A Brief History of the Mercury 90-HP FOURSTROKE

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jimh
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A Brief History of the Mercury 90-HP FOURSTROKE

Postby jimh » Thu Jul 13, 2017 1:22 pm

There have been about four versions of the MERCURY 90 FOURSTROKE. 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, first-generation 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 for 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 system. These engines should be much more service-free than the carburetor versions, but I believe they were only made for a very limited time, perhaps a year. Again, no Smartcraft. This rare model is the second-generation 90 FOURSTROKE EFI.

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 a 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 for some Boston Whaler boats that used this engine. 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 ... t=4&page=1

The final version of the Mercury 90 FOURSTROKE came a few years later in c.2014--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 90 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 ENGINE

2001 TO EARLY 2006

The 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 2014

The 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 AFTER

The "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

swist
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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby swist » Fri Jul 14, 2017 2:16 pm

As an owner of the recent 2.1L engine with "command thrust", I have to agree that there is a change of direction here along the lines of simplicity and maintainability. I would note that the shop manual for the engine is VERY different from the previous Mercury manuals I have owned. It is much more detailed, with step-by-step instructions broken down to the smallest of operations. It also has tables suggesting "if you have this symptom, look for this problem". You would have to guess the assumption is that owners, in addition to Mercury mechanics, may well find some repairs quite doable with this degree of detail. The effort that went into this book is quite remarkable.

But back to the engine, only time will tell if the design strategy will pay off. I will say anecdotally I'm very impressed with the engine. It is almost silent at idle, smoother and quieter at higher speeds than any other outboard I have owned, and between the command-thrust gearbox and the 2.1L displacement, has rather impressive low-end torque - I dare not jump on the throttle too much from a dead start for fear of throwing passengers out of the boat.

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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby pcrussell50 » Thu Aug 03, 2017 12:40 pm

I have not had the least bit of problem with my 2000 carbureted 90hp FourStroke that could be attributed to being a carbureted motor. Further, when I spent July of 2016 in a Mexican fishing town, (San Carlos), the local mechanic was gushing specifically, about how great the carbureted version is. As far as I can tell, if you adjust it per the manual (balance the carbs), and not run old gummy gas, it works just like fuel injection. At least that has been my experience. I bought the motor on a '98 Alert/Montauk in early 2011 with 800+ hours on it. Shamefully, I've only put another 100 hours on it since then, (four other boats, (one another Whaler), two small girls who need their papa's attention, etc...), but I'm very satisfied with this motor and so far, I'm glad it's carbureted and not fuel injected, as I can perform the tuning steps myself.

But all is not sweetness and light in "FourStroke'ville". This motor is BIG. And more importantly, HEAVY. My finely calibrated instrument, (seat of the pants), agrees with the historical fact that the classic hulls were not designed for such weight on the transom. This hull was designed in the era of light and powerful, carbureted two-stroke-cycle outboards.

A bit of trivia that would be easy for Jim to have missed: I get this motor serviced at a Yamaha dealer, by a Yamaha mechanic. The mechanic insists the powerhead is a Yamaha F100. In other words, Yamaha sells this same motor as a 100hp. Which explains why it is so strong as a 90hp.

-Peter

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Phil T
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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby Phil T » Thu Aug 03, 2017 2:19 pm

Many members refer to your version as the Mercaha 90 or the Yamacury 90.
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jimh
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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby jimh » Thu Aug 03, 2017 9:01 pm

Having owned a 225-HP engine with SIX carburetors, I can also say I never had a bit of trouble with the carburetors. And I don't think there is anything intrinsic in very simple electrically controlled single point fuel induction that makes for a wonderful improvement over carburetors--as long as you are not trying to start the engine when the ambient temperature is about 10-degrees-F. For most boats, the engine is run at close to sea level or maybe a few hundred feet above sea level, and the ambient temperatures are very moderate, about 65 to 85 degrees. A carburetor works very well in that environment, and engines can start very quickly and run very smoothly with carburetors.

But there are many long threads about Mercury 90 FOURSTOKE engines with carburetors having problems with the carburetors. Quite humorously, the blame for these problems by ardent defenders of Mercury is laid on the shoulders of Yamaha for their lousy carburetors.

