Volvo AQ170C Advice

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iwalm1979

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Hi

This is a genuine "for a friend' job - We've just changed our Princess 32 to a Birchwood TS31, but I've got a friend who has bought a Princess 25 [unfortunately a bit on my recommendation!!]

This has a Volvo AQ170C 6 cylinder engine - On the trial ran fine, but on having a standard service done noticed some emulsification in the oil - Head gasket replaced and water pump rebuilt in the process, so he was hoping all was well. However, compression test today indicates 140PSI-150PSI on cylinders 2,3,4,5,6 but cylinder 1 is showing 90PSI. Given the HG has been done, suspect it must be piston rings, but looking for advice there (we aren't mechanics) and beyond that how far do you go to patch this up or is it a run it until it breaks kind of affair. Carbs all checked and cleaned.

Many thanks!
 
My Dad has the exact same engine, with exact same symptoms and compression numbers. No matter what we did we always had a little emulsion in the oil and it occassionally backfired, other times it ran well. We decided to do more investigation and found some crackes in the valley, small insignificant cracks, but enough to give problems. After a lot of repair attempts we are putting in a replacement 4.3. My boat has the 4.3, which is basically the same engine and in the past had similar problems. In this case it was down to the wrong and insufficient sealant on the bead bolts, which go into the water jacket, or at least thats what we suspect. its in the workshop at the moment ghetting a full stripdown and rebuild - its been an expensive month!

I have watched all the usual youtube videos about the v6 engine an dits a dependable unit, but has some quirks. The main thing that kills them is frost damage and poor maintenance, and thats whats happened to both my and dads boats, both before we got them. The only good thing is both boats should be right by the end of the month.
 
diverd said:
My Dad has the exact same engine, with exact same symptoms and compression numbers. No matter what we did we always had a little emulsion in the oil and it occassionally backfired, other times it ran well. We decided to do more investigation and found some crackes in the valley, small insignificant cracks, but enough to give problems. After a lot of repair attempts we are putting in a replacement 4.3. My boat has the 4.3, which is basically the same engine and in the past had similar problems. In this case it was down to the wrong and insufficient sealant on the bead bolts, which go into the water jacket, or at least thats what we suspect. its in the workshop at the moment ghetting a full stripdown and rebuild - its been an expensive month!

I have watched all the usual youtube videos about the v6 engine an dits a dependable unit, but has some quirks. The main thing that kills them is frost damage and poor maintenance, and thats whats happened to both my and dads boats, both before we got them. The only good thing is both boats should be right by the end of the month.
Click to expand...
AQ170 is a straight 6
 
Thanks for the support on this so far - Think the plan is to get the head sent off to be skimmed (thats our engineers plan) so will see what they come back with when they get it on the bench and inspected.
 
Many yaers ago i helped a friend working on this engine . Great , smooth running engine . I personally would check if the spark plug on the cyl1 looks different to other cylinders and monitor overall oil consumption . If the engine runs good and oil consumption is acceptable just leave it alone since you look not only at new piston rings but also re-bore and hone the cylinder . Further : water in oil has nothing to do with worn piston rings , so monitot that also . How much water ? How does the engine run?
 
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