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About to give up - can't keep engine running

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About to give up - can't keep engine running

Old 11-26-2010, 10:47 AM
  #41  
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Originally Posted by Local Motion View Post
Fuel puking out the carb throat could = reed.

The reed also would explain the lack of fuel to continuously run, as the fuel pump diaphram needs the alternating pulse to operate.

good point - this also may have merit if you get good flow through the system manually

if fuel gets spit back out the carb when it starts thats it
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Old 11-26-2010, 12:23 PM
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When I bought the boat, the seller gave me a DT75 shop manual. Has an exploded diagram of the carb.

Well, I took the top carb off and took the float bowl off. The carb looks to be pretty clean inside, and the float didn't look obviously out of adjustment. Here are some pics:

This is the float bowl removed. Its actually pretty clean inside, and the gasket is new, so I guess the mechanic actually did take this apart and clean it:



This one is the how the float was sitting without any adjustment. The shop manual says the float height should be 0.69-0.77" measured from the top of the "nozzle" as they are calling it. However, to achieve this measurement, the float definitely wouldn't be sitting level when it was upside down (I thought I remembered reading somewhere that it was)


The only thing that seemed out of the ordinary was the pilot jet. Its broken on the outside of the carb. I tried to get a pic, but my camera doesn't do well with close up shots. Looks like it was meant to have a slotted screwdriver turn it for adjustment, however the slotted area has broken away on one side.



I haven't done anything at this point other than remove the float bowl, all the adjustments are as they were when the carb was removed. I haven't taken out any nozzles, valves, or jets. This shop manual is surprisingly sparse on carburetor rebuild information, so I don't know where the idle jets are or anything else I am supposed to clean out is. I'm going to get the Clymers manual back from the library tomorrow.



Here is also something I forgot to add, and I feel stupid for forgetting to add it.

I mentioned that I'd had the carbs rebuilt twice. Well the first time it was done, when I got the boat back, it would run pretty strong, but only with the choke closed.

I ran it for 30 seconds that way, and it sped up and died 5 seconds after I opened the choke.
I ran it for 5 minutes that way, and it sped up and died 5 seconds after I opened the choke.
I ran it for 15 minutes that way, and it sped up and died 5 seconds after I opened the choke. (Let me tell you how annoying it is to sit there for 15 minutes pushing that key in)

So, I talked to the mechanic about it, and he said the carbs probably picked up some junk and he rebuilt them again. And here we are.

If you need any more info, or more pics, or have any ideas so far, I'm all ears. I'll go pull a plug in a minute too. I really do appreciate all the help so far guys.
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Old 11-26-2010, 12:54 PM
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Again, not an expert.

Is that white powder/corrosion on the inside of the bowl?

On my Honda I removed the needle above the float and cleaned the tip.

Good luck!
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Old 11-26-2010, 01:28 PM
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After viewing those pictures it looks like you got new gaskets and little else. Make sure you have a good fuel filter like a racor ahead of your motor and go through those carbs yourself. Remove the float and use compressed air or carb cleaner with that red straw to blow out all the little passages and jets. This will not change any adjustments, just reassemble the same way. Don't pass wires or other foreign objects through the passages. Pretty darn clean inside would resemble new parts and thats not what I am seeing. Maybe its the pictures but it looks crusty to me. Do one carb at a time. It could be lots of things but your choke scenario suggests a lean condition likely caused by a clogged passage or needle valve.Good luck and keep us posted.
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Old 11-26-2010, 01:34 PM
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Will do, thanks for all the advice. It does appear to have white corrosion inside, I suppose I was expecting to see a lot worse, but what I have is worse than I thought.
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Old 11-26-2010, 01:35 PM
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Certainly sounds like a carb issue but have you tried to pump the primer bulb to keep it running?

