Running cold and getting poor fuel economy

[Redrig]

Hello,

1977 OMC electric shift behind a Ford 302 I recently changed my impeller.

I took my boat out this past week and have a couple of questions.

1.My temp never got above 115 or so, and I had a couple of nice long drives and it neven warmed up. That seems very cold, almost like a stuck open thermostat. I recently changed my impeller. what temp should I be running at approximately ?

2. My fuel economy seemed to be very low, my boat has a 45 gallon gas tank and I used about 3/4 of the tank and didn't go all that far.I figured that I could drive all week with 45 gallons.

I realize that this is an extremely loaded question but what should I be getting as far as mileage goes? (and how do you even refer to that with a boat?) MPG or GPH ?
does anyone know roughly what the fuel consuption should be on a 302 per hour say taching at 3k? that is where I have been running to keep on plane and that puts me at about 23MPH.

3. last question, could my running cold situation contribute to poor fuel economy ? I have no way of proving this but it seems my last trip I did way more boating with less fuel.

Thanks in advance.

 

[Howard Sterndrive]

Re: Running cold and getting poor fuel economy

160F would be more like it

I like this page for mpg/ gph references - pretty accurate
the Ford 302 would compare to AQ200 or AQ211
http://freespace.virgin.net/simon.sherlock/Volvo_fc.htm

 

[bruceb58]

Re: Running cold and getting poor fuel economy

Depends on the size of the boat what mileage you could get which you don't specify. Let's assume you have a 22' boat that gets 4MPG. At 23 MPH you consume 5.75 GPH so your 45 gallon tank would last 7.8 hours.

As far as your temp is concerned, you should check your thermostat and then also check with an IR gauge what temp you are actually running at. The gauge may be not indicating the actual tmep.

 

[Redrig]

Re: Running cold and getting poor fuel economy

I apologize, its an 18 footer.

 

[QC]

Re: Running cold and getting poor fuel economy

The data on Howard's link is Imp gallons. 4.256 liters vs. 3.785 for US gallons . . . reasonably big difference

 

[bruceb58]

Re: Running cold and getting poor fuel economy

I apologize, its an 18 footer.

Do the calcs with 5 MPG. Obviously in a week, you could run your boat anywhere from a hundred of hours to tens of hours so the exact time you are running at a certain speed is necessary or get yourself a flow meter. I have a flow meter on my boat in my signature and I get less than 3MPG at my most efficient speed.

 

[QC]

Re: Running cold and getting poor fuel economy

I'd be surprised if he got 4 with that older, carbed system. I think 5 is a reach Bruce . . .

 

[bruceb58]

Re: Running cold and getting poor fuel economy

I'd be surprised if he got 4 with that older, carbed system. I think 5 is a reach Bruce . . .

Trying to make him feel better!

 

[Redrig]

Re: Running cold and getting poor fuel economy

Does anyone by chance know the part number for the thermostat or the thermostat kit that I would use for my boat ? Or a link or something that would point me in the right direction.
My manual doesnt have any numbers or anything.

again its a 1977 OMC with a ford 302 - 175hp

 

[bruceb58]

Re: Running cold and getting poor fuel economy

Call these guys:
http://www.fasteddiesmarineparts.com/

 

[Redrig]

Re: Running cold and getting poor fuel economy

thanks for that. they found the kit for me. Sierra 18-3653.

So can running at 115 degrees cut your fuel effeciency in half ?

I probably didnt go more than 60 miles and used a little over 30 gallons.

 

[bruceb58]

Re: Running cold and getting poor fuel economy

No it won't.

Unless you know exactly how far you went, all bets are off on calculating a fuel economy number. How did you know you went 60 miles. Did you completely fill your tank when you started and completely filled it up when you were done to calculate the fuel used?

 

[Redrig]

Re: Running cold and getting poor fuel economy

No it won't.
Did you completely fill your tank when you started and completely filled it up when you were done to calculate the fuel used?

yes, I filled it up before and after. used 32 gallons.

the 60 miles is just a guess. I went to lake powell and used the mileage bouys to get me close to that number, but ya there is no way to know for sure.

Maybe my choke plate on the carb isnt opening properly or something.

 

[NW Redneck]

Re: Running cold and getting poor fuel economy

Hey RR, I have the same setup as you but a '76 in an 18' Cal-Glass. I've roughly figured out my 'mileage' at about 3.5 - 4 mpg cruising at about 35mph @ 36-3700rpm. 60/4=15gal, so either you traveled farther than you thought, or you could be burning up more gas than 'normal'. I have a raw-water cooling system and I run between 160-170* in both lake and ocean.

 

[Canman38]

Re: Running cold and getting poor fuel economy

So have you figured out your problems yet? I would love to know if the thermostat fixed your running cold issue.

 

[Redrig]

Re: Running cold and getting poor fuel economy

Yes I think I did get my issues resolved, my last trip my boat ran like a champ and was very economical gas wise.

after this initial post I changed my thermostat and also threw in a tune up kit. I had never messed with points before.

The points were definately the difference maker, my last trip I probably went close to 80-90 miles and use only 1\3 of my tank, I initially was thinking my gas gauge was broken, didnt think I could be getting that good of mileage. I haven't topped off the tank yet to get the exact number.

my points must have been absolutely shot on my first trip of the season, they had to have made my timing drift dramatically.

I have so much more power as well right now, getting up on plane faster. goosed the throttle and got it up to 40mph, no way I could have done that before.

I never realized the maintence that was involved with points but I learned my lesson now, that first trip of the season I probably wasted 150 bucks in gas easily.

my temp is now runnign at 160 where it should but I dont think that played a major part.

so moral of the story from me is to maintain them points!

 

[sethjon]

Re: Running cold and getting poor fuel economy

If your pointx wer that bad your boat must have been running really bad and I'm surprised you didn't notice it. Personally, I really like points and if you keep them adjusted properly and change them when needed you won't have any real problem related to tune up. Glad you got it fixed.

 

[Redrig]

Re: Running cold and getting poor fuel economy

If your pointx wer that bad your boat must have been running really bad and I'm surprised you didn't notice it. Personally, I really like points and if you keep them adjusted properly and change them when needed you won't have any real problem related to tune up. Glad you got it fixed.

I am sure a veteran with points would have noticed an issue with it, problem for me was I honestly didnt even know what points were and were they were located. I made a very noobie post on here asking for help changing them out and some peeps walked me through the process.

I like points as well the more I learn about them and have changed a set now. For my boat I am all for simplicity and points seem very simple and easy to fix if you run into a problem on the water.