Assistance needed. I have 4 questions.

J

jsenske1

New Member
Feb 14, 2009
41
michigan
Boat Info
1979 240 srv hardtop
Engines
chevy 350
Hi. I am hoping some of you could be so kind and help me by answering a couple questions. First and foremost I have a '79 SRV 24 Hardtop with merc 260 5.7L. Upgraded coil to petronix.

Questions

1. What carb is a direct replacement for the stock quadrajet? How many cfm's is the stock carb. The issue is i had this carb rebuilt twice (different mechanics) and i am still having the never ending low rpms/boat stalls at idle. This may or may not be the issue, but would be nice for reference.

2. How do i check for vacuum leaks? I have done the "ether" test around the carb with no reaction in the rpm's. Can there be a leak elsewhere?

3. Possible charging issue. How do I test an alternator? what size do i need for this engine? I had the alternator rebuilt last year (supposively) but when my boat runs for awhile and the my issue from Question 1 happens, I need to use a jumper box to start the engine. Runs fine at WOT.

4. How many fuel filters and where are they located? I know about the inline, one in the carb, but are there more? is there one on the end of the fuel line that is in the tank?

Alot of questions, but thank you in advance for taking the time to read and possibly respond.

BTW I have been dealing with this for 3 yrs!! I can't take it any longer

Jeff
 
1. The carb should be 650cfm. You can use another q-jet (obviously), an Edelbrock Performer, or a Holley Spreadbore are good replacements. The Holley would be more perf. oriented, but the Edelbrock is very easy to deal with.

2. You did what I would have done.

3. Check the output voltage on the alternator. At 1500 RPM's, it should be between 13.8 and 14.2 volts

4. You've found all the filters that SHOULD be there.

I had issues like you're describing. I unbolted the q-jet, dropped it in the river, and put an Edelbrock on. It was great after that! Seriously though, have you checked timing and all that? Are you sure the ignition system is up to snuff?
 
390x said:
1. The carb should be 650cfm. You can use another q-jet (obviously), an Edelbrock Performer, or a Holley Spreadbore are good replacements. The Holley would be more perf. oriented, but the Edelbrock is very easy to deal with.

2. You did what I would have done.

3. Check the output voltage on the alternator. At 1500 RPM's, it should be between 13.8 and 14.2 volts

4. You've found all the filters that SHOULD be there.

I had issues like you're describing. I unbolted the q-jet, dropped it in the river, and put an Edelbrock on. It was great after that! Seriously though, have you checked timing and all that? Are you sure the ignition system is up to snuff?
Click to expand...


Yes I have checked timing, dwell etc (forgot to mention that). how do i test my ignition system? you mention the carbs, do i just search for x brand and match the cfm's? is there a model q jet? thanks
 
How long have you had it? When was the ign. upgraded? Plugs, wires? A plug wire worn or rubbed through could cause a short. The carb being rebuilt twice by two people (I assume both had some trining or knew what they were doing) would lead me to believe that the problem is elsewhere. A vacuum leak sounds likely, but I don't think I would be checking with ether as you're adding fumes to a closed bilge. As flamable as that stuff is all you need is a small spark or heat source and stalling at idle will be the least of your problems. There is a way to do it with water, spray the water on the hoses and if it sputters or stalls you should be able to trace a leak from there. Another thing to think about is just because the carbs were re-built doesn't necessarily mean that they don't need to be tuned to your motor and or for weather. In colder weather a higher RPM is needed at times and may need adjustent (I remember having a '69 Firebird and messing with the carb constantly in the fall and spring as the temps changed). I would look into the timing, maybe a grounding issue with the ignition, and check again for vacuum leaks, there are a lot of hoses and it's easy to miss one. Carb and intake gaskets can leak at times too causing a similar problem in vacuum loss. Is it just at idle, or does it studder a little when applying some power? Could be the worst of all, a cracked head allowing water into the cylinder (I've seen that before too) but removal of the plugs should identify that.

Best of luckn and keep us updated on what you look through, find, and how you end up finding it!
 
