2006 Mercury 90: Convert to 115-HP

[Fantasea Camp]

The cylinder heads on my 2006 Mercury 90-HP engine are being replaced due to corrosion. Since the bottom end is in fine shape and I want this done properly and cost effectively, I am going to move forward with the expensive repair.

Since I am already on the hook for a $2,200 re-built head, maybe I can increase power by bolting on a 115-HP cylinder head and replacing the ECM.

Will it work?

[jimh]

Attempts to produce more horsepower in a engine by adding a few parts to make it a higher-horsepower version are often the topic of speculation, as we have in this thread, but generally these conversions are not particularly easy or cost effective. There may be many small changes in various parts. For example, if the engine uses carburetors the fuel metering jets may be different. And as you know, the engine control module may also need to be reprogrammed or to be actually physically different.

In some particular engines, all that may be needed is to load new firmware into the engine control. I believe that in the early VERADO FOURSTROKE engines there was essentially no difference physically or mechanically between, say, a 200-HP and a 250-HP model, for example. Loading new firmware--if you could get it--would immediately produce a more powerful engine. The problem is getting the firmware and the necessary cables and knowledge to alter the engine control module.

The obvious problem is manufacturers do not hand out that sort of firmware for their own interest--they want you to pay more for more horsepower. A less obvious problem is emission regulations do not allow a regulated engine to be modified in any way to alter its emission, so fiddling with an engine may be illegal under federal regulations. In 2006 spark-ignition outboard engines were, I believe, subject to those EPA regulations.

[biggiefl]

Pretty much what Jim said. If the specs are the same for a 90 and 115 and it is a 4 stroke, usually the ECM and maybe the throttle body are different. How you can usually tell is higher rpms for the higher HP engine. My 40 Suzuki is identical to a 50hp. Mine redlines at 5800 and the 50 is like 6200. As Jim said with the Verados, some had different WOT range and some required premium unleaded or else the ECM would restrict the HP. Not easy to do like Jim said and personally I would probably not mess with it.