Need Engine Diagnosis Help BAD!!!!

[NautiqueJared]

I have had one **** of a bad string of luck this year and I'm ready to get my boat running so I can get back on a weekly routine. I just got a call from my boat mechanic and he can't figure out what is wrong with my boat and he's giving up.....so I'm in desperate need of some help trying to diagnose this engine problem.

I have a '92 BFN with a 454 Vdrive, carb. and a coil pack. I can start the engine just fine and it will idle and even run the boat at low rpm's but as soon as I start to throttle up it bogs down and starts backfiring through the carb. I've pulled the alternator, changed the fuel pump, changed the fuel filter, new plugs, new plug wires and we even tried hooking up an external tank to bypass my tank to eliminate those possibilities.....nothing has worked and it's still not running right. My mechanic said he pulled the carb. apart and didn't see anything out of place or messed up. I have no real mechanic knowledge or experience but it seems like a lack of fuel problem. My mechanic felt like he thought it was an electric/spark problem and his lack of knowledge of the coil pack distributor setups left him unable to finish the job.

If anyone has any clue what could be wrong, please shoot me your ideas.....I'm all ears at this point.

[Mikeski]

RE: Need Engine Diagnosis Help BAD!!!!

http://www.skidim.com/prodinfo.asp?number=RK107025A

[Fly100]

Re: RE: Need Engine Diagnosis Help BAD!!!!

http://www.skidim.com/prodinfo.asp?number=RK107025A

No idea if the above kit is required to sort your fault.However I can say I have bought one of these kits and they are very good and my 196 runs a treat now.

FLY

[MikeC]

RE: Re: RE: Need Engine Diagnosis Help BAD!!!!

The carburetor backfire is caused by four possibles problems.
1. The ignition timing fires the spark before the intake valve is closed. (The distributor timing is very far off or the wires to the spark plug are in the wrong order or arcing is occuring between wire or posts on the cap.)
2. The cam timing has the intake valve open at the wrong time. (The belt or chain has slipped.)
3. The intake valve is leaking badly. (Cracked, burned, bent, or very far out of adjustment intake valve)
4. The exhaust valve on one cylinder is not opening, (damaged valve train on the exhaust side with the intake working normally.)

I'd buy the kit Mikeski gave the link to and find a good (i.e. different) mechanic to install it.

[NautiqueJared]

RE: Re: RE: Need Engine Diagnosis Help BAD!!!!

I'll give the order of events to see if my misfortunes have had anything to do with my problems as well. My first trip this year resulted in an open flush kit valve and I overheated the engine as I limped it back after discovering what I had done. I replaced the impeller and thermostat gasket and cleaned the rubber out of the lines. The next time I took it out (with a brand new prop) my friend hit a stump under the surface at lake granbury.....it was running great right before that incident. After getting fixed for three weeks I got it back and took it out to have the thing start to bog down under load before I could get to 3k rpm's. I took the alternator off and had it tested and sprayed a bunch of carb. cleaner.....took it out for July 4th and it ran fine. Since that weekend it has started to bog down again. One of the trips, I had it bog down on me so we floated around and attempted to drink a 4 hour beer supply in an hour and when we started to creep our way back to the dock, I gunned it and it accelerated fine so we pulled a couple riders and then I started having a problem with the ignition breaker popping. I messed with one of the inline fuses behind the dash and I haven't have a problem with the ignition breaker anymore but I haven't have it run right either.

I appreciate the feedback so far......

[Quinner]

RE: Re: RE: Need Engine Diagnosis Help BAD!!!!

Did the Big Block Chevy's also have the Pro-Tec ignition? When the Pro-Tec was starting to fail on my 93' w/a 351 Pro Boss the symptoms were:
Once warmed up it would not start until it cooled for a while and also backfiring/missing/popping at the higher RPM's. Some times no issues at all?
Installed the kit Mike referenced above and no more problems.

[Spyfunkr]

RE: Re: RE: Need Engine Diagnosis Help BAD!!!!

I had the SAME problem on my 94 Nautique Ford 351, holley 4 barrel... not sure how close yours isThere is a gas inlet fitting with a screen in it right at the carb. That had tons of sand bouncing around in it the screen barely let light thru. Cleaned and problem solved. Of course, now I have a new problem, with new symptoms.

Chris

[apexrig1]

check the oil plug for metal filings. Maybe a cam lobe is gone or on its way out. Take the valve covers out and see if they are all moving the same.

[NautiqueJared]

I finally got the distributor kit installed on my '92 BFN and afraid to say, I'm still having problems. I'm looking for more suggestions but am still going to explore the suggestion of a filter screen in the fuel line. The boat just doesn't seem to have any power. It isn't backfiring at low speeds anymore, only when I am trying to run the boat at full throttle. I took it out the day after I picked it up from the shop and was able to pull everyone without too many problems and the only real problems were when I was throttled up going back to the dock. I took the boat back out this past weekend and seemed to be running ok but after we filled the sacks and went to test the wake to adjust weight, we couldn't get the boat to power up enough to plane out. I figured we had too much weight in the boat so we just emptied most of the sacks and tried again with the same results. It seems like timing could be off a little cause it seems to be loping more than usual.

Any other suggestions other than timing and maybe the fuel filter screen?

[skiinxs]

As mentioned earlier in one of the posts, cam timing can cause this. On an older Ford I have seen the nylon gears wear causing the timing chain to become loose. Started with a tuneup and the distributor timing was off. Adjusted it and a few days later, same thing, dist timing off. After going through this cycle a couple of time I realized that it was jumping time on the cam sprocket, causing the cam and distributor to be off. Even with corrections to iginition timing it got to the point that the cam was so far late that it starting back firing through the carb. If you have reset the distributor more than once, I would check that.
Dave