Holley 4175, Edelbrock 1409, I think the q-jet is a 17059298
If you checked your ignition system (dwell, timing, etc.), I don't know what else I'd tell you to test. When I've had coils go back, I can't rev it up, but it'll idle fine. I've also had engines die because of charging issues too, so you definitely need to make sure your alternator is working right.
 
the problem only occurs at idle i.e trolling. I can troll for about an hour then the problems begin. Temp is fine, plugs wires, etc where changed last year. The boat idles at 750-800 while engaged. Thats why i am now leaning towards the charging system. I love the boat, motor has only 350 hrs on it. The only filter i havent changed is the one in the tank..assuming i can get to it. i have searched the site and have tried all the suggestions as to the air/fuel mixture screws..about 2 1/2 turns out. Again runs great on plane, after trolling, i want to sink it!!! I have to use the jumper box each time it stalls after awhile.
 
also, it seems to stall each time i only have one other person and we have a fish on!! tangled mess.
 
jsenske1 said:
the problem only occurs at idle i.e trolling. I can troll for about an hour then the problems begin. Temp is fine, plugs wires, etc where changed last year. The boat idles at 750-800 while engaged. Thats why i am now leaning towards the charging system. I love the boat, motor has only 350 hrs on it. The only filter i havent changed is the one in the tank..assuming i can get to it. i have searched the site and have tried all the suggestions as to the air/fuel mixture screws..about 2 1/2 turns out. Again runs great on plane, after trolling, i want to sink it!!! I have to use the jumper box each time it stalls after awhile.
Click to expand...

Def. sounds like an altenator to me! I'm not too sure if they can be tested off the vessel or not, but that sounds like it! At higher RPM's it is giving off enough juice to maintain, after that (idle speeds) it is running off the batteris(s) and when they die the boat dies.
 
Great..I will see if they can test the alternator out of the boat. If it is bad am I better off buying a new one or have this rebuilt..again? Should i increase the size of the alternator? thanks for the help.
 
Depending what it costs to rebuild, you can buy a new one from dbelectrical.com very cheap. I'm sure it's probably Chinese, but I got several good years out of one of them on my last boat. It's probably still running strong, but I sold the boat.
 
A quick test is to turn the key to "on" and look at the volt reading, 11.5 eg, now start the engine, voltage should be more than what you started with 14.5 eg.
 
I had a problem like this on a cobalt years and years and years ago. It would charge fine until low RPM, then it would stop charging and begin to discharge. This boat didnt have a voltmeter but an ammeter guage which made it alot easier to know if you were getting a charge or not (before it may be too late that is). Rebuilt the alternator and problem solved.
 
jsenske1 said:
Great..I will see if they can test the alternator out of the boat. If it is bad am I better off buying a new one or have this rebuilt..again? Should i increase the size of the alternator? thanks for the help.
Click to expand...

Where are you at in Mi? There is/used to be a lil ma' and pa' shop here that rebult starters and altenators and they were dirt cheap. $5 to re-build a starter and if it were a common one like say a Chevy 350 they would just take your $5 and give you one already done on the spot! I can look and see if they are still there, last I knew the daughter was operating it (but that was 3/4 years ago) so it very well may be! There's a lot of lil lakes around here so they may even stock what ou need.
 
Acb4boss said:
Where are you at in Mi? There is/used to be a lil ma' and pa' shop here that rebult starters and altenators and they were dirt cheap. $5 to re-build a starter and if it were a common one like say a Chevy 350 they would just take your $5 and give you one already done on the spot! I can look and see if they are still there, last I knew the daughter was operating it (but that was 3/4 years ago) so it very well may be! There's a lot of lil lakes around here so they may even stock what ou need.
Click to expand...


i am near kalamazoo
 
So I had my newly rebuilt alternator tested today and guess what.....Not working! So what is the difference between marine and auto alternators? Are marine sealed? what size should i go with? thanks
 
Marine alternators are ignition proof. DO NOT USE AN AUTOMOTIVE ALTERNATOR!!!!!!!!!:grin:
 
i knew it had to do with something withthe vapors/sparks. I was just curious to know if the internal workings where different. Should i upsize the amprege? What is the difference between single wire and 3 wire? will a single wire work on one that is 3?
 
I don't think the internals as far as the windings are any different. As far as upsizing, I'd doubt you'd gain anything by upsizing. Get a 3 wire. One wire alternators need to be revved to a certain rpm before they start putting out power, and I think they cost more money anyway.
 
I just went to get the part # of the alternator and wouldn't you know it..its unreadable! anyone know what part # for this 79 350 5.7l?
 
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