REPAIR: 4 Pack Carb Rebuild

[adudinsk]

My Merc 75HP carburetor outboard was sputtering a bit.. did not worry too much.
Then weeks ago, we planned to go away for the weekend.
Motor would not start at all.
Dead... No start...
But the other day it ran ok enough.

After testing everything/ fixing the charge system/ replacing a dead Throttle Position Sensor (TPS) it was still dead.
Last thing I wanted was to rebuild a 4 pack of carbs.

But alas.. they needed it.
After removing the intake manifold and air intakes.. and throttle linkage... it was not a big deal.
When I opened up the carbs..2 had jets plugged solid.
and the gaskets on the upper cover were all covered in debris. I sent photos to Merc. and they said "100% from long term use of ethanol based gas, or the use of SeaFoam" (Contains Alcohol.. very bad.. ok in old 2 stroke lead based engines.. but not now adays)

So avoid seafoam for modern engines at all costs..
ONLY buy super unleaded *(no ethanol or "engine cleaning" additives).
Make sure your go to a reputable gas station, as some around here (Detroit bridge Duty Free Gas) did sell regular as Super 93 octane...

Rebuild was actually fun..
Got lots of "street cred" at the Yacht Club.
Dealer wanted to just sell me a Suzuki.. as my engine "was old and hard to get parts for.."
Fixed the carbs for about $400 us in rebuld kits..
Learning how to rebuild carbs.. priceless..
Telling the dealer "no.. it was easy .. got it working" .. beyond priceless..

So in short look at the photo.. DO NOT use seafoam. (has isopropyl alcohol... and lots of it..)
Use the Mercury 3 part system.. or Yamaha has a great product.. Just look up active ingredients.. and make sure it has no Alcohol.

[Jimmyt]

Great job!

[Dougiestyle]

NO ETHANOL bad for boat motors!!! Good job.

[adudinsk]

I was just surprised that seafoam had lots of alcohol in it. If you actually followed the "flush" procedure, and used 50/50 and soaked it.. not the greatest thing to do. I guess a one off is not "bad" but there are MANY better carb cleaning processes, so never put seafoam in every tank as a preventative. If so you get this kind of build up over time. I only use 93 octane/ no alcohol. Just got the boat last year.

Now need to order a set of Carb Synchronization gauges.. maybe build my own via an arduino... as per many online plans.. (depending on price)


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[Interim]

How does Seafoam cause a problem? Does the alcohol attract dirt and grime?

--john

[Jimmyt]

Not going to get into the Seafoam discussion, but alcohol in general, is bad. My bad experience involves engines that don't have rapid fuel turnover - including late model cars designed to run on ethanol blended gas. The alcohol attracts water, then forms all sorts of fun stuff and eats parts, corrodes, and causes general havoc. Carburetors, fuel tanks, including in-tank fuel pumps and fuel gage sender, are the primary damage areas I've seen. Now, I live in a very humid area, which could be a contributing factor. But, I will not put anything but non-ethanol gas in my small engines (including my outboards). In my Mac, my Etec 60 might go through 6-9 gallons per season. After that, I run it in my lawn mower and put fresh in next season.

I do run ethanol gas in my daily drivers. I think it's ok if you keep it turned over frequently.

[adudinsk]

Agreed.. alcohol for daily drive is ok... fast turn over..

And your not in the water.. less chance of it absorbing h2o

Most cars now are designed for a % of alcohol... gas tanks are air tight and sealed under positive pressure.

Only problem with alcohol in daily driver is that it condenses and that is Very acidic.. and can damage exhausts that are not stainless steel... over time.

As well if you run alcohol.. it is less power output than pure gas.. so if you ran a car in 100% alcohol (some can) you get way less mpg.. and power..
But it is cheaper... so the overall cost per mile driven is about the same.

The benefit was it keeps $$$ in the country.. farmers employed to make corn to produce the alcohol.. not buying petrol / oil from another country.

Also with alcohol it may cause SOME high compression car engines to knock.. (ie: BMW/Porsche..etc)

Top Shelf fuel is another format that is now being required in newer (high end) cars (direct inject engines especially) as it has detergents in it to prevent carbon build up (costco gas is top shelf certified), as the fuel does not flow past the valves.. but rather is injected directly into the combustion chamber... this intake valves carbon up easier.

Chrysler has a TSB that said once a week to rev your 3.5LV6 to 4500 rpm for 45 sec to "knock off" build up... (good engine design guys... not..)

And lastly, not all outboards are "new".. so considerations for alcohol in gas was not thought of much..
Having a Mac.. I fill up the tanks at the gas station (not marina) and use high test..92 or higher.. no alcohol..
Not very expensive compared to a marina... better be safe than sorry.

And yes.. everyone has their fav. fuel additive.. but fuel injected engines should never need it.. unless neglected.

AD

[Interim]

Thanks. I've been using the high grade (non ethanol) fuel in my yamaha four stroke for years, but didn't realize I was reintroducing the problem with my fuel additive.

Progress.

--john

[adudinsk]

One off.. Seafoam is ok..
Eevery tank.. not good.


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