MPG question - deciding if a trip is possible

ArcticCat · Jul 24, 2010

Ok, the boat - 21' 1992 Thompson Calae - 4.3 vortech. 20 gallon tank.

I want to make a trek from Cedarville, MI to Mackinac Island, MI (Lake Huron). Google says its about 18 miles one way. 36 round trip. I figured it would get at least 2 mpg... lol, but hey, I dont know, so Im asking... hate to be calling the coast guard for a tow.

Can I make it there and back without needing to fuel up?

I know conditions (winds and waves) will play a role. Lets call it 1' or less. The boat belongs to my wife's family, this is why I do not know what it's capable of for distance.

Any and all "help" is much appreciated.

JoLin · Jul 24, 2010

Re: MPG question - deciding if a trip is possible

Can you buy fuel at Mackinac if necessary? I can't vouch for the mileage of your boat. I think others will chime in.

If you can't buy fuel enroute, the 1/3 rule needs to apply- 1/3 out, 1/3 back, 1/3 in reserve. Fuel consumption increases dramatically if wind and current are against you.

PS- The Coast Guard won't tow you. They don't do that.

ondarvr · Jul 24, 2010

Re: MPG question - deciding if a trip is possible

Take an extra can with you.

ArcticCat · Jul 24, 2010

Re: MPG question - deciding if a trip is possible

I can take a 6 gallon can with me, thats no problem. I will be into the wind on the way there, to my back on the way back... most likely. No gas docks at the island. next closest port is St. Ignace and thats another 20-30 minutes in the wrong direction.

Thanks again for the replies.

Ken

GatorMike · Jul 24, 2010

Re: MPG question - deciding if a trip is possible

The coast guard hasn't been in the towing business for years. If you call them for a tow they will just call Seatow for ya. If that is all the further you are going just carry a couple of 5 gallon spare cans with you.

RWilson2526 · Jul 25, 2010

Re: MPG question - deciding if a trip is possible

I think you'll do better than 2 mpg. I know its a 4.3 but when I had my 3.0 I could make a trip like that on less than 10 gallons. Somebody with a similar engine and setup must have some good numbers.

Mischief Managed · Jul 25, 2010

Re: MPG question - deciding if a trip is possible

My 7.4 equipped, 6000 lb, 25 footer gets 2.2 to 2.6 MPG (load and waves make a big difference) at cruise . You can count on at least 3.5 MPG at 25-30 MPH.

kenmyfam · Jul 25, 2010

Re: MPG question - deciding if a trip is possible

You need a test run for a few miles out and back with a full tank then top it off again when you get back. Calculate from there. Then use the 1/3 rule as stated already. Carry as much extra fuel as you need to make certain you get back with fuel in reserve.

Fireman431 · Jul 25, 2010

Re: MPG question - deciding if a trip is possible

ArcticCat said:
Ok, the boat - 21' 1992 Thompson Calae - 4.3 vortech. 20 gallon tank.

I'm sure you know your boat better than anyone, but are you positive that it's only a 20 gallon tank? I've had (3) 20' boats from different manufacturers and the smallest tank was 45 gallons. Why would there only be a 20 gallon tank in that boat?

ArcticCat · Jul 25, 2010

Re: MPG question - deciding if a trip is possible

I believe I mentioned it is not my boat, its my wifes family. If I didn't, I meant to. I was told it has a 20 gallon tank by them.

Ken

Fireman431 · Jul 26, 2010

Re: MPG question - deciding if a trip is possible

ArcticCat said:
I believe I mentioned it is not my boat, its my wifes family. If I didn't, I meant to. I was told it has a 20 gallon tank by them.

Ken

Sorry...read right over that. Might want to double check the capacity. Just seems low to me.

**EDIT** Just looked online and there is a 1994 20' for sale that says it has a 90 gallon capacity. What gives?

Isaacm1986 · Jul 26, 2010

Re: MPG question - deciding if a trip is possible

20 gallons seem low to me also. It should be a bigger tank than that. I had a 21ft reinell and it had a 45 gallon tank in it.

If you are averaging 2mpg in the boat, 18 miles 1 way would be 9 gallons of gas. round trip would be 18 gallons (i know this is basic math). Just take a extra 10 gallons in a couple cans and you should be just fine.

dingbat · Jul 26, 2010

Re: MPG question - deciding if a trip is possible

When calculating consumption you calculate for the worst case scenario. A good chop or head wind can easily double your fuel consumption. There are reasons for the 1/3 rule

tcgobucks · Jul 26, 2010

Re: MPG question - deciding if a trip is possible

Never been there, but just looking at a map it looks like either Mackinaw City or St. Ignace both have marinas and they're both about 3 miles from the Island by water. Why not just run over there and fill up before heading home. That's a lot less hassle than carrying extra fuel. At 18 miles each way you've got plenty of fuel, even if you have a headwind.

MPG question - deciding if a trip is possible

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