Maybe it is just the lack of focus in the first pic but the bowl doesn't look all that clean now and certainly looks corroded as if there was water sitting in there at some point. . If the rebuild didn't include soaking the carbs (or ultrasonic cleaning) then they should have that done. That is not clean!
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Old 11-26-2010, 01:52 PM
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If it ran ok with the choke closed, EVERYTHING is ok right up to the carbs, and the problem is inside the carb itself,, Sounds like the metering jets are plugged, or the floats are way out of adjustment... Take the needle valve thats on or under the float off, shoot some carb cleaner through the jet the needle sets in.. You should get a strong spray into the throat of the carb. If not, its plugged up..
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Old 11-26-2010, 02:06 PM
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Is this your carb?

http://store.brownspoint.com/DT75/fig004-758897.asp


Clean those needle valves and I bet it runs.

How about those two fuel lines? Part#27 Replaced?
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Old 11-26-2010, 02:41 PM
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Will do guys. I don't think its the pics - I mean the pics are bad, but there is definitely corrosion or something on the carbs. (I just didn't know what I was looking at.)

And Cedarholm, no, I haven't replaced number 27, so I will be soon.

When I soak the carbs, could I soak them in one of the gallon pails of carb cleaner you can get at Autozone, or is there something else that should be used?
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Old 11-26-2010, 02:51 PM
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Originally Posted by Gas Giant View Post
Will do guys. I don't think its the pics - I mean the pics are bad, but there is definitely corrosion or something on the carbs. (I just didn't know what I was looking at.)

And Cedarholm, no, I haven't replaced number 27, so I will be soon.

When I soak the carbs, could I soak them in one of the gallon pails of carb cleaner you can get at Autozone, or is there something else that should be used?

I don't think you need to soak 'em. No expert tho.

I'd just take the bowls off and spray the heck out of the all the brass inside and spray up thru the passage where the needle valve sets. Could even 'back spray' from inside carb throat. Gotta clean a path for gasoline in float to get up into carb throat.

Deep Creep or Carb Cleaner.

Overall, just sounds like some junk particles got loose and are blocking gas flow thru needle valve and nozzle. You can remove them, just remember how many turns to remove.

Esp clean #8,9, 11.

Last edited by cedarholm; 11-26-2010 at 04:43 PM.
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Old 11-26-2010, 04:33 PM
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Try running off an external tank.
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Old 11-26-2010, 04:54 PM
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He is on an external tank. If fuel is running out the float is not set, or possible reed valve damage. Did you check the reed valves for cracks or proper seating when you had the carbs off? If you didn't already replace the spark plugs they could be fouled from all that fuel dumping in. They do have a 1 gal. can of cleaner at napa you can soak those carbs in to clean them, you may as well take them apart and do them yourself you are already halfway there. Here is a stupid question, I can't tell from the pics if the little clip that holds the float valve to the float bracket is there, does the float vavle lift when you lift the float? Or maybe that thing is upside down?
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Old 11-28-2010, 02:08 PM
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Ok, here is the latest.

One at time, I pulled each carb off. I cleaned the heck out of it, and sprayed carb cleaner down each jet and passage. Each one was free and clear, and the carb cleaner sprayed through nicely. I cleaned off the needle valves on each one, and I set the floats for the proper height per the Clymers manual. Put the carbs back together, and reinstalled them. (Carb #2 had the float setting way off; the other two were within spec)

I also took off each fuel line and blew a bunch of carb cleaner through them.

Went to start it, and nothing has changed. At first, it would fire up, and run if I had the choke closed. When I opened the choke, it would speed up and die. One one occasion, I was able to close the choke and it stayed running. Opened it again, and it sped up and nearly died, but I was able to close the choke again and it stayed running. I did that twice; the third time it died anyway.

I should also mention that it actually ran worse now than it did before. After several attempts to start it, I couldn't even get it to sputter - just cranking with nothing happening. I had my brother check the spark at the spark plugs while I was cranking it; I had spark.

I also attempted to start it using a cheap clear fuel filter, made no difference.

The reed valves didn't appear to have anything obviously wrong with them. My camera is too crappy to get a pic of them.

At this point, I am baffled. I've worked on all kinds of engines, from flatheads, to Edsels, to SBC's, to LS1 Vette engines......never had one that completely baffled me; I always had an idea of where to turn next.

