More AQ151C idle issues

"My first post and sorry if I&

"My first post and sorry if I'm repeating old discussions. I've been searching the forums and there's a lot of good information there.

I've got an AQ151C that idles poorly, cuts out and hunts up and down the rev range. I thought it would likely be carb related, but I had a mechanic look at it yesterday and he initially looked into the ignition circuit.

When running, we pulled out the plug leads from 1,2 and 3 in sequence and it didn't make a great deal of difference to the running of the engine, so it looked like 4 was doing the bulk of the work.

I've replaced the plugs today and ordered up a set of plug leads, since I suspect they are the originals. I also had a pop at checking the timing with a strobe and it looked like it was at 10-12 BTDC when it should be 6. Would this be enough to make it run poorly at idle or do the symptoms still sound like carbs? At speed it seems OK, it pulled 5500RPM at the weekend, it just doesn't like going slow.

I've also followed the discussions on converting the points to Petronix electronic ignition and I'm trying to source an Ignitor and Flame Thrower coil for the engine.

Thanks for any advice."

"If you are considering upgrad

"If you are considering upgrading to Pertronix, I suggest you do that first, then replace rotor, cap and wires (start with a clean slate). Also, inspect the condition of the centrifugal advance weights and springs inside the distributor. Afterwards, set the ignition timing. In all likelihood, you will see that the engine idles steady after the upgrade and new components.

Afterwards, take the time to synchronize the carbs and adjust the idle speed and idle mixture. Do a search in the forum old threads to see how."

"Thanks El. I'm trying to

"Thanks El. I'm trying to see if I can source Pertronix parts in the UK, otherwise I may need to get them sent from the US.

So you think it's more likely to be the ignition circuit than fuel? As I mentioned in the original post, sometimes the engine smooths out and speeds up when idling, but I wasn't sure if that was defective plug leads working intermittently or if it was the fuel status improving."

"Paul, I am not 100% sure of w

"Paul, I am not 100% sure of what is causing your problem. However, when you have all these symptoms and the engine is "new to you" and you are unsure of its condition and history, I think the best thing to do is to start with a clean slate by installing a new rotor, cap, leads, spark plugs and in your case an electronic ignition kit. Afterwards, you deal with carb synchronization and fuel idle mixture adjustment. Otherwise, you can drive yourself crazy replacing one component at the time."

"An update:

I ordered a Per

"An update:

I ordered a Pertronix Ignitor and Flamethrower coil and also sourced a couple of rebuild kits for the SOLEX 44 PAI carbs. Just prior to getting the parts I took the boat for a good run, two and a half hours running at 4200 RPM and it worked fine. However the low speed issues were back with a vengeance when I got back to the marine. It cut out again. The next time I tried to start it it would not start and idle, just died every time.

So I removed the carbs and gave them to a marine engineer to rebuild. He found that the accelerator pump internal lever was bent and jammed, so would never open, so at low revs or high revs, this was contributing nothing. It looks like the rear carb was supplying all the fuel for all four cylinders. One of the carbs also had a lot of water in them.

I got the carbs back this morning and before installing them I checked the fuel filter and discovered water in the fuel. So I drained the tank completely and put a few gallons of fresh fuel in then installed the carbs. Hoping for the best I fired the thing up. And it still runs like a dog. I'm going to do the Pertronix mods tomorrow and I hope this sorts the problem.

A questions about this. How do I go about setting the timing when I've installed the electronic ignition?

Sorry about the dumb questions, it's been years since I've messed about with timing!"

"Get a timing light, put the p

"Get a timing light, put the pickup coil in #1 spark plug lead. Then, set the idle timing to 10ºBTDC if you are going to use mid-grade gasoline or higher, and at 6º if you are going to use regular.

Don't forget to adjust idle speed and idle mixture, as well as synchronizing the carbs after you are donw with the timing.

BTW, it seems to me that the accelerator pump being jammed only would have a negative influence while accelerating, but not at idle."

"Thanks. Yep you are correct o

"Thanks. Yep you are correct on the accelerator pump issue. I should also have mentioned that in the forward carb there was a ring of dirt that stopped the butterfly valve from closing fully, so there was no vacuum for the idle jet to kick in.

As or the timing, I'm not sure how I go about setting this when the engine won't idle..."

"I guess you will have to fidd

"I guess you will have to fiddle a bit with the carbs and try to do an approximate synchronization as stated in the manual, which you can download from here:

http://www.volvo.com/volvopenta/global/en-gb/marine_leisure_engines/engines/out_ of_production_engines/out_of_production_engines.htm"