poor gas mileage ?

[double_trouble]

I am runnning an 19' wellcraft cuddy cabin powered by an mercruiser 170hp. My gas mileage has been terrible. I will generally go through 1/2 to 3/4 of a tank fishing in 3-4 hours. I do not have a long run to start fishing nor do i troll great distances. Is this normal for this engine? I was wondering if rebuilding the carb would help improve it at all?

ANY IDEAS?

more info that may help:

The boat is a 1986 Wellcraft American 19' Cuddy, not sure of the weight but I know it is HEAVY. IT has a two barrel carb on it and it has the enclosed cooling system with the heat exchanger. at idle it purrs at 650-700 rpm no problem. at WOT it runs around 4000 rpm. I usually run it 1/2 to 3/4 throttle going in and out and when i troll it is running around 900 to 1000 rpm. I am not sure the pitch and size of the prop the boat was new to me last year. it also has the STINGRAY on it to help it plane easier.

[Shellback]

I would look to the ignition system and tune up specs first. A simple thing like ignition timing could greatly effect your gas consumption. Another thing to check is the carb choke to make sure it is opening fully when warmed up.

[L&M]

Trouble: I've seen this posted by you on some other sites as well. #1 4000 rpm's at WOT would indicate wrong pitch prop of which makes the engine work harder. IE. more fuel consumption. Engine should turn 42 to 44 hundred wide open or up to 45 or so with one person and full fuel. Not sure, but I'll look in to what capacity tank is in that particular boat as well. #2 The replies you got over there are valid for the most part. There are a lot of variables such as choke, carb, state of tune, compression and general cond. the engine is in. Hope that helps. Any questions or help you need let me know. 165, 170's or 470's basically the same motor they are usually pretty good on fuel consumption if all is well. All tho they did have there problem's as any other engine does.

[UpGrady]

I have twin 170's in mine pushing a 25 Grady (a good 8000 lbs with a full tank of gas(125gal)). By the flow meters and gas bills... I push about 7gph thru each cruising at 3500 rpm. Wide open, with the correct prop you should get close to 4400rpm. At trolling speeds, you should not push thru more than about 1 gph in the engine. So, if you head offshore 1/2 hr out/ 1/2 hr back in and troll for eight hours, you should not be burning much more than 15 gallons of gas. Electronic ignitions really helped the engine performance as well.

[double_trouble]

What exactly is involved in switching this unit over to electronic ignition?