posted 08-17-2012 01:50 PM ET (US)        

--for some, they never have a problem at all;

--for others, they let old fuel sit too long, get the carburetorss cleaned, and it works fine again until they let it sit too long--at least it's a predictable thing that happens to all carburetor outboard engines and yard tools;

--the most unfortunate group develop problems early, and a thorough carburetor cleaning only works for a VERY short time, and it happens repeatedly.

It is the third group I am referencing, and from fishing needles out of the various thread haystackes here I have come up with what I think may be the cause for the problems plaguing group three.

I believe these carburetors have a protective coating on their insides, that when compromised, allows phase-separated ethanol or the water drawn in by such to corrode the aluminum. At this point in the fuel system, all the filtering in the world is worthless, because the there are no more filters between the fuel and the tiny jets and orifices. So a cleaning gets rid of the debris--for a short time--and then it happens all over again.

The handful of marine technicians, that have a true understanding of this problem, end up replacing the pitted float bowls. These are only $170 each and four are required. In the worst case, the carburetor body itself needs replacing. The trouble is, those are nominally $600 each, and there are four of those. Not very happy news overall for group three. Just a theory as to why.

posted 08-18-2012 10:14 AM ET (US)            

Good luck with that Mako. Some later model Makos have had some problems you may wish to learn about preparatory to your purchase. I believe there is a Mako owners site. A search on THT may also be helpful.

posted 08-18-2012 02:36 PM ET (US)            

1) one owner, (referenced by Jim), who managed to exchange his carbureted Mercury FourStroke, for a fuel injected one.

2) Newtauk, who is getting a Mako (an outboard brand I have not heard of). He never did say what became of his particular carbureted Mercury FourStroke. Newt, was your carbureted FourStroke a 70, 90, or 115?

3) I KNOW there were more of you who owned these. What became of your motor? Or are you still using it?

posted 08-18-2012 05:00 PM ET (US)            

BTW, is there some inside joke about capitalization of model names? Mine says FourStroke, yet all over CWW, it's FOURSTROKE. What am I missing?

posted 08-18-2012 07:42 PM ET (US)            

"FourStroke" is how it appears on my cowl and all over my mercury factory service manual. I was thinking the "FOURSTROKE" thing was some kind of joke that Jim has going on with Larry/LHG.

Confused as ever now.

posted 08-18-2012 09:57 PM ET (US)         

pcrussell50, Yamaha , well here ya go:
www.yamahaoutboards.com

check out the dealer in Goleta, CA

posted 08-19-2012 09:07 AM ET (US)            

Later, another 90-HP outboard engine with fuel-injection was introduced, and this was also called a 90-HP FOURSTROKE. This engine was similar to the carburetor engine, but with the fuel induction changed to a simple electronic fuel injection system. The fuel injection may have been something that Mercury worked out themselves and added to the Yamaha engine. These engines are from an epoch when Mercury was still a customer of Yamaha for four-cycle power heads, but this relationship was becoming strained by the investigation started at Mercury's request by the United States International Trade Commission into importation of four-cycle engines made in Japan.

Mercury wanted the USITC to impose a tariff because they claimed their Japanese competitors were selling four-cycle outboards below fair market value. The USITC found that Mercury was one of the largest importers of four-cycle outboard engines made in Japan--all the ones they were buying from Yamaha and others--and that there was no harm being done to the market. The testimony before the USITC showed conclusively that Mercury imported all of their four-cycle outboards or the major components of their four-cycle outboard engines from Japan, except for one 25-HP four-cycle outboard model. That 25-HP engine was the only four-cycle outboard engine made by Mercury in the USA at that time. The archives of the USITC are available on line and reading them will confirm this.

After firing this shot across Yamaha's bow with the USITC charges, the relationship between Yamaha and Mercury became very difficult. Yamaha told Mercury it would not sell them any more four-cycle engines. Mercury had to sue Yamaha in the USA courts to force them to continue to sell Mercury more four-cycle outboard engines made in Japan.

