Marinette Boat Forum

In 5 years of owning a boat of my own, I am finally making a trip out of my little 20 mile area. I am heading to a sternwheel festival about 80 miles down river. I have twin chrysler 340s each connected to their own 70 gallon gas tank. Does that mean that I will only get about 70 miles out of the boat if I average 1mpg? I know I will probably get better than 1mpg, but I am using that as a good baseline.

Yup! Unless you can refuel on the way, you'd better buy a few 5 gallon plastic tanks and bring them along.

Jeff

I Ave done several houseboat deliveries in that size range of 45 50 ft. with twins.

Running 9 mph most averaged close to 1mpg total .
The Seacrest is lighter so should do better.

You should be able to run 100+ miles with reserve.

Now running upstream that is a different animal.

Dave

Forgot about that river current factor!

Jeff (Typical bay runner.)

What are you guys getting for mileage?1986 32 Sedan with 360's I'm thinking I'm getting about .8 mpg at 3200rpm.

My one year earlier, similar boat got 1.2 MPG at 2,500 rpms/ 18 to 20 MPH. I worked on it a LOT to get it that good, however, with 17 x 15 four blade props, Edelbrock 1409s, and other tricks.

Jeff

Fastjeff
Do you think that you would have the same numbers with 17 x 15 3 blade props?

Jeff,

What are some good areas to work on for fuel economy?

I'm adding another fuel tank to my single 318 to increase my range. I'll start doing tests after Erika passes.

The new ignition system should help a little.

While Jeff is ruminating, I'll weigh in. Top items for me: clean bottom makes a huge difference. Load you're carrying and how you distribute it. Less here is more. Trim (angle of boat through the water) so you're not plowing (bow up high). And speeds (crawling gets good range but you wonder whether you'll ever get there and top speed will get you there in time for lunch but at a fuel penalty).

My personal note on clean bottom: Was getting 15-16 mph at cruise around 2800-3000 rpm. Cleaned the bottom and speed shot up to 20 mph at same rpms. That cleaning paid for itself.

I 2nd Joel! Just put mine back in after a complete bottom restoration. Back to bare and done correctly. Great marina and price was reasonable and work was very high quality..

At 2,200 rpms my 29 with full tanks fuel and water... 15.6 MPH. Was able to hold on plane at 2,000 rpms at about 12 mph.

MPG estimate went back up to 1.6 mpg. I was at 1.1 before bottom job. Now how long will it stay clean? No very LOL