New intake and carb on Mercruiser 5.7

[HasseEd]

Have bought a new intake (GM high rise mercruiser mag #14098242#) and Edelbrock 1409 and wonder if I will gain some HP or torque. The old carb(Rochester) was bad and looking for better fuel economy and cruising speed(not top speed). The boat is an Sea Ray 250 Sundancer 1990.

Regards,
H.e

 

[Grub54891]

Re: New intake and carb on Mercruiser 5.7

Can't tell ya if it'll gain you anything. But I'd be darn shure the carb is a marine carb. Personally I don't believe in changing what the mfg set it up with. Quads are easy to rebuild,and when set up correctly work well. You want horsepower and torque,and economy? Can't have both in my opinion.
Grub

 

[adimice]

Re: New intake and carb on Mercruiser 5.7

I didn't change my manifold, but got rid of my old Q Jet. The engine would fade under a load had the Qjet rebuilt, but still no good. Put the 1409 on and bada boom bada bing, she ran great. Hope you have the same result.

 

[Walt T]

Re: New intake and carb on Mercruiser 5.7

No, there will be no noticeable difference in power. Doesn't mean there isn't a gain, just means not enough or in the right rpm range to make a difference. You can't think like an auto enthusiast when going for more power in a boat motor. A higher CFM carb is completely useless in a boat and most cars because that only comes into play at higher rpm and boats are generally limited to 5000 which is easily fed by 500 cfm 2 bbl. Those who claim more power with a manifold and carb switch I would submit the original setup wasn't working correctly. HOWEVER it's fun to do this stuff and it'll look nice so why not? Who knows, might even notice a power gain. You bought em so install em. You'll like how it all looks. as far as fuel economy, sorry it's 2-3 mpg no matter what you do. I build engines from the ground up for marine performance and it takes a strong base engine to make real gains. Changing cams tends to make things worse in a stock motor. Go to it and have fun, let us know the results next season. Just don't expect too much.

 

[NHGuy]

Re: New intake and carb on Mercruiser 5.7

New tends to trump old. The 1409 is a great replacement for a 5.7. I bet it runs better. And if your old carb was not right there's every chance your new one will give you back lost performance. Performance like power, smoothness, and the tiniest little bit better fuel economy. It won't be enough to really call a dollar savings cause that Sundancer is a lot of boat to push with a 5.7, but don't we all want our boats to run correctly?
Of course you will need to set it up. To me that's a big part of the fun. Look in the supplied paper work for the jets and settings that it was built with. And obviously give them a try unless something stands out as wrong. Look up the installation process in the paper work or here. http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf
If you bought the carb for your exact application it might already be correctly jetted.
Also save the old Quadrajet, you can fix that up at your leisure. Just in case the 1409 does not make you happy. I did my Rochester as a winter project last year. Partly cause I'm cheap, partly cause it was OE, and partly cause I needed a boat project. It was a good education.
I'd compare the 2 intake manifolds. You probably bought the same as the motor already has. If so just return it, no sense replacing a functional cast piece. That's some gas money, or for some other use!