To me the most important improvement in simple electrically controlled fuel induction compared to carburetors is the elimination of an open vent to the atmosphere in the carburetor that allows fuel to evaporate. Boat engines sit for long periods of non-use and when all the fuel evaporates from the carburetors the residue left behind can be a problem. That is likely what caused the problems for the Mercury 90 FOURSTROKE with carburetors. And, as mentioned, probably some lousy gasoline fuel helped create problems, too.

But this is all a topic for another thread, as this thread just tries to help identify the several manufacturing epochs of Mercury engines that have all been give the same model name: 90 FOURSTROKE. The mission of this thread is to aid in distinguishing one 90 FOURSTROKE from another 90 FOURSTROKE, which, despite the identical model names, are radically different engines.

pcrussell50
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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby pcrussell50 » Thu Aug 03, 2017 10:16 pm

jimh wrote:But this is all a topic for another thread, as this thread just tries to help identify the several manufacturing epochs of Mercury engines that have all been give the same model name: 90 FOURSTROKE. The mission of this thread is to aid in distinguishing one 90 FOURSTROKE from another 90 FOURSTROKE, which, despite the identical model names, are radically different engines.


True, Jim. More on topic and my more focused point was that the carbureted Mercury 90hp FourStroke powerhead is actually a "100 horsepower", Yamaha F100. Both according to my Yamaha mechanic, and based on the fact that I order parts for it from the Yamaha parts suppliers.

-Peter

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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby jimh » Thu Aug 03, 2017 10:30 pm

I have noticed that Yamaha often sells their engines into the European market as 100-HP engines and sells the same engine into the USA market as a 90-HP, but I don't see that the higher rating for the Euro-boaters means that the engine really makes 100-HP. It might have 95-HP and be a more accepted in Europe as a 100-HP rating and as a 90-HP in the USA.

I suppose the ultimate authority would be:

--the EPA test certificate that rates the engine in kW power for emissions, or

--the dock talk lead by guys who love black engines and insist they always make power power than their cowling decal.

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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby Saukit » Sun Aug 06, 2017 12:57 pm

Hi all--I believe I have one of the second generation "Mercaha" outboards and I thought I'd post a few pictures for reference. I acquired the boat (1992 16 SL) and motor in April of 2016 and to the best of my knowledge the engine is a 2006.
Mercury90-1.jpg
Mercury90-1.jpg (32.9 KiB) Viewed 13414 times


Mercury90-3.jpg
Mercury90-3.jpg (26.93 KiB) Viewed 13414 times


Mercury90-2.jpg
Mercury90-2.jpg (17.44 KiB) Viewed 13402 times

jimh
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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby jimh » Mon Aug 07, 2017 10:28 am

Thanks for the images of the Mercury 90 FOURSTROKE EFI engine c.2006. The marking on the front face of the cowling with "EFI" confirms that there are such engines, although I still think they are uncommon.

[I downloaded your original images. Then I rotated the images to correct for the original camera being held sideways. Then I blurred some distractions in the background and cropped the images. Then I edited you initial article, deleting the original sideways-images, and uploading the new images I made from your originals. Digital images taken with the camera held sideways will not be oriented correctly when viewed as in-line HTML images, as no current browsers support the image orientation tag, except for the iPhone version of Safari. When taking images that may be later used as in-line HTML images, it is best to hold the camera with the proper orientation.]

Saukit
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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby Saukit » Mon Aug 07, 2017 8:45 pm

Thanks for fixing the pictures Jim, they were taken on my phone. Next time I will take them in landscape format instead of portrait.

I imported this boat and motor from BC, Canada. When I brought it back I assumed the engine was an American version that had been taken up to Canada. Maybe that is not the case and this was a Canadian model? I was given the manual and it doesn't seem to be any different than the ones available online. It was no problem to import the engine and the Border Patrol didn't give me any reason to believe that it wasn't a US engine.

Either way I appreciate the time you have put into researching the different iterations of this engine. It has certainly been illuminating for me.

Brett

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Dutchman
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Re: A Brief History of the Mercury 90-HP FOURSTROKE

Postby Dutchman » Tue Aug 08, 2017 1:03 pm

Saukit wrote:Thanks for fixing the pictures Jim, they were taken on my phone. Next time I will take them in landscape format instead of portrait. Brett


Brett don't worry you and too many others hold their phones in correctly when taking video (or pictures) see this Public Service Announcement
https://www.youtube.com/watch?v=Bt9zSfinwFA
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