75 hp Tracker by Mercury (1997)

[MurphyMax]

I bought a 97' Sun Tracker 25' pontoon boat with the original 97' "Tracker by Mercury" 75 hp O/B 2stroke(-). The motor seems to run okay, but fuel consumption seems high to me. (1) Is this really a Mercury motor or an offbrand- make? (2) What fuel economy should I expect? (3) How fast should a 75 hp push this big pontoon at WOT? (4) It was idling rough, so I replaced the 3 plugs, which showed a lot of oil fouling -- Is this normal for this 2stroke-? (5) Occasionally it backfires slightly when re-starting cold -- What could cause this? (6) The tachometer is wildly erratic -- is this likely just a defective tach, or is this a defective engine sender? Sorry to blast you guys with all these dumb questions, but I'm' new to outboards!

[ricksrster]

What are your RPM at WOT?
The tach send wir is connected to the rectfier on one of the posts with the wires from the stator.
You might need to link and sync.

[Silvertip]

1) It is a Mercury engine. 2) It will burn roughtly 7.5 gallons/hour at wide open throttle. Possibly more or less depending on if it has a proper prop. You are pushing a big load through the water so it will not be an economy champ. 3) What type of plugs are you using.? If you spend much of the time at slow speeds you will be better off using conventional plugs rather then the surface gap. 4) If the engine sneezes on restart the idle mixture may be a tad lean. 5) There is an adjustable dial on the back of the tach. It should be set on "6". Turn the dial back and forth a time or two and reset at "6". Check and tighten the 12V, ground and sense, wires on the back of the tach. 6) No idea on speed. It depends on the prop, weight, load, size of pontoon, etc. Prop it for 5250 - 5500 RPM. What you get for speed is what you get! Use a pontoon prop (large blade area)