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robj
06-04-2009, 03:53 PM
"Hello,

This problem has been nagging me for the last 2 years. Engine runs great upto about 4000 rpm and above that is starts to bog, stumble. Any suggestions? I have done all the obvious, carb rebuild, compression is good, new plugs, fuel pump, Pertronix unit. Still can't figure it out.

Thanx for your suggestions and have a great day

Rob."

el_pescador
06-04-2009, 04:01 PM
"Here are some more items for your list:

Coil, wiring, ignition switch, kill switch, anti-syphon valve, water in fuel, carb fine strainer, accelerator pump stuck or out of adjustment, Pertronix gap, ignition wires...."

robj
06-04-2009, 04:06 PM
"That was fast!!! Have done the above, new anti-syphon valve, complete carb overhaul, including new pump and checked the screen. Have not checked the pertronix gap. Don't have the plastick gage with me, but does anyone know the gap? Will try setting it with feeler gages. Time to go for a below 4000 rpm cruise. Don't run it that high anyways except when accelerating.

Thanx for your help and have a great day

Rob."

el_pescador
06-04-2009, 05:11 PM
"Rob, the gap is 0.030. Also, check this link regarding how to adjust the dwell with a Pertronix module, you will find it interesting.

http://www.ratwell.com/technical/PertronixAdjust.html ("")

Also, remove the flame arrestor in the carb and make sure the accelerator pump squirts all the way from idle to WOT position. If it stops squirting at mid-range throttle position , that could be your problem."

am_dew
06-04-2009, 05:56 PM
Thanks El...that is an interesting article about dwell with the Pertronix. I always wondered how critical that gap was and it sounds like the larger the gap the better as long as you don't risk bumping into the distributor body.

robj
06-04-2009, 09:55 PM
"Thanx ElP for the info. I guess I wasn't very specific, stumbles is rather vague. What is happening, it will rev up to 4800 rpm no problem, then it will start to stumble, drop to 4200 then 4400. I am quite certain it is not the accelerator pump. Could be starvation for fuel or ignition related. It seems to have no power above 4000 rpm.

Thanx again

Rob."

robj
06-05-2009, 09:38 AM
"Hello again,

This problem can also be caused by fuel starvation. Everything from the tank forward has been changed/rebuilt. How does one clean the pick-up tube in the tank? That could be the problem.

Thanx and have a great day

Rob."

el_pescador
06-05-2009, 10:26 AM
"Robj, in some fuel tanks you can access the pick-up tube and remove it, but in some others (mainly aluminum tanks) it is welded and cannot be removed. If it can be removed in yours, then remove it and see if there is a strainer attached to the end, which most likely will need some attention. If there is no way of removing the pick-up tube, then you may have to backflow it with compressed air at very low pressure. But before you go that way, make sure the tank fuel vent is working correctly to prevent overpressure. Removing the filling cap should also help.

Also, have you tried the ol'e trick of connecting a jerrycan to the fuel pump and run the boat at high RPM to see if fuel starvation is the problem?"

robj
06-05-2009, 03:30 PM
"Thanx ElP,

My tank is plastic, will take a look at the strainer later. Unsure how it is removed, but I will check it out. Thought of the air pressure idea but removing it to clean is probably the best option. Since this problem only happens at high rpm, under load it is something that cannot be diagnosed in my driveway on muffs. I did not bring an auxiliary tank with me. Might have to wait until I get home. If I can, I will probably remove/disable the strainer since I have a water seperator/fuel filter installed. That will pick up any contamination.

Have a great day

Rob."

el_pescador
06-05-2009, 04:24 PM
Make sure you also check that the vent overboard is clear. I have seen aluminum vents with SS screen choked solid.

robj
06-05-2009, 05:01 PM
"Thanx ElP,

The vent seems to be OK. I can see the fumes coming out when I fill the tank. Regardless, thanx for the point and I will check it. Do you have an idea if the pick-up tubes are removable on a plastic tank. My biggest fear is trying to remove the tube and damaging my tank, having to remove it, cut the floor etc.

Have a great day

Rob."

el_pescador
06-05-2009, 05:52 PM
"Rob, I am not sure right now, but the last plastic tank I installed a few years back was a Tempo and I don't recall the pick-up line being removable (at least, not easily)."

robj
06-06-2009, 12:34 AM
Thank you again ElP. Will check it out when I get home. Just about time to go and catch the big ones!!

Have a great day

Rob

ruckus3313
06-08-2009, 12:42 PM
"I believe most of the plastic Moeller brand tanks have a removable pick-up feeds into them, however, i'm not 100% positive."

robj
06-08-2009, 01:08 PM
"Thanx for your reply. I am back home and will post pix of the pick-up fitting at the top of the tank tonight. It does look removable, just not sure if it is a bulkhead fitting or not and how best to remove it.

Have a great day

Rob."

robj
06-12-2009, 01:14 PM
"Hello again,

I blew out the fuel pick-up line. Did not remove it from the tank, but drained the fuel, removed the sending unit, removed the fill cap, and the anti siphon valve and went at it with compressed air. If there was any blockage, that definitely cleared it up.

My neighbour mentioned that my problem may be caused by excessive play in the distributor shaft. There is some play in mine, but not alot. How much, if any, is acceptable? I am also running the Pertronix unit. Should I try increasing the gap?

