By Preston Larus
About three years ago, my wife and I decided that what we needed was a small, plain, low-maintenance boat that would fit in the garage and be easy to use with minimal tinkering to distract us from, well, jobs. We came to this conclusion after the sting faded from selling our larger, classic-looking, high-maintenance boat at a substantial loss. Memory is selective.
I had heard great things about the ride quality of the Scout hull design, so when a 1991 14-footer appeared in the classifieds, we went to see it. Well, it was about as sexy as a Croc (those trendy plastic shoes), but we were going for function over form this time. The 30-horse Yamaha 2-stroke was clean as a whistle and the whole rig was in great shape for its age. We had all but consummated the sale except for the test ride.
There was a problem. When throttle was applied to accelerate, it would bog down and would not quite get up on plane. If you shifted your weight far enough forward, it would finally get over the hump and take off. The seller suggested this was normal, and if I was in my 80s like he was, I might have agreed, but I knew that a 30 hp outboard should not be that anemic in terms of low-end torque. I bought it anyway with the confidence (or hubris) that though this was not right, it could be fixed – and we really wanted that model of Scout and they are kind of scarce.
Despite his claim that this was normal, after the sale was complete, the seller produced his notes regarding the very same problem. It seems that a few years back, he let the boat sit a long time and the gas went sour and gummed up the carb. He had it professionally rebuilt at the Yamaha dealership but it was never right after that, despite several visits back to the “Service” Department.
I had a go at it and couldn’t find anything obviously wrong. After some messing around, I couldn’t even decide if the problem was fuel-related or ignition-related. Two mechanics had a go at it (each one going through the carburetor carefully) and $150 later, it still was the same. We all agreed by now it was fuel-related but … was it getting too much? Or too little?
In searching the Internet for clues, I happened upon the self-appointed “Master Tech” Bill Kelly, who offers a ton of excellent resources at his site (www.maxrules.com) – troubleshooting tips, service manuals, parts, and what-all. (Bill’s troubleshooting rules: 1. Proceed logically! 2. Believe your evidence! 3. Never assume anything, EVER! 4. Check EVERYTHING, you could have multiple faults!)
And if all that doesn’t help, you can pay $20, send an e-mail describing the problem, and Bill himself will call you (from Hawaii, at that time) and steer you toward a solution. Desperation eventually overcame skepticism, and besides, I had already spent considerably more on the local talent to NOT fix it so far. I paid my money and took my chances.
The Master Tech earned his $20 and my respect. His troubleshooting technique was elemental and brilliant and proved to be the key to the mystery. He suggested this:
Test 1: Remove the engine hood and the air cleaner housing. Accelerate as normal, and while it’s laboring to get on top of the water, direct propane into the carb throat from an UNLIT propane torch and see if the engine speeds up and takes off. That addition of combustible fuel solving the problem for a few moments would indicate fuel starvation was the problem.
Test 2: If Test 1 yields no clues, again accelerate as normal and unplug the fuel line from the engine. If, as the carburetor runs dry (and the fuel mixture leans out just before the engine quits), you get a burst of power and RPMs, that would indicate that the problem is too much fuel.
Test 1 produced no change. Test 2 made it run like the devil for a second or two. Whoulda thunk it? Too much fuel!
But what to do about it? How to isolate the cause of the trouble?
I called Mechanic #1 (who had already had a go at it) and updated him on the Master Tech’s analysis. Coincidentally, he had another 30 hp Yamaha in his shop at that time, and agreed to use it as a diagnostic benchmarking tool, meaning he swiped the carb off of it for a few hours, met me down at the boat ramp, and put it on my engine.
My boat ran perfectly, for the first time since I’d owned it (several weeks by now!) – smooth, powerful, quick to plane.
Next, he removed the other customer’s carb, removed its main fuel jet, put that in my carb, and put my carb back on my engine. Again, perfect performance. He put the other customer’s fuel jet back in his carb and put it aside so he could restore the customer’s engine to pre-diagnostic condition back at the shop.
