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AQ120B Runs Rough

J

jjlutzel

Member
"I’ve got a 1980 22’ Bayliner

"I’ve got a 1980 22’ Bayliner with an AQ120B engine and a 270 drive. The engine was running fine until I heard a pop. It ran fine again for an hour or so, then got very rough and finally stopped. I’ve replaced the points, plugs and, because I couldn’t see a spark, the ignition coil. It starts right up, but the RPM varies wildly and it needs to be coaxed with the throttle to keep running until it gets up to full operating temp. Then it runs, but rough, with frequent popping misfires. There is no backfiring through the carb.
When I put the timing light on it the mark is steady, but when the engine misfires the timing light doesn’t ignite as though there is no spark.
My plan is to look at the distributor rotor again and maybe replace the plug wiring.
The RPM variation makes me think that it may be fuel related, perhaps water in the fuel. This engine doesn’t have a fuel water separator or even a fuel filter that I have been able to find.
Any thoughts?"
 
Remove the distributor plate u

Remove the distributor plate under the points and check the condition of the weights and the springs.

And consider upgrading to electronic ignition by installing a Pertronix or a HotSpark kit in your distributor. You will be glad you did.
 
The timing belt feels tight an

The timing belt feels tight and it seems to be running smoothly when I put the timing light on it. What else would I see if it is a jumping belt?
 
"That might be quite an operat

"That might be quite an operation as You have to remove the heat exchanger tank and dismantle the front of the engine. Then align the marks on crank-shaft gear - camshaftgear and timing wheel gear. (recommend to have a manual at hand). The belt may have jumped one toth which will give totally wrong opening of the valves compared to timing and crancshaft position. If Your belt is older than 5 years, just have it changed and very often it pays out to change the tensioner and bearing at the same time."
 
"IT IS IN THE DISTRIBUTOR, I C

"IT IS IN THE DISTRIBUTOR, I CAN BET YA. IF THE TIMING BELT JUMPS, YOU WILL DEFINATELY KNOW.SOUNDS LIKE THE DISTRIBUTOR."
 
"You gotta try a pertronix kit

"You gotta try a pertronix kit or one of the other ones mentioned here..........like hot spark. They will solve any ignition problem you have, and it sounds as if you have one."
 
I'll take the advice and i

I'll take the advice and install an electronic ignition. But first I'll have to repair a hole about the size of a peanut I found in the drive bellows. While I'm in there I'm going to replace the exhaust bellows and the water intake fitting.
 
"Drive bellows are not recomme

"Drive bellows are not recommended to be repaired, but changed.
If You have been running with water in the bellow there is a risk that the intermediate shaft bearings have been dammaged as well, they are not water sealed in any way, just a rough grease seal.
I got the feeling You should just rip out the engine, take off the intermediate housing and check/replace the bearings. At the same time when everything is easy accessable, take down the front and check/replace Your timing belt. You might save a lot in costs and time doing it 'on the hard' with engine out of the boat."
 
"Well, it may come to that. I

"Well, it may come to that. I didn’t run the engine and drive very long with the leak, however it only takes a minute to take in enough salt water to cause damage. As for the bellows, certainly they can’t be patched. Repair means replace.

The drive also makes a loud howling sound when I make a hard turn. From reading some of the other posts, it looks like that may be caused by a faulty universal fitting.

After that, on to the engine problem."
 
"The sterndrive is off the boa

"The sterndrive is off the boat and the U-joint assembly is a wreck. The Clymer manual describes the procedure to remove and replace it, and I’m a little concerned about the shims, but here’s the dilemma - I can’t tell the condition of the shaft bearing. Is there any way to tell if it is good or bad short of removing the engine and just replacing it?

The mechanics around here don’t even want to work on a 27 year old engine. Their solution is to take everything out and repower. Maybe, but that seems like a lot to spend on a 27 year old 22’ boat."
 
"Why would they even have to w

"Why would they even have to work on the engine if what you are trying to do is to install new bearings in the bellhousing? Just pull the engine with the bellhousing, replace the bellhousing bearings, put everything back together, reinstall the engine on your boat and start having fun on the water
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"What you said makes sense and

"What you said makes sense and I will go that route. I don't have the facilities to pull the engine myself, and the mechs in this part of the world are so busy that they would rather just do repower projects than a "small" job like this. They almost had me convinced."
 
"If you are mechanically incli

"If you are mechanically inclined, what you can do is disconnect the wires, fuel line and exhaust, then find any shop that can pull the engine (no matter what they are specialized in as long as they have the right hoist). If you have (or can get hold of) a pick-up truck to pull your boat's trailer, put an old truck tire on the truck box and let the engine rest on it. You should be able to pull the bellhousing just there and once you have installed new bearings and seals just put everything back together and ask the shop to hoist the engine again into your boat. No rocket science, and the operation from pulling the engine to reinstalling it can be done in a few hours (even if you have never done it before) as long as you have the right materials and tools at hand.

And if you have a friend with a crane truck, even better. That's how I pulled my engine.
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"I think that's a plan. I

"I think that's a plan. I can do that. My trailer is long gone and the boat is in a boat yard on a rack, but I can probably find someone with a hoist. In fact, looking at the picture, the yard has a hoist like that.

Thanks for the help on this."
 
"We removed the drive and repl

"We removed the drive and replaced the universal assembly, both bellows, the gimbal bearing, a seal to the housing, cooling water fitting and the cooling water hose. I put the boat in the water this morning and it ran quiet at low speed, but at higher speed (3000 rpm) it is quiet going straight, but very noisy in turns, especially turns to starboard. And I mean very noisy.

I have not replaced the shaft bearing yet.

Any ideas?"
 
"I think you have answered you

"I think you have answered your own question in the second paragraph of your message, Joe. However, I am a bit confused with your post, because what in Mercruisers is described as the "gimbal bearing", the equivalent in VP AQs is known as "bellhousing bearing(s)" or "primary shaft bearing(s)". Which "gimbal bearing" did you replace?"
 
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