Re the engines on new boats:
Both boats have the latest version of the MERCURY 90 FOURSTROKE. There have been about four versions of this engine. If you go shopping for used late-model Montauk boats you will encounter all four versions. Mercury calls them all with the same name, so it is impossible to distinguish among them by name. Here is some guidance.
Mercury 90 FOURSTROKE Engine Models:
The oldest Mercury 90 FOURSTROKE engines are really Yamaha engines with carburetors. They are a 1.596-liter in-line four-cylinder engine with a powerhead made by Yamaha. Mercury bought thousands and thousand of these power heads from Yamaha, and attached them to a midsection and gearcase made by Mercury. These engines had carburetors. There were notorious and chronic problems with the carburetors. These engines were called Merc-aha (as in MERCury combined with yamAHA) 90 engines, and were in production until c.2005. The cowling size was disproportionate for only a 90-HP and was more like a 200-HP two-stroke classic engine; the top of the cowling was mostly flat.
Next you can find, albeit quite rare, this same Yamaha engine but updated to have a simple electronic fuel injection fuel system. These engines should be much more service-free than the carburetor versions, but I believe they were only used for a very limited time, perhaps a year. Again, no Smartcraft. This rare model is the second-generation 90 FOURSTROKE.
The third generation 90 FOURSTROKE was a completely new, all-Mercury model, derived from the basic in-line four-cylinder design of the VERADO, but without the supercharging. This engine had a displacement of 1.7-liter. Its cowling was quite unusual, as it had a rounded dome top. This family of non-supercharged engines derived from the VERADO were called (by me and then by a few magazines) the VERADITO (from Spanish, for little or petite VERADO), as a way of distinguishing them. These engines were first made around 2006. The VERADITO is large and heavy engine, but it delivers good power and performance, and has Smartcraft. The engine has many improvements compared to prior Mercury engines:
--the fit of the cowling, the latches, and the gaskets is greatly improved from earlier engines, whose cowlings were so difficult to remove that they were almost impossible to get them off; on these engines you can actually remove the cowling without being a professional weightlifter;
--the fuel induction is accomplished in an Integrated Air-Fuel Module (IAFM) which gives the engine a much cleaner layout and a more finished and well-designed mechanical appearance.
The biggest drawback of the VERADITO is the size. This engine is just enormous for a 90-HP outboard. It is, literally, more like a 200-HP outboard in its cowling size and appearance. It weighed about 400-lbs. I think that is where the specification for maxium transom weight as 410-lbs comes from. But the performance is all good.
You can see images of both the first-version Mercury 90 FOURSTROKE and the third-version Mercury 90 FOURSTROKE in a photo-library from Warren (WT), who owned both. He had so much trouble with the carburetor MercAha engine that he was given very generous "consideration" when he traded that engine in and bought the VERADITO version:
http://smg.photobucket.com/user/warrent/library/Montauk%20Kicker?sort=4&page=1The final version of the Mercury 90 FOURSTROKE came a few years later--another completely new, all-Mercury model, with some harmony with the newer 150-HP FOURSTROKE engine, which came out in 2014. The new 150-HP engine was given the name VERADOSAURUS because its design was de-evolutionary, a throwback to simpler engines. (This naming is informal, and this engine was named by Mercury as just another FOURSTROKE model.
A thread I authored introduced the term VERADOSAURUS--to much discussion.) The "new" 90-HP engine has 2.1-liter displacement. Like the 150-HP, the "new" 90-HP seems to be designed with simple maintenance in mind, and the 90-HP version has a lot of displacement for the horsepower produced. These engines were something of a regression in technology, a throwback. They were designed for simplicity and for the owner to be able to perform routine maintenance without much trouble.
Here is another version of this history:
BRIEF HISTORY OF MERCURY 90-HP FOURSTROKE OUTBOARD ENGINE2001 TO EARLY 2006The Mercaha or YamaMerc engines--Mercury 90-HP FourStroke using Yamaha power head
--1.596-liter displacement, four-cylinder, in-line
--four-valve, dual overhead cam
--386-lbs
--carburetor fuel induction
--no SmartCraft electronic instruments
--cowing was squarish, and about the same size as a 200-HP two-cycle engine cowling.
The simplest method to identify a Yamaha engine sold as Mercury: they don't have SmartCraft electronic instrumentation.
Around 2006 Yamaha was offering their 90-HP four-cycle engine with EFI. In a 2006 Boston Whaler catalogue, the 170 MONTAUK boat is listed as having a Mercury 90-HP EFI engine, and the pictured boat has the cowling style of the Mercaha or YamaMerc engine. I haven't found a 2006 Mercury catalogue that shows this engine. There may be a few of these Mercury-brand Yamaha-block 90-HP EFI engines, or maybe not.
2006 TO 2014The VERADITO engines--Mercury 90-HP FourStroke using Verado block
--1.732-liter displacement, four-cylinder, in-line
--four-valve, dual overhead cam
--399-lbs
--simple electronic fuel induction
--SmartCraft electronic instruments
--cowling was taller and had a domed round top
IN 2014 AND AFTERThe "New" or VERADOSAURUS engines--Mercury 90-HP FourStroke using new block
--2.1-liter displacement, four-cylinder, in-line
--two-valve, single overhead cam
--359-lbs in small gear case model; 363-lbs in large gear case model
--simple electronic fuel induction
--SmartCraft electronic instruments
--cowling has new trapezoidal shape
--option of larger gear case called "Command Thrust" said to improve efficiency