AQ151 pinging after Carb rebuild

[CSCstull]

I have a VP AQ151. 1980's? I just rebuilt both Solex carbs. Before the rebuild when I could get the motor started it idled fine and would bog down at over 1/2 throttle but at idle it ran smooth and clean.
I just put the newly rebuilt carbs on: (The accelerator pumps were full of corrosion)
1) I loosened the bolts on the linkage to re-set the butterflies to closed.
2) advanced the linkage to just make contact with the valve arms, and re tightened the linkage bolts.
3) Bottomed out the set screws and backed out 8 turns.

Motor kicks over without me applying any gas. But now I have knocking and any amount of throttle and I get bad backfires.

I've spent the last two days wading through internet forums and I cannot find an answer.

Next I know I need to verify the timing. I cannot for the life of me find any pictures that reference timing marks I have attached pictures of what I have to work with.

 

[Don S]

Re: AQ151 pinging after Carb rebuild

Go to the link below, and download the owners manual for your engine. It has all the tunup specs in it
Publication search - Publications / Manuals : Volvo Penta

There should be a notch in the pulley for TDC, you just use a timing light and turn the distributor to get your timing (6? BTDC @ 850rpm)

 

[CSCstull]

Re: AQ151 pinging after Carb rebuild

Went out to do a static timing setup on the motor and it wouldn't turn over. The starter sounded good, so then I used a circuit tester light to trace the gremlin. Ended up being my ignition coil was shot. $40 at Napa, installed it, motor kicked right over! Still getting bad backfires and pinging. So......
I decided to verify all the timing settings on the motor. So I pulled everything off of the front. I found more issues.... You can see where this is going.
- All of my timing marks were lined up perfectly. (WIN)
- Bad leak from my sea water pump, but I can fix it. When I bought the boat, it came with two spares. Now I know where the water in the bilge was coming from!
- The previous owner(s) had sheared off the lower thermostat housing bolt head. Now I know where my coolant was going! Easy fix! (Win) :grumpy:
- Previous owner(s) had an ammo can full of spare parts etc. There are numerous spare gaskets and o-rings to replace everything that I have removed. So I will ensure all new gaskets and seals for re-instalation. (Win) :joyous:
- I went to remove the distributor cap to ensure no moisture, clean points, etc. THIS IS WHERE MY ENGINE ISSUES ARE! I broke both screws when trying to remove the distributor cap because they were coroded and welded to the housing. Still there after a 2 day soak. :facepalm:
There was no gasket or o-ring between the cap and housing. (I just realized I found the o-ring when removing the heat exchanger and everything off of the front of the motor.) This allowed salt water and moisture into the housing. There was physical salt and a lot of it built up in side the housing along with visible standing condensation, and the points all had a nice layer of green corosion on them. I ordered the Hot Spark EI system and should be here on Wednesday.
- Timing belt has less than 50 hours on it and looks in very good condition.
- The main wire harness has a lot of corrosion in most of the points, went to Radio Shack and got a kit to rebuild it for $8.
- I cleaned every electrical connection inside the engine bay that I could get to and used battery terminal protectant spray to seal everything from corrosion.
- Upper drive unit started leaking over the winter. Rebuild kit was supposed to be here on Saturday and never showed, so I will be pulling that and rebuilding it as well and all ready bought new u-joints to install while I am in there.

I'm the third owner of this boat, I've owned it less than a year and it ran ok by my standards last year for salmon and crabbing. I was able to get it up to 24 knots based off of my Garmin GPS 76. The original owner kept and has passed on all paperwork with the boat including the order forms when he bought the boat brand new from the GlasPly factory, including all oil changes, when he swaped the motor out and upgraded it to the AQ151, etc. I talked in length to the second owner who I purchased the boat from and he owned it for 4 years and only put about 5 hours on counter. He didn't do any work on it besides adjusted one carb and put two new batteries in it before he sold it to me.

 

[Don S]

Re: AQ151 pinging after Carb rebuild

You need to set the timing with a timing light to stop your pinging problem.

 

[CSCstull]

Re: AQ151 pinging after Carb rebuild

Hot spark installed, All timing marks were 0deg. TDC, started motor, used timing light, set to 6 deg as per manual, still getting pinging sounds like from #3? Spark plugs?

You need to set the timing with a timing light to stop your pinging problem.