Gents
I have a 1985 Wellcraft Nova XL, 5.7 L, Mercruiser 260 Alpha 1
The carb is a Rochester Q-jet number 1347-8292
Early last season it was running poorly with hesitation and lagging throttle response. Then it scared the hell out of me when twice it dumped fuel all over the intake manifold. To this day I dont have a clue how. That is NOT supposed to happen on a marine engine. I assumed maybe a stuck float, but arent marine carbs designed to dump INTO the intake manifold, NOT ON IT?
I removed the carb, took it apart, cleaned it, blew it out with compressed air, checked the float level measurement (it was right on), replaced just the accelerator pump, and reinstalled it. It ran well until the end of the season with no more fuel dumps. At season's end it began hesitating again, most noticeable when starting skiers, or any hole shot where you place a lot of demand on the throttle. Last fall I decided I would rebuild, or replace it this spring. So, my questions to ya'll are...
1. I've read the blogs but I have decided to not rebuild it myself. It is very deteriorated with a lot of pitting of the throttle plates and choke plate. I would be inclined to replace it with a reman, but they seem to cost more than a new Holley or Edelbrock. If you were me, would you go with the reman Q-jet, or a new a Holley or Edelbrock, or are there other options I should consider?
2. When I research the Holley & Edelbrock sites, I cannot determine which carb would be the closest replacement for my original carb. They seem to list theirs by cfm. I have not found anything that tells me the cfm of my Q-jet. My guess is that it is around a 600 cfm. Does anyone know what he cfm of the original carb is? and which model Holley or Edelbrock would be the correct replacement for the OEM carb?
3. Then we get into the discussion of spreadbore vs quadrajet. On cars I like the quadrajet, but on boats I'm not sure that it matters. Mercruiser obviously thought the Rochester Q-jet was appropriate, so that weighs heavily on me (kinda like to keep things close to original), but boats seem to cruise at steady state more than doing a lot of accelerating like cars (at least mine does). So would it make more sense to stay with the Q-jet or switch to a spreadbore?
4. Do I need to change the intake manifold if I change carbs? Seems Edelbrock especially likes to pair their carbs with their manifolds. Clever marketing or matched set??? If so, what would be best for the 260 Alpha 1? Does this present an opportunity to up the HP a little bit?
5. I honestly would prefer to have an EFI system, but the blogs indicate it's probably better to trade boats than to retrofit a fuel injection to a carbureated engine. So I'm inclined to take that sage advice and stick with the carb unless someone has a compelling counter idea.
and finally
6. I have read nothing that says this (and dont want to start any rumors) but I'm wondering if the ethanol in the fuel these days is eating the internal plastic parts (ie, accelerator pump) of my old carburetor? If so, are today's reman'd and new carbs built better to withstand the ethanol?
TIA
Don
I have a 1985 Wellcraft Nova XL, 5.7 L, Mercruiser 260 Alpha 1
The carb is a Rochester Q-jet number 1347-8292
Early last season it was running poorly with hesitation and lagging throttle response. Then it scared the hell out of me when twice it dumped fuel all over the intake manifold. To this day I dont have a clue how. That is NOT supposed to happen on a marine engine. I assumed maybe a stuck float, but arent marine carbs designed to dump INTO the intake manifold, NOT ON IT?
I removed the carb, took it apart, cleaned it, blew it out with compressed air, checked the float level measurement (it was right on), replaced just the accelerator pump, and reinstalled it. It ran well until the end of the season with no more fuel dumps. At season's end it began hesitating again, most noticeable when starting skiers, or any hole shot where you place a lot of demand on the throttle. Last fall I decided I would rebuild, or replace it this spring. So, my questions to ya'll are...
1. I've read the blogs but I have decided to not rebuild it myself. It is very deteriorated with a lot of pitting of the throttle plates and choke plate. I would be inclined to replace it with a reman, but they seem to cost more than a new Holley or Edelbrock. If you were me, would you go with the reman Q-jet, or a new a Holley or Edelbrock, or are there other options I should consider?
2. When I research the Holley & Edelbrock sites, I cannot determine which carb would be the closest replacement for my original carb. They seem to list theirs by cfm. I have not found anything that tells me the cfm of my Q-jet. My guess is that it is around a 600 cfm. Does anyone know what he cfm of the original carb is? and which model Holley or Edelbrock would be the correct replacement for the OEM carb?
3. Then we get into the discussion of spreadbore vs quadrajet. On cars I like the quadrajet, but on boats I'm not sure that it matters. Mercruiser obviously thought the Rochester Q-jet was appropriate, so that weighs heavily on me (kinda like to keep things close to original), but boats seem to cruise at steady state more than doing a lot of accelerating like cars (at least mine does). So would it make more sense to stay with the Q-jet or switch to a spreadbore?
4. Do I need to change the intake manifold if I change carbs? Seems Edelbrock especially likes to pair their carbs with their manifolds. Clever marketing or matched set??? If so, what would be best for the 260 Alpha 1? Does this present an opportunity to up the HP a little bit?
5. I honestly would prefer to have an EFI system, but the blogs indicate it's probably better to trade boats than to retrofit a fuel injection to a carbureated engine. So I'm inclined to take that sage advice and stick with the carb unless someone has a compelling counter idea.
and finally
6. I have read nothing that says this (and dont want to start any rumors) but I'm wondering if the ethanol in the fuel these days is eating the internal plastic parts (ie, accelerator pump) of my old carburetor? If so, are today's reman'd and new carbs built better to withstand the ethanol?
TIA
Don
