AD31P oil in coolant tank, won't rev above 3000.

While I do appreciate fuel cost concerns I'm great fan of allowing engines to be used to work as they were designed to now and then.

At every season start, after allowing them to warm up etc, checking everything visually, listening etc. , I'll bring it onto plane then let them pull WOT one at the time for a few minutes. If they perform as the previous year (each keeping the plane) it is an indication of things being in good order.

During the season I regularly let them work flat out for 15-30 minutes, then go 2-300 rpm back and continue for at least same period.

Of course any suspicions at any time are investigated and acted upon.
 
madabouttheboat said:
That is not an original engine for that boat so there are lots of potential things to look at if the conversion was done badly. What drive model and prop size is fitted? Do you know the drive ratio?
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Friend had the similar problems with low revs and found that boat had petrol engines originally and had been re-engined with 31s but staying on original drive., It worked ok but low top speed even after lots of diff props.
If you are staying inland or not wanting to plane should not present a problem until resale.
As Madabout said not a builder fit engine.
 
stelican said:
Friend had the similar problems with low revs and found that boat had petrol engines originally and had been re-engined with 31s but staying on original drive., It worked ok but low top speed even after lots of diff props.
If you are staying inland or not wanting to plane should not present a problem until resale.
As Madabout said not a builder fit engine.
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That’s exactly where I was going. Original drive and prop may be the problem. If it had a V8 for example, the drive ratio will be set up for max rpm in the region if 5000. That will need more than a prop change to overcome. AD31 Needs a 1.95:1 drive from memory.
 
madabouttheboat said:
That is not an original engine for that boat so there are lots of potential things to look at if the conversion was done badly. What drive model and prop size is fitted? Do you know the drive ratio?
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not sure about prop size or ratios but it fitted with a (presumably matching) Volvo duo-prop outdrive.
 
I think the boat & engine history deserves a bit of investigation as it seems the OP doesn't have all details.

Helidan said:
.. I do believe it's the original turbo from 2001.
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Since it is a sterndrive model (Aquamatic in Volvo terms) the model number must be AQAD31. This engine was made 1986-1989, so 2001 sounds wrong.

The instruction book pg 14 states drive gear ration to be 2,31:1 (1,95:1 for heavy duty). If the original engine was petrol is would have had a higher rpm range than the AQAD31's 3700-3900 rpm so the props hardly are correct.
 
ChromeDome said:
I think the boat & engine history deserves a bit of investigation as it seems the OP doesn't have all details.



Since it is a sterndrive model (Aquamatic in Volvo terms) the model number must be AQAD31. This engine was made 1986-1989, so 2001 sounds wrong.

The instruction book pg 14 states drive gear ration to be 2,31:1 (1,95:1 for heavy duty). If the original engine was petrol is would have had a higher rpm range than the AQAD31's 3700-3900 rpm so the props hardly are correct.
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I believe the diesel has replaced an original fit petrol utilizing the original sterndrive.
Cure the oil problem 1st
 
madabouttheboat said:
The AD31p, (150hp) if that’s what it is, was produced up to around 2004 I think.
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This is the engine I have, there are documents onboard dated 2001 when the unit was first installed. Hopefully I will have an engineers report tomorrow and will be able to provide an update. Really hoping the head doesn't have to come off.
 
Just to update the thread, engine has now had all sorts of pressure tests carried out and the engineer believes the turbo is responsible for some oil getting into the fresh water circuit. So where is the best place in the UK to get the turbo refurbed? We will also be sorting a leak in the power steering system and servicing the outdrive ready for start of boating season next year.
 
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