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The same Carburater for two different motors?


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cnewton
Novice

Jun 4, 2022, 12:28 AM

Post #1 of 7 (343 views)
The same Carburater for two different motors? Sign In

I have a 1984 Mercruiser 5.7L 260hp V8. The Rochester quadrajet (17090210) that had run for years on it finally needed replacing. I purchased a re-build that was advertised as being a replacement that was built and calibrated for the Rochester Quad 17090210. Felt great, then I noticed it was also built and calibrated for the Mercruiser 350 Magnum engine. I don't have a Magnum. The carb arrived and looked almost identical, intalled easily iand it started right up but it ran terrible, rough, jerky and I had to use the throttle to keep it going between 1600 and 2000rpm. It wouldn't run on it's own or smooth out so I shut it down. Is there something I should be doing, adjustments....


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 4, 2022, 3:29 AM

Post #2 of 7 (331 views)
Re: The same Carburater for two different motors? Sign In

OMG -SAVE ALL OLD PARTS!
I got old this is the last of the best Carb known to mankind + misunderstood by all!!

The CFM = cubic feet per minute is about right those 17,0000 #s matter don't freak out over then totally.

These take some tools to tweak to perfection still not reality will in a boat (owned many) this engine & carb can and will run dry (fuel in bowl in carb) be a pest like it was out of gas b-cause it is! Flooded easily can and will happen not knowing that.

HIT ME UP. SPOT ON WHERE ARE YOU STUCK? I'll re- read your post and maybe it's in there please know I KNOW these carbs was the best and did re-do them on a kitchen counter for techs IDK how many but took a sense of humor to tolerate me - RIP best person anyone could know of,

Tom



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 4, 2022, 3:48 AM

Post #3 of 7 (326 views)
Re: The same Carburater for two different motors? Sign In

The only thing you have to be real careful about with these carbs is that they are made for marine use and are non-vented.

I think the only way you could see that bad of a running situation is either you have the wrong base gasket that is sucking air somewhere or your vacuum lines are messed up somewhere, assuming the carb is not simply defective and flooding.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



cnewton
Novice

Jun 4, 2022, 7:55 AM

Post #4 of 7 (314 views)
Re: The same Carburater for two different motors? Sign In

Thank you Hammer. I think the only potential vacuum line that isn't plugged is the short one to the front vacuum break. I used the included base gasket on top of the one I had in it to begin with. I didn't run it long enough to see if it was being flooded or starved. I am taking it off today and will check on all that. The merchant claims all carbs are flow bench tested prior to shipping. Not quite sure what that entails but I assume if it were defected that would have been revealed. My concern is if the calibration, jets or settings that make the carb a replacement for the 350 Magnum the same as a regular 350 engine.


cnewton
Novice

Jun 4, 2022, 8:09 AM

Post #5 of 7 (312 views)
Re: The same Carburater for two different motors? Sign In

Thank you Tom. I'll be taking it off today and checking a few things. If I can't find something obvious and it's still not behaving when I'm through, I will surely have more information to post.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 4, 2022, 8:16 AM

Post #6 of 7 (308 views)
Re: The same Carburater for two different motors? Sign In

Any differences in performance due to the size of the carb would be hard to see. Maybe minor differences in full throttle acceleration but certainly not a difference in idling.

There has to be some sort of fitment or installation issue to have that much effect. Something isn't matching up in the mounting most likely, assuming the choke is working properly.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 11, 2022, 4:44 AM

Post #7 of 7 (209 views)
Re: The same Carburater for two different motors? Sign In







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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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