I had a 1998 150 Ficht. The first couple of 'updates' were reprograming of the Engine MAP software and different sparkplugs. That was either 1998 or 1999. Both times it resulted in slightly slower acceleration, and slightly lower top speed. Indexing of the spark plugs was another one of the updates. Also part of the updates was a recommendation to use OMC Carbon Guard fuel additive. Next came new cylinder heads. The new heads has pin/rod protruding into the combustion chamber It was supposed to scatter the fuel spraying from the fuel injector, and another remapping of the engine control module. There also some changes to the oiling system pump. A couple of years later I received what was a complete new 2003 power head. This time there was no remapping as the new engine had all the latest and greatest. It ran well enough, but as the Warranty was getting close to expiring I did some calculations what it would cost, not if, but when the new power head did self destruct. The cost of a non-warranty powerhead versus trading up to a new bigger boat with an I/O was almost identical. So I traded it. when the dealership service department did the inspection of the trade in, it noted there was already a "neat little score" on one of the cylinders. That was with 49 hours on the 'new and improved' powerhead. The "neat little score" didn't affect the agreed upon price. Where I boat, I haven't seen a Ficht on the water for many years. They just disappeared.
To do any service on the Fichts, except for changing of the sparkplugs, require special computer software, not easily obtained by non dealers.
My original powerhead always had a slight shake, like an imbalance. It was in the engine or the upper section of the driveshaft as is there in gear or in neutral. The dealer swapped another upper driveshaft but that didn't solve it, and it was still there with the new powerhead. Maybe one of the isolation mounts was bad, but the dealer changed most of those too.
The 150 fight had a WOT range of 4500 - 5500. They do a very good job of fouling the spark plugs and the Ficht combustion process will result in some very hard Soot.
Run lots of engine tuner through it and use either BRP XD50 or XD100 in it. The XD 100 will be pricey because the engine can not be reprogramed to use oil like the E-tec can. But, it is the best oil for a DI engine, TCW-3 oil, while the most current rating is not really good enough. The XD50 and XD100 far exceed the TCW3 rating, and the last time I looked, they themselves are not rated TCW3
Here is the one of the old cylinder heads, it had less than 100 hrs on it. I used nothing but OMC oil in it