I'm basically looking for what I should look for next. Its got to be a fuel related problem since I have spark, but I don't know what else to check for. I was using fuel from the same portable tank on my brother's boat; his boat ran perfectly this morning on that very same gas.
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Old 11-28-2010, 02:16 PM
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try elevating the tank higher than the motor-- [gravity feed --let us know
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Old 11-28-2010, 04:02 PM
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I've been following this post because this sounds like something that happened to me and I know how frustrated you must be. I am not a marine expert but if I were you I would go out and purchase brand new carbs, hook them up and if these don't fix your problem you can at least rule out that it's a carb issue.

I don't know how much new carbs would cost but I know when things like this happen to me I just start replacing stuff with new. I had a intermittant problem with one of my twin 225 Evinrudes where the engine would either start right away, or I would have to crank it forever. I mean forever like for an hour while the other engine was idling and charging the batteries. I had tons of suggestions and tried them all. I even had a mechanic come to my dock but of course I couldn't get the engine to act up.

I had carbs rebuilt, replaced fuel lines, replaced fuel pump....you name it and I tried it. I had an old guy tell me to replace the "brain" to at least rule out an intermittant electrical or brain problem. I have no idea what was wrong with the brain but the engine never did it again once it was replaced.

Good luck getting it figured out.

Russ
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Old 11-28-2010, 04:30 PM
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I was Googling for ya...see you're on other sites too.

Link and sync? Sounds reasonable.

Did you replace all those narrow fuel lines connecting the carbs?

So you say it runs OK when choked and surges and dies when choke open?

I'm guessing you're getting too much air, therefore too lean, when choke is off.

You'll get this...hang in there.

New plugs with proper gap?
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Old 11-28-2010, 04:38 PM
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http://forums.iboats.com/showthread.php?t=139358


http://forums.iboats.com/showthread.php?t=139904
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Old 11-28-2010, 05:09 PM
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I'm not really sure what lync and sync is....can anyone tell me? The Clymers manual lists balancing, but no mention of lynch and sync.

I didn't replace the smaller fuel lines; but I did clean them out pretty well with carb cleaner.

I agree on the lean condition/fuel starvation issue, but I can't seem to find a cause for it.

The plugs were replaced when I had the carbs rebuilt the first time. I can't remember what I gapped them to but it was per the manual. Although they looked a little wet from a lot of cranking with no fire, they didn't really look bad.

I think Brownspoint listed the carbs around $600 a piece for new ones - I definitely can't afford 3 new carbs right now!
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Old 11-28-2010, 09:03 PM
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As Cedarholm stated, when you close the choke it runs, idles I assume but when you throttle up which probably opens the choke plate it sputters and dies which means too much air as stated before.

If it is able to idle for a period of time with choke closed, try spraying some WD40 or similar product near the base of the carb and the butterfly bushing for the choke while in idle and note any differences in speed or if it dies while spraying.

I too have played with many car motors and did have two carbs that had vacuum leaks at the butterfly bushings that caused motors not to idle and run like krap. All the rebuild kits in the world didn't help that situation. There is a separate rebuild kit to replace those butterfly bushings but cost outweighs getting new carbs.

Good luck, just trying to throw out some ideas for you.
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Old 11-28-2010, 09:26 PM
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Originally Posted by Gas Giant View Post
I'm not really sure what lync and sync is....can anyone tell me?
I'm pretty sure that what that's referring to is the "synch" of the carbs, which you have already done, and the "link" just refers to making sure the linkage is in proper mechanical adjustment and operates all three butterflies equally as the throttle is moved through its range. JMO.

About the vacuum leaks at the butterfly bushings, etc, that good life mentions, I too have seen that occur with (automobile) carbs, but every one of those was a very high mileage carb, which probably doesn't apply to these. Not saying it couldn't be, and the spray test is a good, easy idea, but don't think it's too likely.

Air leak somewhere still seems like a good bet but damn, you've covered most of the likely spots.

Also, earlier you said you "knew" you had spark, since your brother (cousin, whoever) had watched at all the plugs while checking. Yes, you know you had a spark, but was it a good spark? You know as a mechanic that a spark can look "sparky," but not be strong enough to do the job. Might be worth another look at the plug wires and the high voltage system, brain, whatever that motor uses to create it, to make sure you are getting a hot enough spark under load and advanced throttle. I'm reaching here, but there aren't too many options left. Good luck.
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