Mercruiser Alpha1 conversion form carb to throttle body

[Galaxie 5.7]

I Just purchased a new boat with a 5.7 Mercruiser Alpha1 drive. My old boat had an 800 OMC Stringer drive with a 350 two barrel carb. It was great on the gas, however this new four barrel just drinks it up. Has anyone every converted their boat from a carb to a throttle body, and if so did it increase performance or fuel efficiency? Just looking at options if there are any.

 

[Bondo]

Re: Mercruiser Alpha1 conversion form carb to throttle body

I Just purchased a new boat with a 5.7 Mercruiser Alpha1 drive. My old boat had an 800 OMC Stringer drive with a 350 two barrel carb. It was great on the gas, however this new four barrel just drinks it up. Has anyone every converted their boat from a carb to a throttle body, and if so did it increase performance or fuel efficiency? Just looking at options if there are any.

Ayuh,.... Welcome Aboard,.... Nope, that's not a popular swap,....

The pay-off is measured in Centuries...

How old a 350/ Alpha,..??

Which carb, the Q-jet, or the Merc/ Weber,..??

What color are the spark plugs runnin',..??

 

[Don S]

Re: Mercruiser Alpha1 conversion form carb to throttle body

How much bigger is the boat than your last one? How much faster do you go than with the last boat. That probably has more to do with it than the type carb you have.

 

[John_S]

Re: Mercruiser Alpha1 conversion form carb to throttle body

As Bondo is elluding to, you probably have some issue with your 4brl that it would have significnt gas milage differences (if you are staying at 3/4 throttle or less) than a two barrel carb. Then again, if you are running 3/4 or more throttle you are running on the secondaries and it will have a more hearty gas appetite.

PS: There could be other very significant differences between your two boats that would account for different millage, hull type, weight, etc.

 

[Galaxie 5.7]

Re: Mercruiser Alpha1 conversion form carb to throttle body

Thank you all for your responses.

The boat is the same size as the last one, weight could be a factor, it is much faster 55 mph last boat about 40 mph, the carb is an Edelbrock, boat was built in 1994, it is a custom boat out of cal, so I think they put on some custom stuff like the carb. I do not know on the spark plugs I will have to check. Is there a color that you have found to be better than others?

It smells rich like raw fuel more that I would expect, does anyone have a good routine for adjusting the idle mixture screws? It is a fun boat I would just love to get the fuel consumption down a little. We do run the boat at 3/4 throttle however we wake board and tube and so full throttle to get out and up. the prop seems to be pitched a little to the top end so I am going to get a backup that is pitched lower for more hole shot and see if that helps a little any thought on that.

 

[John_S]

Re: Mercruiser Alpha1 conversion form carb to throttle body

I'd look down your primary barrels while it is idling. I suspect gas is dribbling down the barrels. A sticking float/needle is probable cause.

 

[500dollar744ti]

Re: Mercruiser Alpha1 conversion form carb to throttle body

put a 2-barrel on it, loose about 40hp, save fuel like the old boat. that was partially sarcastic.

get yourself a fuel flow sender and gauge, watch your fuel flow and you can achieve better economy.

 

[Bondo]

Re: Mercruiser Alpha1 conversion form carb to throttle body

Thank you all for your responses.

The boat is the same size as the last one, weight could be a factor, it is much faster 55 mph last boat about 40 mph, the carb is an Edelbrock, boat was built in 1994, it is a custom boat out of cal, so I think they put on some custom stuff like the carb. I do not know on the spark plugs I will have to check. Is there a color that you have found to be better than others?

It smells rich like raw fuel more that I would expect, does anyone have a good routine for adjusting the idle mixture screws? It is a fun boat I would just love to get the fuel consumption down a little. We do run the boat at 3/4 throttle however we wake board and tube and so full throttle to get out and up. the prop seems to be pitched a little to the top end so I am going to get a backup that is pitched lower for more hole shot and see if that helps a little any thought on that.

Ayuh,.... Cream, 'n coffee colored spark plugs are Good,...

If yer over-fuelin' it, they'll be blacker....

 

[Scott Danforth]

Re: Mercruiser Alpha1 conversion form carb to throttle body

Thank you all for your responses.

The boat is the same size as the last one, weight could be a factor, it is much faster 55 mph last boat about 40 mph, the carb is an Edelbrock, boat was built in 1994, it is a custom boat out of cal, so I think they put on some custom stuff like the carb. I do not know on the spark plugs I will have to check. Is there a color that you have found to be better than others?

It smells rich like raw fuel more that I would expect, does anyone have a good routine for adjusting the idle mixture screws? It is a fun boat I would just love to get the fuel consumption down a little. We do run the boat at 3/4 throttle however we wake board and tube and so full throttle to get out and up. the prop seems to be pitched a little to the top end so I am going to get a backup that is pitched lower for more hole shot and see if that helps a little any thought on that.

If it smells rich, it probably is. what Edelbrock carb do you have, and does it have the right calibration? you may have a fuel system issue.

plus, to go 55mph in a boat the same size as your last one that did 40mph, the solution is simple. only go 40mph to burn about the same amount of fuel. Speed = power. more speed requires more power, which requires more fuel. you are going 38% faster, so you should be burning at least 38% more fuel.