By Tom Neale, 11/29/2007
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Mystery in the Mako, Tom in a mess
Of course, he’d checked the fuel filters. And he’d replaced the fuel lift pump. And he’d traced his fuel line and entire fuel supply system for kinks, air leaks or other gremlins. He’d even pulled his fuel pick up from the tank and checked it for stoppage or blockage at that end. It was free. And then he had the joy of bleeding the whole fuel system to get all the air out, which he’d already tried early on, thinking there was air in the system. The only thing he hadn’t done was pump out the tank and look around down there through the three inch “inspection port”. And this, he clearly didn’t want to do.
Joe (yes, it’s a fictitious name,) was proud of his old center console and its outboard. He’d bought it cheap and fixed it up until it was a gem. It was an old tough hull and, although the motor was a fuel burner, it had been performing perfectly. Had been. In the past three weeks he’d replaced all spark plug leads, the plug power packs, the safety kill switches and various other components. He’d spend hours and hours and dollars and dollars. Because the perfect performance had changed. He’d be zipping along, hit a wave, even a small one, and the engine would sputter and briefly loose some of its power, sometimes almost instantly, sometimes after a very brief interlude. Occasionally it would shut down altogether. Then it would run fine until he hit another wave and the same thing would happen—sometimes. He figured it had to be something electric. He surmised that when the rig was jarred it knocked loose a connection or a bad wire splice or whatever. So his engine was like brand new, electrically speaking. But it still had the problem. Then he checked out other theories. Somebody theorized that there may be an unseen break in the positive electrode within the insulating jacked of a spark plug and that when the boat was “jiggled” there was a temporary disconnect in the plug. He replaced them all. Someone told him that the float valve in the carburetor was hanging up when the boat was jarred. This theory really didn’t make sense, but he pulled his carb and rebuilt it anyway. Someone said, “maybe there’s something wrong with your fuel filter.” He checked. It wasn’t. And the irksome behavior didn’t stop.
Around a month ago, I was running my 1985 twenty foot Mako up the Rappahannock River, having come around Sting Ray Point out in the Chesapeake Bay. It was a beautiful day and the engine was running like a charm—not bad for an outboard over 20 years old. The boat had had two previous owners, and, like the guy above, I’d bought her cheap and had spent lots of blood sweat and tears (not to mention quite a few bucks) to bring her and the engine up to prime again. Smiling, I was thinking, “Ah, it can’t get any better than this.” The loud whine of an alarm booted the thought from my mind. Alarm? What Alarm. Everything’s fine. I check the cooling stream every few minutes when I’m running. I’d just serviced the engine. I was hoping it was a hallucination. But it wasn’t. What it was, was the low oil alarm. The Yamaha was a two stroke, with oil injection. You’re probably familiar with the configuration. A large oil storage tank resided down in the hull. An oil pump was attached. A smaller storage tank was affixed to the engine under the cowling. From this tank the injector pump withdrew the necessary amount of oil to mix into the gas. A sensor in that tank told the motor on the large tank to pump oil up through a tube to keep the small tank full. A sensor in that small tank and the large tank sounded the alarm any time the oil level got to low.
“Impossible,” I numbly thought, as I shut down the engine. I just filled the big tank. I looked into it and it was full. I pulled the cowling and, sure enough the oil level in that tank was down to the “low” line. It still had a ways to go before any harm would be done, but the system was telling me that trouble was ahead if I didn’t take corrective action. I took all the corrective action I could as the wind came up and the waves started kicking us around. Nothing worked, so finally, using a spare outboard motor fuel line with priming bulb that I keep around for situations like this, I pumped up oil from the big tank into the smaller one and this gave us enough safe supply to get back to the dock.
I dug into the problem further, and pulled the main oil tank out of the boat. The pump was working fine. The oil filter seemed OK. Carefully, I poured all the oil from the tank into clean containers and looked into the bottom of the tank. VOILA!
Diagnosing engine problems
Flashes of light from within. Floating around in the small amount of oil left. I reached in with a “grabber” and pulled one out. It was a piece of aluminum foil. Torn from the top of an oil jug sometime in the dark past of previous owners. You know them. Every time you (or a mechanic) opens a well packaged plastic jug of oil, fuel additive, or lots of other things, you’re blocked by that aluminum protective seal covering the top. I don’t know how they fix it there, whether its glued, heat sealed or what, but I know it’s usually well fixed there. So you’re standing there, wanting to pour in the product, your hands are probably covered with slippery oil, and you need to get rid of that seal. You probably don’t want to reach into your pocket with your dirty hands and get a knife to carefully cut and peel away the seal and you’re in too much of a hurry to go rustle up a screwdriver to neatly break the seal. Instead, you use a fingernail and punch through the aluminum. You try to pull it off, but it’s already partly down in the opening hanging by one side, and your fingers are even more slippery now. So you push it down against the side and start pouring. All to often, during the pour, the flow breaks free the seal and it—or a part of it—goes into the tank. Most of the time you don’t even know it.
In each of the stories above, that was the problem. The guy with the diesel eventually found that a multitude of seals were sloshing around in the bottom of his tank, and sometimes one would clog up the end of the pickup tube. When suction ceased (as when the engine was off) it would drift free. The guy with the intermittently running outboard, found the same thing. Sometimes a jar from a wave would slosh the gas around in the tank and an aluminum seal that had once protected a bottle of fuel additives got sucked against the pickup tube. The screen over the end of the tube allowed some gas through, but not enough. At the bottom of the oil tank in my Mako I found only one seal, but it was stuffed into the orifice for the oil line and it had been enough to do the deed.
Copyright 2004-2008 Tom Neale