Marinette Boat Forum

We recently sold our beloved 32 Sedan that we’ve traveled 8K + miles aboard over the past 5 years
The good news is that we are moving up and in process purchasing a 1986 39 DC!
One of several reasons we are moving to a larger boat is for the increased fuel tank capacity and hopefully a longer cruising range.
So….does anyone have experience or data on the fuel mileage and/or cruising range of a 39 DC?
We are purchasing the boat at the top of the Tennessee River and our tentative plan is to cruise it down the Tennessee in the spring next year and then UP the Mississippi next summer to the Illinois River and than into the great lakes at Chicago. It appears the new boat will carry 232 gallons (109 gal tank and 123 gallon tank). We believe that their is gasoline available again now at Hoppies again but there seems to be some uncertainty there. Obviously, we will have to do some investigation in determining for certain where gasoline will be available. We know that there will be at least one long stretch of 200+ miles with no gas available and we would be going upstream against the current. Obviously timing if this leg will be of importance.
Mainly looking now for any actual data anyone can share on their experience with range on their 39 DC. Thanks

Our '32 FBS got a fairly steady +/-1mpg when we cruised on the Chesapeake Bay with and against wind and tide. You'll be battling a steady downstream river current which can be significant. I am guessing you would do well to plan for.75 mpg unless you plan totry to hold the boat just over planing speed, its most efficient point. I am amazed there are places with 200 mile gaps. Wonder if there is a fuel delivry srvie near your half way point. Otherwise, you'll need some big extra tanks to make that stretch. have fun/good luck

There is a way to mitigate the amount of fuel usage cruising on a river and when your cruise is a relatively long one, the savings do add up. This would be what I call (it may go by another name ) " current manipulation".
Principle: a river's current, on a straight section, is fastest in the middle/nearest the channel. This is because the water has no real obstacle to its flow. By the very nature of the flow the opposing bank's flow is slower** and cruising upriver there takes less effort (ie. Less fuel usage than cruising in midstream to travel the same distance).
** traveling this way does take some precautions...
1. You don't want to cruise too close to the shore which could result in potentially running aground on a low sloping sand/silt bar.
2. You need to transition from one side of the river to the other when entering curves in the river (see 'curves' below)
When traveling DOWNRIVER staying in the current provides an extra boost to your mileage/GPH burn rate (you go farther per gallon used)

CURVES -
Curves in a river also can help -
Traveling DOWNRIVER - enter the outside curve to maintain the downriver flow benefit.
Traveling UPRIVER - stay closer to the inside bend - the flow here will be less, and closer to the bank will actually have a flow that flows slightly upriver...
The flow upriver may not be that much but you won't be fighting a downriver current.
** Again, caution and awareness are paramount to avoid snags which will settle in these slack areas or sand/silt areas where sediments have an easier time to settle out of the water.

Bank to bank transitioning - this can be a judgement call...
- is there boat traffic needing to be avoided? If so, how fast is it moving (aka - how much time is there to complete the cross river maneuver before becoming an obstacle to the aforementioned traffic?)
- How fast is the current to be crossed?
If crossing traveling upriver and a direct 90° crossing is done, the current will push the boat back downriver, causing a loss in forward travel (not ideal). Better to take a gradual upriver tack so forward (upriver) movement is maintained.
If transitioning heading downriver and you're attempting to stay in the current in an outside bend, it's less of an issue, just be aware of traffic in both directions. Barge operators stay closer to the main channel but will utilize current flow in something of a similar fashion, when it's feasible to do so. It's handy to have the river help when you've got a large tow whose draft is 7' below the surface and the current flow can help you move along.

Bill

Good information Bill and well worth traveling with some of the techniques on any long river voyage. Thanks

With gas prices on their way to stratospheric numbers, I'm glad I no longer run a twin engine boat! (But I sure miss her.)

Jeff

The "current manipulation" thing is real. We met a couple canoeing across continent. They had already canoed upriver halfway to the Great Divide. I asked how hard it was going upriver. They said aside from all the zig-zagging, easy. They rode the back eddies the whole way, paddling only cross-current to catch the next back eddy

Strange that you mentioned that, for I am now a kayaker; and it's white and blue, as were the last 40 years of my boats (by pure coincidence).

Made a run against the river current just this morning--exhausting--but I got a nice free ride back (when I needed it the most). Named the little boat 'Tippi Hendren' and, after a few embarrassing moments, I am able to get in (not too gracefully) and out without killing myself!

I'll look into that zig-zagging.

Slow Jeff

A quick update:
We made the sale final and took possession of our 'new to us' 39DC this past week.
LOTS of elbow grease and tinkering on misc systems but got her ready for cruising. We did a couple of cruises around the Lake Telico area. We ran 40 miles at 2500 RPM (17 MPH) and got .8 MPG