'88 Quadrajet Carb specs

[Stan's Customs]

Afternoon Mariners....<br /><br />I have just rebuilt a Quadrajet that came on a 1988 Four Winns with the 350 Chevrolet engine. According to the rebuild kit the carburetor is for the 262 (6) engine. The number is 17085010 on the carb. <br /><br />OMC tech doesn't have the information...Kent the guy that might know is out for a couple of days and so on.Thought some of the pros on this forum could help out.<br /><br />I was wondering if OMC sometimes mismatched carbs at the end of a model year or something ? If so did they rejet or just use them the way they were. This boat has only had 2 owners and they believe it is the original carb...old boat though and they may have forgotten if something out of the ordinary was done in the past.<br /><br />If that was not a possibility...does any one have any jetting and or metering rod specs. Perhaps another mechanic has already rejetted it if that what is needed. I didn't notice that carb numbers showed to be for the V6 till I had it reassembled. However, it is still sitting on my work bench till I find out what the differences are in the two carbs (V6 vs V8). If my memory serves me it has a pair of 71 jets . I didn't look at the metering rods real close so I don't know if they are even marked.<br /><br />Thanks to any one who has any idea what these things came with...<br /><br />Stan M.

 

[Laddies]

Re: '88 Quadrajet Carb specs

looking at a NAPA reman. carb book both 17085010 the carb you have and 17086117 the carb. for the 5.7 cross to a NAPA 18-7615 carb.

 

[Stan's Customs]

Re: '88 Quadrajet Carb specs

Thanks laddiesservice...<br /><br />The numbers from the build sheet that I have indicate that the 17086117 carb is one of three for the 454 powered OMC...and that the only 350 engine carb is 17059286.<br /><br />There are two listings for the 305 engine , neither of which correspond to any of the others, and likewise one carb for the 427 OMC.<br /><br />The 17085010 is the only listing for the 262 V6 (which is the one this 350 boat has on it)<br /><br />Mind you that these numbers come from the carb kit manufacturer's listings for O.M.C. Outboard Marine Corp. These numbers come directly off their rebuild sheet included with the carb rebuild kit. I generally take these listings with a grain of salt...but they seem rather well defined in this case, so I am taking a closer look. <br /><br />I'm not saying that are accurate at all.....just that that is how they list the carbs.<br /><br />On the other hand if they are correct and the two numbers are for a 454 and a 350 respectively...it would seem that NAPA has a middle of the road carb listing that can supposedly be used on the 454 or the 350 engine. Of course it will work...but it would not be the optimum jetting for one or other of the engines...maybe both. <br /><br />So what I really need to know is how the 4bbl carbs were jetted for the 350 engine specifically , if that can be had ??? I may not be able to get this information anywhere...but I can build it to specs if I know what specs are....<br /><br /><br />Thanks again for your interest....Stan

 

[Stan's Customs]

Re: '88 Quadrajet Carb specs

oops<br />I meant to say.....<br /><br />On the other hand if they (the carb kit manufacturer) are correct and the two numbers are for a 454 and a V6 respectively...it would seem that NAPA has a middle of the road carb listing that can be used on either the 454 or V6 engine. Of course it will work...but it would not optimum jetting for one or other of the engines...maybe both.<br /><br />SO SOLLY...STAN

 

[Buttanic]

Re: '88 Quadrajet Carb specs

Jets are sized more in relation to the size of the carburator's venturi diameter and CFM flow than to the size of the engine or number of cylinders. If the size of the venturi and the cfm rating is correct for the engine more than likely the jetting is correct.

 

[Stan's Customs]

Re: '88 Quadrajet Carb specs

Hi and thanks for your input Buttanic..<br /><br />I can't disagree with your post, however quadrajets have several primary needle and jet combinations for different engines. While the jetting could be dead on for this CFM carburetor on a small engine, it could be totally wrong for the another engine application. <br /><br />Since we arn't dealing with a wide open throttle situation with the primary jets, maximum CFM performance isn't all I want to be sure of. I am also concerned about lean or rich mixtures while operating on the front venturis...specifically idle circuit and a tromp from dead stop.. A 454 for instance would require a much richer idle circuit than a V6, due to more air flow...remember we are not talking about WOT. A big engine requires more air and fuel than a small engine to idle at the same rpm, correct? There are no venturi limitations at the RPM's in this operating range, only at WOT.<br /><br />I imagine this carb will be allright and I know the air jet adjustment will compensate for much...but performance would be below par if indeed it were a 6 cylinder carb mounted on a 350 engine....at least it seems that way to me.?<br /><br />What do you think?<br /><br />Stan

 

[Buttanic]

Re: '88 Quadrajet Carb specs

Quadrajets are notoriously hard to tune. When they are dead on they are a good carb but when off good luck trying to tune the mid range with all the different combinations of jets and metering rods if you can even find different ones to try. Plus they have problems with leaking fuel around the jet well plugs after a while. Why they are still putting them marine engines is beyond me. I prefer the Holly, simple and easy to tune and parts are readly available.<br />Your best bet is to run it and read the plugs to see if it needs a change.

 

[Stan's Customs]

Re: '88 Quadrajet Carb specs

Roger that Buttanic...<br /><br />they have to be dead on. Thats the reason I'm trying too get specific jet and metering rod specificationsfor this boat application.<br /><br />I have real good luck with the Q-jets on our restoration projects...guess familarity and 30 years building them has a lot to do with it. We do a lot of holleys too..but generally speaking on street applications, holleys don't hold the street tune as well as the Rochesters (providing they were tuned right to begin with).<br /><br />Another big plus for the Q-jets on street driven classics is fuel economy...they usually do real well compared to most Holleys. (once again providing they were right to begin with)<br /><br />One of our problems is ..since we don't do boats but once in a blue moon, testing is a pain. We have to get 'em close on the muffs and trailer them to a lake and so on, which is time consuming if you are just guessing. That's the nature of the beast though, so we just deal with it.<br /><br />In fact we have just come in from our first lake run on this boat...Shifts much better than I thought it would, based on the clunking it was doing on muffs. Comes out of the hole good, idles well though it needed idling up about 150 rpm in the lake. BUT...in the upper RPM ...say 3500 on, there is a problem. I thought because it popped a couple of times maybe the valve springs were weak. I changed my mind about when I realized that trimming the drive up or down had an effect on the performance...like it started to miss a little, loss of rpm thgough not extreme. Ignition interrupter malfunction maybe?? I don't know...<br /><br />I will start a new post on this ...we really are expecting a cold front tomorrow and I'm trying to get this thing running right, before I have to put it up for the winter. We need it next spring for our kids and grandkids at our family reunion. I'll worry about it all winter if I don't at least have it diagnosed.<br /><br />Thanks for your help..boats have their own quirks just like everything else, it's good to have some help from those that know them well.<br /><br />Stan