Next he returned to my carburetor. A main jet is nothing more than a finely machined brass ferrule a little larger than a pea (careful, butterfingers) which threads into the main body of the carburetor. It has a precisely-sized opening in the center (measured in thousandths of an inch), which admits just the right quantity of gasoline into the air stream as the engine sucks it in. Somehow, my main jet was too large – even though the markings indicating the jet size were identical to those of the other carb.
I was a car mechanic in the early 80s when there were plenty of carburetors still around on the MGs and Fiats I worked on, and the essentials of a carburetor overhaul were to completely disassemble the carb, put the carburetor body and all metal parts into a basket, and lower the basket into a bucket of carburetor cleaner, where it would sit overnight. Next day, you pull out the basket, rinse the parts with water, and then use compressed air to blow out all the passages in the carburetor body and dry all the parts. Then, you reassemble the carburetor just so, using new gaskets and other parts as might be supplied in the rebuild kit and following the instructions very carefully.
If this sounds like a pain, consider that it was way better than purchasing a replacement carburetor. You could get a complete overhaul kit for 20 bucks when a replacement carburetor could run hundreds. Nowadays, carburetors are so complicated they don’t even bother to sell the kits, and prices of new ones can run over $500.
Which, by the way, gasoline ain’t what it used to be, either. When I was a kid in the 60s and early 70s, our outboards would sit all winter while we were in school and fire right up the first day of summer and run right until the end of vacation – gumming up wasn’t a problem, and no one seemed to need fuel stabilizer. Now, I’m afraid the gas might gum up in a month or two, so after I flush the engine with fresh water I unplug the fuel line to let the carbs run dry before putting the boat up. Never know if I’ll be back in a few days or, if work gets busy, it might be a few months and I don’t want to have to overhaul the carb. Now that I think about it, we never flushed the salt water out of our engines in the old days either, and they never seemed to suffer.
Anyway, the carburetor cleaner dip was essential to the rebuild process, since foreign objects like dirt and gummed-up gasoline are the primary causes of most carburetor trouble in the first place (the secondary cause being the failure of the non-metal parts like gaskets, seals, and rubber diaphragms and such which come in the kit and get replaced routinely anyhow, and the tertiary cause being corrosion of the pot-metal carburetor body caused by moisture in the fuel – this last malady usually didn’t stay fixed for long after the rebuild, as the corrosion continued to flake off over time and plug up vital passages). The carburetor cleaner is a mild acid, but not so mild if it gets on your skin, as I found out once when I dropped a small part into the barrel and fished it out with my unprotected hand. No harm done, but it hurt and I had an angry rash for a few days right up to the high-water mark near my elbow.
But back to the mystery at hand. It seems that the Yamaha service literature says not to soak Yamaha carburetor bodies in the stuff – something about a special coating on the metal that will be removed by the acid bath. So we theorized that the original Yamaha technician at the dealership, facing a gummed-up carb and no other way to get the deposits out of the main jet, had elected to use some sort of tool to clean the main jet and in doing so, actually reamed it out to a larger size.
The mystery was solved, but I still had a carburetor in need of a replacement jet. The dealer informed me that, though it was only a $5 item, there did not seem to be a main jet in this country and that getting one in from Japan could take 6 weeks – a long time to be without a boat. I got on the Internet, found a used carburetor, and had it in my hand 2 days later. I swiped the jet out of it and have had a great-running engine ever since.
I forgot to cancel the jet order, so six weeks later, the jet and float bowl gasket arrived and I still have them, just in case … just in case of what, I’m not sure. Maybe I can sell them to a Yamaha technician.
This would be a good place to end this article, but while we’re on the subject of puzzlers (puzzlahs, as they say on Car Talk), this boat presented us another goody a year or so later … I had bought a spare fuel tank from the local chain marine store – Tempo, 3 gallons, plastic, $18, and with that engine, good for a few hours of running time. A bargain at twice the price.