Eventually, a third engine of completely different design based on the VERADO four-cylinder in-line block was introduced and also called a 90-HP FOURSTROKE. This finally broke Mercury's dependence on Yamaha as a supplier of four-cycle outboard engines in this power range. To help distinguish this engine we often call it the VERADITO, a play on the Latin diminuitive of the VERADO, or little VERADO, in recognition of this engine's relationship to the VERADO.

posted 08-19-2012 09:08 AM ET (US)            

So:

1) Always run Stabil (the new blue version).
2) Always run Mercury Quickleen.
3) The carbs are set very lean and are theoretically not adjustable, but after the third season and starting to experience roughness during acceleration and stalling at idle, my mechanic finally drilled out the plugs and set the mixtures to where he thought they should be, undoubtedly losing the 3-star rating, but in the end, it felt like a new engine - perfectly smooth at all speeds - sounds and feels great. He was very hesitant to do this lest the EPA come after him, but clearly they have bigger fish to fry. The ethics and legality of this are left to a separate debate.
4) Added external Racor filter, change filter elements (internal and external) frequently.
5) End of season, every drop of gas drained from entire fuel system.
6) End of season, thorough going-over by above-mentioned serious mechanic.

Anyway, that's my story. After first recognizing the engine could be a problem, I looked into swapping for an EFI version, but it would have been about the same as buying a new engine since there is little used market for the carbed version.

Feel free to ask questions - I'm happy with what I have.

posted 08-21-2012 03:30 AM ET (US)            

Some things I did while ownIng it.
Never went over 2 weeks without running it. Toward the end after I bought my 18, it was a month.
Always ran Quickleen. I did go through a few tanks without and it wasn't as smooth.
Flushed after every use In saltwater.
Used a 10 micron water separating filter.

I remember you saying you tore the carb's apart just to do.
I never did.
Did the problems begin after you did a carb job?

And I wonder the carbs, and needle on a Merc 50 stay clean and clear. If the holes on a 90 are small, the holes on a 50 at small.

Hope it all works outs

posted 08-21-2012 11:38 AM ET (US)            

Threw it all back together and it started instantly. It could use some fine tuning because I have all the needles set at two turns and have not fiddled with them to fine tune. I'll do more fine tuning when I get around to it, but in the mean time it starts instantly and idles pretty well. I worry that that the hard residue that clogged #3 is oxidized aluminum that will return quickly.

posted 08-22-2012 08:58 AM ET (US)            

The mercury was a tiller mounted on a gutted 16'7" hull we use as a skiff. I tried to use the motor often and spent lots of $$$ on new fuel lines and carb rebuild kits. To be honest I hated the motor from the beginning the static trim on the boat was terrible and it lacked the punch of a similar two stroke. The fuel useage was not all that much better than the 3 cylinder yamaha either.

EFI seems to be a must on a mid range four stroke motor in todays fuel supply. Myself I just run what I have and that turned out to be the older technolgy. Starts every time no matter how long it sits.

posted 08-22-2012 02:39 PM ET (US)            

Any others?

Weekend, thank you, too for yours. I still have mine, and it needs some fine tuning after I took the carbs apart and cleaned them. I did a quick sync, but I should spend some more time with that, as well as fine tuning the screw jets, with I have simply set at two turns out, and left there. It's ok, but could be better.

posted 09-04-2012 10:56 PM ET (US)            

On the honda. On my other boat (hydrasports), I have a honda kicker 15hp. I rebuilt that carb 3 times and it still won't start up right. I had to use starting fluid to force it. I couldn't stand it anymore so I bought a new carb. Starts up first shot every single time now. After using it, unplug the fuel line and run the gas out of the motor.
I always used Yamaha ringfree in the main tank. The main motor and the kicker draws its fuel from there.

posted 09-05-2012 02:32 PM ET (US)            

With the garbage (USA) fuels (who knows what) we get today, no wonder they clog up.

I had similar issues with a Honda A/C Generator. That was more critical than the outboard. At least I could get the outboard to run-eventually. NOT so with the gen. set.

I used all the "fuel additives". Nothing seemed to help.

The Honda "Power Equipment" dealers just shrugged their shoulders and said: "ya, they do that".