for 302 owners or whoever knows

[tootoot]

My boat is 19' ford 302 W marine cam 15-4000rpm. 225 hp + or-. IO. Weight about 3000 lbs. Oldie but a goodie. Curious what rpm you expect the best economy or if simular boat, what you are getting for fuel burn in the 2-4k range. I know there are variables but was just trying to get an idea. Dont want to invest in a fuel meter. I was thinking about 28-3000 rpm for best economy. Boat is proped out right and bottom clean.

 

[mmainelli]

Re: for 302 owners or whoever knows

That's a lot of engine and outdrive for a 19 footer. You probably have over 1000 lbs sitting astern. Got trim tabs? Had a 302 I/O in my Nova 21 footer, very deep V, about 4000 lbs of boat and engine, with just me aboard. I got 4-5 gph at 2800 - 3200 rpm, with a 4 bbl. You should do better, say 3 - 4 gph, assuming you've got 2 bbl. If you've got a 4 bbl, maintain speed/plane to avoid 2nd bbl set. 2nd barrel set gobbles the gas. If 4 bbl, does 2nd set come in on vacuum or mechanical linkage? If mechanical, re-adjust linkage to get say only 50% butterfly opening at full throttle.

 

[Mischief Managed]

Re: for 302 owners or whoever knows

Best efficiency is going to be right where you guessed, between 2800 and 3200 RPM. The engine will be at it's best volumetric efficiency in that range, and the boat should be up on plane as well. There will be a sweet spot where MPG peaks, but it won't be worth the cost to find it since one side or the other of the peak will be excellent as well. I'd expect 4 to 5 statute MPG at that RPM. The engine will last forever if you keep the RPMs low too.

 

[JasonB]

Re: for 302 owners or whoever knows

Hmmm... My Glastron is a 19' with a 302/Mercruiser. Mercruiser listed the weight of the sterndrive "package" at 950 or 975lbs. I cruise about 3000-3200 and get 4-5MPG with my 2bbl Rochester. Sometime next year I'll be installed my 500cfm 4bbl. I can run a long time n one of my 18gal tanks.

 

[tootoot]

Re: for 302 owners or whoever knows

I'l tell you what, tabs would prob help. Man with the 4 bbl kicked in, the gas gauge moves as fast as the boat. I'm gonna try adjusting the sec butterfly. Surely that'll hurt the hp output though. Dont have much time on the new motor buy think is around 5 MPG. I noticed that at approx. 3000-3200 rpm, my vac guage is starting to get into the yellow range (about 5 inches.) and at about 3000-3200 is when the secondaries are kicking in. Is that normal?

 

[tootoot]

Re: for 302 owners or whoever knows

I'l tell you what, tabs would prob help. Man with the 4 bbl kicked in, the gas gauge moves as fast as the boat. I'm gonna try adjusting the sec butterfly. Surely that'll hurt the hp output though. Dont have much time on the new motor buy think is around 5 MPG. I noticed that at approx. 3000-3200 rpm, my vac guage is starting to get into the yellow range (about 5 inches.) and at about 3000-3200 is when the secondaries are kicking in. Is that normal?

 

[qaztwo]

Re: for 302 owners or whoever knows

I always thought best distance per gallon was right above planning speed.

 

[gatorred]

Re: for 302 owners or whoever knows

mine has 4 cyl it will only turn 3200 at max. it isn't fastest thing on lake,if i want speed jump in my ranger bass boat with 150 xp on it,i had the inboard first when got bass boat, the dealer said it's was worth 1500 doller's that's all we give the estate, what this 6700 check for repair's I got to see this I am not a fool let me see this thing here repair money put it in my name who are you his last living relation opp's it's mine

 

[JasonB]

Re: for 302 owners or whoever knows

Toot, I put a set of Smart Tabs on my boat. Much better plaining and less bow rise. Not sure if it helped fuel use, but they didn't hurt it. My favorite result is that in calm water, this beast of a boat handles like its on rails. It wallowed a bit before.

 

[tootoot]

Re: for 302 owners or whoever knows

Really, My boats like a rocket when you first get on it, I mean its pointing to the sky. I do have a lot of weight backthere. Once its on plane, no prob. It deos woller around at low speeds, might try the tabs. Only prob is I have a transducer on one side and a speedo pickup on the other where the tabs would prob have to go. The last OD I had was a merc and I was able to mount a fin but now have a sterndrive engineering one and the cav plate wont let me mount the fin. Its much thicker and tapperes. Im gonna email them to see if they have one or know of one that will fit their OD.

 

[JasonB]

Re: for 302 owners or whoever knows

When I say wallowing, I mean it would roll more than I liked side/side in turns. I think you are talking more about bow wander. Not a big issue on mine.

 

[vrod2002]

Re: for 302 owners or whoever knows

I'm going to try the 2barrel's first on my 302's.My engine builder swears with the right setup,combo,you can get the same hp results as a 4 barrel.I've seen proof of this on land,the strip.

 

[Mischief Managed]

Re: for 302 owners or whoever knows

HP is a function of how much air you can move through an engine and how much fuel you need to heat it. A smaller number of venturi on a carb is not going to make it require less fuel to create the same HP. If you don't want bad fuel economy, just don't open the throttle as much.