fuel comsuption

i have a 1987 carver mariner with 2, 350 270 hp crusader engines according to ser no engines are 1986's , my starboard engine burns about 8 gal more fuel than port engine, tanks are a hundred gal each. also all 8 plugs fowl in a short time. choke is manifold mounted and seems to open all the way. spark arrestor is clean. any idea of what to do, plugs have been changed many times , points changed

Ah, the beauty of twins!

Check ignition timing on both engines.... not just BASE advance......, but strobe your balancers and see what the distributors are offering for TA (total advance) at around 3,200/3,400 rpm or so!
More importantly, pay particular attention to where each ignition advance is at your cruising RPM!
Write this down for both engines.
You may need to mark off your balancers if not marked now.

Next, pick up two new base gaskets and swap carburetors from one engine to the other!
Test and see what the results are.

This is nothing more than a P of E..... (process of elimination) .... and you may learn quite a bit from this!
You may have a high speed fuel/air ratio problem, or an ignition spark lead problem.


If it weren't for your plug readings, I'd suggest swapping fuel flow senders from Port/Stbd and see if this also changes anything. You may want to do this anyway if the above proves to show no change.
However, I think that your plug readings play a role in this!

Questions: Are both engines propped identically? Same ratio transmissions?

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Since we are on the subject of fuel consumption. I have a 29 ocean approx 13,000 lbs with twin 350 270 hp crusaders with cuter multiport fuel injection. At 3200- 3400 rpms at 19 knots i am burning 16 gal per hour per engine.. that seems like alot for such a light boat..

thoughts ?

Thanks

Captain Keith

The CUTLER systems can have their fuel delivery curves easily adjusted. Just be careful about leaning things out too much. With the high loads placed on the engines, you won't get too many chances if you go too lean too fast. I'd suggest no more than a 5% change at any one time.

Keith,

My 34 Silverton with 454's runs about 24gph at that cruise around the same weight. Of course several variables influence the outcome but it may be that you are doing quite well

.."a 29 ocean approx 13,000 lbs with twin 350 270 hp crusaders with cuter multiport fuel injection. At 3200- 3400 rpms at 19 knots i am burning 16 gal per hour per engine.. that seems like alot for such a light boat.."

You ain't kidding! My Chrysler 360s burn 8 to 10 GPH each at 2,500 to 2,700 rpms.

Those 454s burning 12 GPH each are about normal (or a bit better).

Jeff

henryf said:

i have a 1987 carver mariner with 2, 350 270 hp crusader engines according to ser no engines are 1986's , my starboard engine burns about 8 gal more fuel than port engine, tanks are a hundred gal each. also all 8 plugs fowl in a short time. choke is manifold mounted and seems to open all the way. spark arrestor is clean. any idea of what to do, plugs have been changed many times , points changed

Click to expand...

yes both propped the same transmissions ok can definitely see it is burning rich