lime4x4 said:
Anyone have an idea how much fuel twin 1987 150 2 strokes burns? I know fuel gauges are a never accurate. But it seems everytime i take the boat to the local lake it uses a 1/4 tank of fuel according to the gauge. I generally run the boat at 4K for about 15 min then i'm putting along at 1K for another 15 min. I've tried filling the tank and refilling after using it but that doesn't seem to hold out. The other weekend i filled the boat with fuel. I stopped when fuel started spitting out the vent. Went to the local lake when i was done i filled the boat back up and it took 21 gallons of fuel. I know the older 2 strokes aren't exactly fuel effeint but using over 20 gallons of fuel in 30 minutes seems kinda high. I have 30 foot cabin cruiser with a single carbed 350 vortec engine that gets better fuel economy
Those motors usually will use 10 to 12 GPH at those revs, so 20-25 GPH for two motors. !5 minutes should burn off about 5 gallons. Consumption at 1000 revs should be much lower.
How does your exhaust look? Black perhaps? I suspect that you are running rich on one or both motors. Are your motors carbed?
Also look at the water for a fuel sheen just in case you are dumping fuel out the exhaust.
If you are running real rich, your plugs should be fairly black with carbon after a relatively short usage period. You might want to pull the plugs and see how they look and if all look similar.
If the motor is injected ( I dont think the 150s were injected in those years) there are other things to check.
The funny thing is that it is possible that the fuel consumption is way up at low revs especially if carbed and the needle valve doesn't close or the float is bad or mis-adusted. If you troll you will burn rich but if you rev up to return you can burn off the carbon from the plugs and not know what is going on. You should see excessive smoke at low speeds if that is the case.