CrazyCat57

I have a holley 4150# 750 cfm vac secondary on my stock 1992 330 hp 454. The boat turns 4260 rpm wot fully trimmed with 4 adults and a full load of gas and the book says 4200 to 4600 rpm. I am running a new rev 4 wedged and ballenced 4 blade prop. I think I am proped just abought right. I have plenty of power out of the hole, even some extra. Most all of my running is cruising around 2700 to 3000 rpm,hardly ever using wide open throttle.The boat is a 23 ft bow rider and weighs about 3800lbs empty. Like a lot of people I am looking for better gas milage, right now it gets about 1 1/2 mpg and I think it should be a little better then that. As far as I know the carb is set to factory specs. I havent opened it yet to see whats in it for calibration. Can I go to a heavier secondary spring and smaller primary and secondary jets without damaging the motor [how much smaller]. I am willing to give up some preformance for better gas milage. Thanks for any replies.

David Stotz

You probably could but if you lean it out to much the money you saved on gas you'll be spending for a new motor. I would say most people here run a little on the rich side to avoid detonation problems, I know I do. Why don't you remove the flame arrestor while under way and note the throttle position just before the secondaries open. Do most of your cruising at this point. That should save some gas.
Dave

the duke

The amount of gas that you would save by going leaner on your jets is a minimum quanity. The down side is detonation/leaning out the motor and burning pistons. gas is still cheaper than rebuilds.

CrazyCat57

Do any of you think there would be enough improvement to justify a edelbrock preformer manifold and a 600 cfm edelbrock carb? Edelbrock recomends the 600 cfm 1409# carb for a 454 turning in my rpm range. This boat is run only in fresh water. Edelbrock also suggested if I wanted to change cams, to go to Crane or Comp for one of their marine cams.

David Stotz

What are your objectives in doing a cam change. Most people change cams to increase performance, not gas mileage. If gas mileage is still your priority as stated in your first post, leave the motor alone!
Dave

Strip Poker 388

iTrader: (6)

Your spending money to save on gas money, youll never recoop

the duke

There is little if anything that you are going to do to a BB to save gas in a boat. The best way is to prop it right, and then just not run it at WOT. If you read any of the boating Mags, you can see how much fuel that the boats use at X rpm. as you back up the economy improves greatly. Like Strip Poker said, if you spend several hundred dollars on a smaller carb, you will never make up that cost in gas savings, let alone losing performance.

CrazyCat57

I did change a 302 cu 2bbl ford 188 hp I. O. to a edelbrock 4 bbl carb, edelbrock preformer manifold and their lowest rpm cam that they had at that time. I gained preformance along with a sizable increase in gas milage. I ran that boat for 6 yrs trouble free. I have good enough preformance with my 454 but a little more is always nice. Edelbrock says that by using a 600 cfm on my set up and the rpm I am turning it should increase my low and mid range but I may loose a couple mph on the high end, I dont care about the top speed. I plan on keeping this boat for a very long time, and at the cost of what gas has been doing it wouldnt take all that much of a gas milage increase for me to get to the break even amount of $$ spent on the engine. I dont care that much about the preformance, either more or a little less would be acceptable to me. I was extremly happy with the changes I made on the 302 ford and looking for opinions befor I do anything to the 454 chev. Thanks for any replies

the duke

changing from the 2bbl to the 4bbl is a tottly different thing. On the 2 bbl, you were always using all of it. When you went to the 4bbl, at cruise you most likely were only using the primary 2, and they were drawing less cfm than the original 2 bbl.

On a 454, I think a 600 cfm carb is too small for the engine,(Using the Holley chart which is pretty conservative, they say 700-750) and I love most edelbrock products, EXCEPT for their carbs, which are pretty much a Carter carb with their name on it.

By the time you buy the new carb/intake etc you will have spent how much? $500? at $3.00 a gallon, thats 167 gallons of gas. If you could double your fuel economy (not likely) how far can you go on that much gas? and that would be to just break even.

CrazyCat57

I agree with you on the 2 bbl to 4 bbl making the difference on the 302. I just got off the holley web site and punched in my stock 454 cu turning 4600 rpm, that is the max it would ever turn, They also show to use a 600 cfm unless I need a spread bore then it would be 650 cfm. Edelbrock and Holley both say 600 cfm. I am thinking way ahead, in terms of many years of running this same boat. I am not looking to break even in 1 or 2 years but many more years of running. If I could gain 1/2 mpg over my 1 1/2 mpg that I get now it would mean a pretty good savings in the long run. Who knows what gas will do in the future. The more gas costs the bigger the savings will be to me once I reach the break even point. Holley has always been a big name for speed but not for economy and staying in tune. I used to run a Holley and only Holley when I raced a Chevy powered jeep but the Edelbrock on the 302 boat was trouble free for more then 6 yrs. Thanks for your replies. I hope to keep getting some input on this.