volvo aq125. backfired then died any suggestions

[madridbruce]

Hey fellsa hows things. im not too happy with volvos set up. the boat is not reliable. i was out on the ocean , at 4000 rpms, i felt alot of vibration in the boat. a loud backfire and loss of power , reset the timing 15 btdc, 1 pistion tdc, lined up 2 timing marks , did not start. spark plug was bone dry when i pulled it , dont know which direction to go carb, gimbal bearing , timing again, all the above. thanks for your suggestions.

 

[jerryjerry05]

Start with a compression test.
Then check the points and condenser, rotor.
Vibration: prop, u-joints, the bearing on the PDS.
No gimbal bearing it uses a damper and drive shaft with a single bearing.

 

[madridbruce]

Start with a compression test.
Then check the points and condenser, rotor.
Vibration: prop, u-joints, the bearing on the PDS.
No gimbal bearing it uses a damper and drive shaft with a single bearing.

thanks for the information i will do all of the following and get back the results. can you replace the bearing without pulling the motor? my next is can the boat be made reliable for the ocean fishing i do? will the salt water destroy my exust manifold? the timing belt rubbs on the timing case they only last 30 hrs or so then start this whole miss timing thing and im dead in the water. thanks for your time. bruce

 

[jerryjerry05]

That motor is usually a very good/ reliable motor.
The bearing can be replaced with out removing the motor.
The salt will ruin everything eventually.
How old is the manifold?
They can last anywhere from 15-25 years.
The rubbing belt sounds like an alignment problem.
Compression test?

 

[madridbruce]

hey again . ok the al lingment is off because the belt tensioner is not working properly i assume? ya it has ran strong ive had the boat 2 yrs and done some tlc to it. the manifold looks newer than the heat exchanger. that looks to be original. i will do the compression test in the next couple days . stary with the 1 cylinder and what should a normal reading be? if the timing was off 5 to 10 degrees would that cause the boat not to start? (back from top dead center) thanks for your tme. brucem

 

[jerryjerry05]

5-10 off might stop it from starting?? Probably not.
Check for spark?
Compression should be all 4 about the same readings.
Different gauges read differently.

 

[madridbruce]

No Title

ok i did the compression test here are the readings (refer to the pics below). my questions - will the timing being off effect the readings? is the problem with these reading valves or pistions or both? and finally ,what are the normal readings?

 

[Alan Lloys]

All the readings are a bit low and #4 indicates that something is really amiss.
You should have in the 120 psi range or so on all cylinders.

The first thing I would do is to check that the timing belt has not skipped a tooth. You need to check that the cam and crankshaft is synchronized properly.
If the cam is off by a few teeth it will not start and you will get weird compression readings as the valve timing does not match with the piston movement.

 

[madridbruce]

ok thanks ya this sounds like i need to do the timming again. 10 deg on the ignition timming? what does that mean? if i turned the cam counter clock wise to reset the timing will that matter?

 

[jerryjerry05]

Resetting the timing isn't what you need to do.
The timing belt needs to be installed right and then the timing needs to be set.
The timing belt when installed wrong will open and close the valves at the wrong time.
Check that and if it's right??? Then I'd think about pulling the head and check for damage??