Spring tune-ups check Fuel System

Greetings CCFans

It’s almost that time year for de-winterization and Spring tune-ups. Last year this time I was very frustrated trying to figure out what was wrong with my boat. I want to post my experience because there maybe someone out there this year struggling with the same issue.
My boat is a 1977 Ski Nautique with a 351 Ford. The symptoms I was dealing with were rough starting, rough idling, hesitation, bogging during acceleration, engine cutting out at cruising speed and a general loss of power.

At the beginning of my quest I didn’t really know where to start. Since I’m not a professional mechanic, I started with all the easy stuff like running out the old gas and replacing it with fresh ethanol free gas, trying to drive any water out of the fuel system with Iso-Heet, putting in a new battery, putting in new spark plugs, changing the air filter, oil, etc. None of these solved my problem.

The more I thought about my problem, I was taking myself in the direction of it being a problem with my carburetor. This is where I almost threw in the towel and took my boat to a real mechanic. But last time I did that (a few years back), I was shocked with a big repair bill and came the conclusion that it’s hard to find people who really know inboards (at least within reasonable driving distance for towing a boat). So, I decided that I would figure this problem out myself even if it meant taking things apart and going into uncharted mechanical territory for me.

Ok, so I’m going to spare you of the many frustrating dead ends that I encountered and cut right to the chase. My problem described above was centered on one key issue. Over the years (since the last major overhaul of my boat in the 90’s), many of the rubber components in my fuel system had deteriorated. Whether this happened from exposure to ethanol in the gas or just age, I don’t know, but what I learned is the rubber components were a common thread between all my issues. One I began replacing components in my fuel system, the symptoms improved.

Fuel pump: the first clear diagnosis I was able to make was the rubber diaphragm in my fuel pump was barely putting out any fuel pressure. The fuel pump of all things on an inboard engine is actually not very hard to replace. It is easily accessible (at least on my boat) and it comes off by releasing a couple hoses and three bolts. Immediately with the new fuel pump, my problem of rough starting and engine cutting out went away.

Fuel line and filter: after replacing the fuel pump, I decided that I should take a look at the fuel line running from the tank in the rear up to my fuel pump. It didn’t look too bad close to my engine but all the way back by the tank I could see that it was showing signs of age. So I replaced the fuel line from front to back with a new ethanol resistant line. The lines going between my fuel filter and pump are metal, so I didn’t have to replace those. At this time, I also replaced the fuel filter. But with these improvements in place, not all problems were solved. I was still dealing with the rough idling, hesitation and loss of power.

Carburetor: as I was running the boat and trying to figure this out, I realized that I was getting some persistent drips of fuel from the bottom of the carb bowls, mostly on the primary bowl side. I hardly noticed these drips until I started looking more closely because the fuel was mostly evaporating when it the warm surface of the engine. But, it started to make sense when I realized this might be the reason the paint was flaking on the top of my engine near the carb. This is the point when I decided that (1) I needed to try either installing a new carb or (2) try to rebuilding my carb. The first option turned out to be about $400-$500, so I decided to go with the second option of rebuilding the carb where the kit cost about $75. Finding the rebuild kit for the original carb on a 1977 marine engine wasn’t the easiest thing, but I eventually found it at www.carbkitsource.com. I replaced all of the seals and valves that came with the kit. And, I cleaned-up all the components real nice with carb cleaner and compressed air.

Moral of the story: after all of these fixes, my boat ran flawlessly for the rest of the Summer. If you are experiencing any of the symptoms that I mentioned above, I would seriously try investigating what rubber components in your fuel system might be failing. In terms of preventative maintenance, I now run exclusively ethanol free gas with 2 ounces of Sea Foam (which is petroleum based) in each tank. I find that Sea Foam works for driving small amounts of water out of the gas if used regularly. It doesn’t work nearly as well as Iso-Heet for driving water out of the gas, but I now hesitate putting any alcohol based product in my gas because my theory is that ethanol and isopropyl are two major culprits for drying out the rubber components in the fuel system. Modern automobile fuel systems don’t have this problem because all of the rubber components have been upgraded to be ethanol resistant. Note: I don't normally get water in my gas but I just try to stay on top of it is bound to happen with condensation in the marine environment.

I hope someone out there finds this helpful. Happy boating!!! Please feel free to let me know if you have any questions. I’d be happy to take questions regarding this experience because in about a month I will likely be on this forum asking questions about how to troubleshoot and replace a starter motor.

I have the opposite problem have the boat 4 yrs and it never missed a beat.Last year pulled the plugs and looked under the cap everything looked great.Never s hint of hesitation rare for a Quadrajet but careful inspection looks like its never been apart but not likely after 29 yrs.Change fluids and if it ain't broke don't fix it.

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