’m dealing with a replacement bottom drive unit with high gears though..I think somewhere around 2:4-1..running 28 pitch

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Yes - Same pitch. That was the recommendation Hills gave me after asking if I was looking for anything thing different such as quicker on plane or higher top end. Told them I was satisfied with how she handled with the stock SS Props, so went with same.