Since my problem only shows up at higher rpm, and under load I don't know if blowing the fuel line rectified the problem. I am looking at all the potential causes, fixing them and hoping the problem is fixed on my next outing. That is why I am asking about the distributor.

Thanx again and have a great day

Rob."

el_pescador
06-12-2009, 01:47 PM
"Rob, the first thing I think you should try is a test run and see if the problem has cleared.

Regarding play in the distributor, I think you would need quite a bit of play to have a problem, in which case the Pertronix sleeve would probably be rubbing against the module. It probably won't hurt increasing the gap, but you may want to read this before going that way.

http://www.ratwell.com/technical/PertronixAdjust.html ("")"

robj
06-13-2009, 10:55 AM
"Thanx ElP,

I read that link and when the Pertronix unit is set-up according to the install instructions, the dwell measured was 54 degrees. My service manual calls for 62 +/- 3 degrees. That is quite a difference. So maybe there isn't enough dwell time at the higher rpm's to generate a strong enough spark? Also in the report it says that by increasing the gap to 2 mm, dwell increased to 58 degrees. So I will try increasing the gap and see how that works. Have not been able to find the dwell spec for the 2842, looked all over the Pertronix site but no luck.

Have a great day

Rob."

el_pescador
06-13-2009, 11:22 AM
"You can contact Pertronix either by phone or by e-mailing them your question. They created the creature, so they should have the answers. http://www.marineengine.com/discus/clipart/wink.gif

http://www.pertronix.com/support/default.aspx ("")"

robj
06-13-2009, 11:35 PM
"Thanx again ElP.

I sent Pertronix a note. I widened the gap between the pick-up and magnets. It is over 1 mm, probably around 1.5. Started the motor and checked the timing. It was at 16 deg BTDC, I know with the old gap setting it was 6 degrees. Set the timing and checked the dwell, there is now 56 degrees of dwell. Not sure what there was before. So maybe there was not enough time (dwell) to fully charge the coil at higher rpm's? I will find out tommorrow, have my fingers crossed

Have a great day

Rob."

robj
06-17-2009, 11:40 PM
I exchanged a few e-mails with Pertronix and below is the last one. I am currently running a 0.049" gap so hopefully it should be OK. In my case I am positive that increasing the air gap changed my dwell. The gap I have now I have a little more dwell than spec for the Ignitor. Hope to try it this weekend.

Have a great day

Rob.


The spec for 4 cylinder Ignitor kits is 50-54 degrees of dwell. The gap between the Ignitor and magnet ring can be anything between .005”-.065”. The air gap doesn’t normally change the way the Ignitor works. It fact most of the time changing the gap doesn’t change the dwell. It’s not like a set of points in that matter. But it does have the possible of changing the dwell but normally this will not change the way the engine is running.

robj
07-06-2009, 10:00 AM
"Hello again,

Update time

Well I ran it for the past week, and still the same. Runs fine below 4000 rpm and stumbles above. Have tried everything, I think it is now time to find a good VP mechanic. At my wits end on this one.

Have a great day

Rob."

dann
07-27-2009, 01:35 AM
"I have a AQ120B engine and it is having the same symptoms; my problem is definately fuel related, when I lose power all I do is squeeze the fuel bulb (came with the boat) several times and it will hold high RPM's. I am going to inspect the fuel tank pickup and see if that is the problem."

robj
07-27-2009, 03:19 PM
"I have checked the pick up and the fuel pump is only 2 years old. Will be taking it out next week and see how she does. If not, then maybe it is Weber time this winter, that is if I keep the boat. Wife is getting 2 foot itis. We need a bigger boat. Can't argue with that!!

Have a great day

Rob."

el_pescador
07-27-2009, 03:34 PM
"Robj, regarding 2-footitis, make sure you have deep pockets. And please, don't ask me why I say that.....http://www.marineengine.com/discus/clipart/wink.gif"

robj
07-28-2009, 03:30 PM
"Just went through the carb, again. There is only one screen, right? It is the cylindrical one.

My pockets are about as shallow as they come, pretty well non existent. If I do go that route, I will buy a junker and rebuild it. Takes alot of time, but at the end I am left with a boat that is good as new. That is what I did with this boat. It was so rotten that it had dandelions growing in it. Now it is like new, probably more solid since I beefed up the stringers and motor mount. Got rid of the wood block and used a piece of aluminum angle iron through bolted to the stringers. Except for the fact that the engine does not like to run above 4,000 rpm. But these little 4 bangers are pretty cheap on fuel. Can run a whole weekend on a tank of fuel. Just takes me longer to get there. Bet you can't say that about your V8?

Have a great day

Rob."

el_pescador
07-28-2009, 05:01 PM
"You are right, Rob: I can't say that about my V8. But have you forgotten that my previous boat was a 17.5' Double Eagle with an AQ140? http://www.marineengine.com/discus/clipart/biggrin.gif"

robj
07-28-2009, 05:55 PM
"Hello ElP,

I know. You once had little power and went to big power.

Have a great day

Rob."

el_pescador
08-11-2009, 05:50 PM
"Not sure it that was the right move, though....http://www.marineengine.com/discus/clipart/wink.gif"