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Need help with aq120 engine

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DAVID123

New member
In the process of buying a 1981 bayliner 19' with a Volvo penta 120. Im not 100% sure which 120 engine it is. Engine would not start when I went to look at it. We towed it to a Marine shop they installed new points/condenser. It fired up but does not stay running. Compression is 150 on all 4 cylinders. It looks like there are no parts available for this carb? Should this be as easy as cleaning the carb to get this thing running? Should I stay away? Getting the boat for $1000. Thanks for the help.
 
I would make the purchase contingent on the OHC engine running, and running well!

Look at the timing belt. Is it OK? Is it indexed correctly?
Is the ignition distributor advancing as it should be?


Next on my list would be to fully check the stern drive out!
Any water in the gear oil?
Is the drive shaft bellows OK?
Is the PDS bearing OK?



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The engine needs the carb rebuilt. Mechanic said it will only stay running if the primer bulb is pumped. Besides testing it for going up and down I have not really looked at the drive. Easy to look at oil. How hard is it to check the timing belt? Not sure what a shaft bellows or pds bearing is wll have to look it up. Thanks for the reply.
 
That’s great. Again thanks for the help. Makes me feel a little better about buying the boat. Just want to make sure I can get most parts.How do I know if this is a aq120 or aq120b? It’s in a 1981 Bayliner Explorer.
 
DAVID123 said:
The engine needs the carb rebuilt. Mechanic said it will only stay running if the primer bulb is pumped. Besides testing it for going up and down I have not really looked at the drive. Easy to look at oil. How hard is it to check the timing belt? Not sure what a shaft bellows or pds bearing is wll have to look it up. Thanks for the reply.
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Given the symptoms, I am surprised that the mechanic did not check the fuel pump!

This drive will be equipped with a "Lift-Out" unit ONLY...... it is NOT equipped with power trim!
When/if the drive is tilted up.... NEVER throttle or power up!

When you check the 30W gear oil, be sure to install new O-rings at the dip stick and drain plug!


The drive shaft bellows is the upper-most bellows. It's function is to prevent water from entering the universal shaft area.
If the stern drive has been stored in the UP position for any length of time, the bellows should be replaced!

The PDS (primary drive shaft) couples the engine's drive coupler to the universal drive shaft!
It is of fixed geometry.
Yours will be a single bearing PDS.
It would be wise to replace the bearing.


This is a main suspension fork and pivot tube geometry drive!
If your mechanic refers to a Gimbal Bearing..... it would behoove you to find another mechanic!



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Just got back from looking at the boat again. Well the guy selling it to me gave me bad info on having to pump the primer bulb to keep it running. The mechanic started it up and it runs if you keep throttling it. He told me the carb needs rebuilt. I went over all the questions everyone has given me and it all seems to be in good shape. He is gonna rebuild it for 200. And put new oil in the drive. Thanks for the help I feel pretty good about this I will keep you updated and post pictures. Thanks Ricardo
 
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DAVID123 said:
Just got back from looking at the boat again. Well the guy selling it to me gave me bad info on having to pump the primer bulb to keep it running.
I would use caution re; who you accept information from.

The mechanic started it up and it runs if you keep throttling it. He told me the carb needs rebuilt.

Make dang sure that the person who does the carburetor is familiar with the Solex Carbs!
If not, take it to someone who is!

Also, the ignition distributors on these OHC 4s are notorious for advancing flyweight operation issues.
Be sure to not only set BASE advance, but to also look closely at what the progressive and total advance numbers are doing.
Find your OEM ignition advance data (BASE, progressive and Total), and follow it to the T!
If the ignition system does NOT offer the correct progressive and total advance, performance will suffer!


I went over all the questions everyone has given me and it all seems to be in good shape. He is gonna rebuild it for 200.

And put new oil in the drive.
The stern drive should undergo a Pressure/Vacuum leak-down test.
The Pressure test must be performed with the drive oil drained.
The main drive gear, eccentric piston and prop shaft should all be rotated during the leak-down test!
The s/p drive uses 30W engine oil....... NOT heavy gear oil!


Thanks for the help I feel pretty good about this I will keep you updated and post pictures.

Thanks Ricardo
You are very welcome!
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