I had a 1966 wood 36' Pacemaker with twin 275hp Chrysler 360s. It would do about 16-17kt top. At about 10kt it burned 15gph. This was with low hour engines in excellent condition.
, it had 2-100s and 2 25s. I figured on a usable range of 100 miles.
To guess at the size of your tanks
, think in terms of 55 gal tanks
. I bet yours are about 100 each. Maybe a little bigger, but I'd be very surprised if they are bigger than 150 each.
With the engines you have, and my guessitmate of fuel
capacity, if you stay under 8 kts, you might eek out a 100 mile usable range.
FYI: My interpretation of the rule
of thirds for estimating range is 2/3 for the route
and 1/3 for safety
reserve (not 1/3 to play with). But then, I always plan on the conservative side.
There are a lot of variables. What you gotta do is get all the figures you can nail down (especially fuel capacity), and then estimate and do your first trip based on the most pessimistic figures you come up with. Based on my guesses above, I'd limit my first trip to about 75 miles and see how much fuel I used.
When you do your first test run, carefully note your speed. There will be a drastic decline in efficiency when you start getting above about 8kts. If you do your first test at 8 kts and decide you have a 125 mile range, so you plan on 125 miles for your second trip, but do it at 12kts, you'll be in for an unpleasant surprise.
Also remember, if you only have a 100 mile usable range, planning guides are a must for long trips. Pre-select fuel stops along the way. I made sure I had one scoped out about every 50 miles. Then, I called each one the day before to make sure they were open and had fuel. Good thing, too. One that was located in a critical part of my route
said they had sever shoaling and I could only get to the fuel dock
at high tide. I stopped at one 40 miles earlier even though I had plenty of fuel, so I could bypass it.
Once I planned on a 110 mile leg down the Chesapeake, had seas quartering off the bow with a strong head wind
. En-route I changed plans and chose a marina about 5-10 miles closer. Even then I had less than 25gals of fuel left when I got to the fuel dock
. Enough fuel for only 15 miles is way
Basically, I'm just saying that in a short range boat, planning is even more critical.
Remember, what I've said above is based on a lot of assumptions and guesses. No warranty expressed or implied.