That weekend, we trailered the boat about 90 minutes south to Pine Island, Florida, which sits at the southern end of Charlotte Harbor. This is a little south of famous Boca Grande Inlet, tarpon fishing capitol of the world (in season, the overpowered, overloaded fishing boats are gunwale-to-gunwale out there – dangerous business). A little south, almost to Fort Myers, are Sanibel and Captiva Islands, tourist destinations for well-to-do people from all over.
Our destination was Cabbage Key on the Intracoastal Waterway, where there is a bar, restaurant and inn accessible only by boat. You may have heard of this as the place that is wallpapered in dollar bills, which customers are encouraged to write witty (sometimes not-so-witty) things on and then stick on the wall. I think they said there were 40,000 dollars on the wall, but who’s counting?
Having visited for meals a few times before (good food, too), we had decided to splurge on a weekend getaway and spend a night there, just for the yo-ho-ho of it. So we launched the boat, locked the car and headed out the narrow, rock-lined cut leading from the town (well, post office, sort of) of Pineland. We crossed to Cabbage Key, checked in, had a nice dinner, and got back in the boat for the sunset and a twilight cruise before bedtime.
I switched over to the new tank long before tank # 1 went dry, so as to have a prudent reserve in case I (imprudently) got distracted and allowed tank 2 to run out. We idled around for awhile, but when we went to accelerate, the engine starved (I guessed) and died.
We switched back to the old tank, pumped up the primer bulb, and ran without trouble. Switched to the new (brand-new) tank and again, could not keep the engine running above idle. The primer bulb felt funny … didn’t firm up quite like it did when hooked to the other tank. Hmmm. It was too dark for troubleshooting by now and we were sitting ducks to get run down by a speeding Sea Ray out there in the Intracoastal Waterway, so we limped back to the inn to sleep on the problem.
The next day, my wife wanted to give up and go back to the boat ramp early but I figured it was worth a little troubleshooting to maybe save the day from the mechanical gremlins.
Now, we could have had a bad fuel pump diaphragm or something else not readily available on a Sunday in Pineland, FL, but I figured we’d start with the basics. I disconnected the engine end of the fuel line, removed the disconnect end (never go boating without at least a few tools) from the hose so the check valve wouldn’t interfere with my investigations, and watched the gas flow (into the filler of the tank, not into the bilge) as I squeezed the bulb. The flow was weak and it seemed there were a lot of air bubbles in the gas. Curious.
We disconnected the tank end of the hose from the new (brand new) fuel tank and hooked it to the old tank, squeezed the bulb … strong, bubble-free spurt with every squeeze of the primer bulb. Hmmm.
Nothing to do but see if there was something funny about that new (brand new) tank. The fuel line fitting threaded into the top of the tank, so I unscrewed it and it came out with the fuel pickup attached. So far so good.
The fuel pickup was nothing more than a length of hard, translucent plastic tubing long enough to reach about a half-inch from the bottom of the tank. It was attached to the nipple on the underside of the fuel line fitting by a force fit. In this case, the fit was a bit too forced, as the pickup tube was neatly split where it fit onto the nipple, and this prevented the suction of the primer bulb from picking up enough gas. I robbed the fitting from the old tank and put it on the new tank and off we went for a lovely day of messing about, made all the sweeter by my masterful (and modest) problem-solving.
You know, troubleshooting is gratifying when you win, frustrating when you lose. My wife has seen enough of the latter that you really can’t blame her for wanting to give up and go home. It can get ugly. As I tell my teenager, hell, I wasn’t born this smart – I’ve screwed up so much over the years, it was inevitable that I eventually learn something. This day, though, I was The Smartest Man Alive. Ask my wife.
The following Monday, the guy at the marine store apologetically exchanged the new (brand new) tank for a replacement. Wise Master Tech say: Assume NOTHING … so I checked the fuel pickup in the new (brand new) tank right there before leaving the store.
Go thou and do likewise.