What to do when those 8.1s near the end of their lives

[LG111]

Guys, pretty sure you can still buy the mercruiser 496 8.1 horizon or HO, just google. I know my mechanic orders them new for guys that want to upgrade or replace.

 

[juggernaut1]

Good to see you around Juggernaut1.

Thanks .

Been busy in my business. Unfortunately that has meant working weekends and less boating time. Although looking forward to summer holidays on the boat with the family.

 

[juggernaut1]

View attachment 77097
That is probably a good option. But they are very expensive, just as the original 8.1s are. Would probably cause an owner to look at the diesel repower option since you would be redoing the whole ER.

Yes price is on a par with the 8.1's. Apparently they use the same engine mount configuration as the 8.1's so I'm not sure how much ER work is required. I looked at some Mercruiser diesels at our local boat show a couple of years ago which I understand are based on a marinised Audi turbo v8. Price was double though and I'm guessing extensive work to mount them up with beefed up stringers to handle the torque.

 

[ttmott]

"End of Life" meaning many hours, down on power, eating oil but still solid?
The 8.1's can be safely taken to 0.030 over or sleeved to std. There is no reason the engines can't be returned to as new condition provided it is done correctly and the wear items are replaced with OEM or OEM quality. There are some modern hardware things that are now very economical and can be added to further enhance the robustness like hypereutectic piston materials, forged crankshafts, better gasketing, roller bearing valve train, high volume oil pumps, etc. A word to the wise - round file the carbs and injectors and replace with new... And, if you can get a new engine wire harness, get it.
Diesel Conversion - Gear ratio changes, cooling changes, fuel tank changes, weight and balance changes, batteries change, battery cabling changes, larger prop shafts, new props, new strut and cutlass, helm control changes, etc etc.... This conversion must be done as a passion not for economics.

 

[sbw1]

What do the 8.1 make for torque?[/QUOT]
450 pounds at 3200 RPMs. The first thing we noticed when we moved from a 370 Express weighing about 11,000 pounds to a 3200 Open weighing about 7,000 pounds more was the performance of the 8.1. Low rpm handling was much more responsive around the dock and the heavier boat popped up on plane noticeably quicker. It was like comparing a sports car to a sedan. Following sea performance was better as well. My understanding is Chevy introduced the 8.1 for towing heavy loads.

 

[sbw1]

"End of Life" meaning many hours, down on power, eating oil but still solid?
The 8.1's can be safely taken to 0.030 over or sleeved to std. There is no reason the engines can't be returned to as new condition provided it is done correctly and the wear items are replaced with OEM or OEM quality. There are some modern hardware things that are now very economical and can be added to further enhance the robustness like hypereutectic piston materials, forged crankshafts, better gasketing, roller bearing valve train, high volume oil pumps, etc. A word to the wise - round file the carbs and injectors and replace with new... And, if you can get a new engine wire harness, get it.
Diesel Conversion - Gear ratio changes, cooling changes, fuel tank changes, weight and balance changes, batteries change, battery cabling changes, larger prop shafts, new props, new strut and cutlass, helm control changes, etc etc.... This conversion must be done as a passion not for economics.

While it would be expensive, boats that were built with a diesel option might do fine without structural changes. 3200 diesel boats appear to be of identical design to the 8.1 boats. Gas tanks are the same and the stringers appear to be the same. Good to learn that 8.1s can be brought back. That is probably the way to go.