1990 Mercruiser 5.7 carb spacer

[realski1]

I have a 90 ski supreme I purchased used several years ago. It stumbles on acceleration(too much fuel). Choke is not sticking and top and bottom butterflies are opening properly. I ran numbers on carb and it looks like a 1975 gmc quadrajet has been installed. Im going to replace it with a marine carb but am needing to know if an angled spacer is needed? My boat doesn't have any spacer and it has the factory spreadbore intake manifold on it. Any help or suggestions are greatly appreciated! Thanks

 

[NHGuy]

Re: 1990 Mercruiser 5.7 carb spacer

I would go no spacer, my boat is really nose up on lift off and I can plow forever without any loss of fuel. It has a Rochester Quadrajet, By the way, which has a carb # that's been the same for years. My motor is an 88, my boat is an 89 and my carb # is from the 70's with an 88 production date.

 

[Don S]

Re: 1990 Mercruiser 5.7 carb spacer

You need the angle spacer,
The direct drive inboards have a lot more angle on them than any IO ever sees.

 

[realski1]

Re: 1990 Mercruiser 5.7 carb spacer

Thanks! That is what I was thinking. Does anyone know if the angle spacers are available for the spread bore intake manifold? My Quadrajet number is 7045213 F6 C YA made by Carter for GMC. The boat runs great up to about 3000rpm even under load pulling skiers but if you shower down on the throttle it stumbles until you let off and ease into the throttle. I bought the boat this way and have just dealt with it but this summer I want to fix the stumble. Thanks

 

[realski1]

Re: 1990 Mercruiser 5.7 carb spacer

I forgot to mention my carburetor has no vent tube from the fuel pump nor does it have the turn down vent on the air horn which leads me to believe the carb is from a car?

 

[frantically relaxing]

Re: 1990 Mercruiser 5.7 carb spacer

Here's a pic of a marine Q-jet. Has no turn down vents, the circle/arrow is where the fuel pump overflow line connects--

found another pic, this engine out of an '84 Bayliner now resides in our old Sea Ray, you can clearly see the overflow tube on the front of the carb--