Volvo penta ad31 power

[CBC]

Hi all. Seeking some advice please…. I have recently bought a Hardy Seawings 254 with a diesel Volvo penta AD31 coupled to a 290 out drive with new A7 duoprops. But it’s struggling to achieve 8 knots!! Engine revs are around 2200 rpm max. When I’m neutral she will rev up to 3200 rpm.
I don’t think A7’s should be over propped for her, or maybe I’m wrong?
anybody else experienced a similar issue, I’m not sure whether to buy new props (say A5’s?) or if the issue is the engine?
Any advice would be really appreciated. Or are there any good recommendations for marine mechanics in the south east (Kent) who could take a look

 

[tico]

Turbo siezed?

 

[Momac]

I had Sealine s23 with a kad32 and 29 dp-e outdrive and it had A4 duoprops
So I would say yours is well over propped . But that's just my best guess.
What really need is input from another owner , or perhaps from the previous owner of your boat.

 

[oldgit]

Before getting all complicated and expensive ...............stuff that costs nothing first...................Do you have a dirty bottom ?
When was it last out of the water ?
Fouling very bad this year in this area. Medway and Swale.
Sometimes 3/4 months has been enough to produce considerable amounts of weed/slime and barnacules.
Boat normally able to do 20 + knots plus reduced to 12 knots.
If possible get out on the swim platform run your hand along the hidden bottom of the boat near the trim tabs , it might reveal a good coating of muck.
It might............. just be case of lift and jetwash !

 

[CBC]

Before getting all complicated and expensive ...............stuff that costs nothing first...................Do you have a dirty bottom ?
When was it last out of the water ?
Fouling very bad this year in this area. Medway and Swale.
Sometimes 3/4 months has been enough to produce considerable amounts of weed/slime and barnacules.
Boat normally able to do 20 + knots plus reduced to 12 knots.
If possible get out on the swim platform run your hand along the hidden bottom of the boat near the trim tabs , it might reveal a good coating of muck.
It might............. just be case of lift and jetwash !

Good advice, thank you, but I forgot to mention it was antifouled a month ago with fresh paint.

 

[James jameson]

Engine should rev to nearer 4100 off load
as tico says about is the turbo free ?

 

[CBC]

Thank you. Looks like I need to check the turbo! If it was turbo problems wouldn’t I notice smoke though?

 

[dankilb]

Thank you. Looks like I need to check the turbo! If it was turbo problems wouldn’t I notice smoke though?

Not if it’s seized/stuck or otherwise not spinning up and making boost. The smoke tends to come from oil passing the seals/bearings, which it won’t do if it’s inop.

 

[James jameson]

I Should like to see the off load revs up to where they should be

Worst case being the previous owner stuck a wrong ratio drive on it

 

[CBC]

Not if it’s seized/stuck or otherwise not spinning up and making boost. The smoke tends to come from oil passing the seals/bearings, which it won’t do if it’s inop.

Thank you, really helpful

 

[scottie]

Where is the boat used
And try to find out what original performance was
Depending on either answers you may find that at some time a decision was made to deliberately over prop to keep the revs down

 

[CBC]

Where is the boat used
And try to find out what original performance was
Depending on either answers you may find that at some time a decision was made to deliberately over prop to keep the revs down

Hi Scottie. Thanks for taking time to help.
She was on the Thames and prior to that somewhere in Scotland. A couple of months ago when I bought her I re-propped it before I put it in the water due to slight prop damage through grounding from previous owners, but I just replaced ‘like for like’ with what was on it with new ones (A7’s) but now I’m wondering if she was incorrectly propped before I bought it.
do you think that wrong props would be enough to cause such a difference in speed? …8 knots compared to a potential 18/20 knots?
I’m using her on coastal waters and rivers. Craig

 

[stelican]

Thank you. Looks like I need to check the turbo! If it was turbo problems wouldn’t I notice smoke though?

Had similar problem.
Turbo not spinning due to lack of use age.
No smoke but black trail of partially burnt fuel left in wake.
Same revs as you.
Freed of stuck turbo back to full revs.

 

[Scubadoo]

I have a similar size boat with a AD31 and based on what you have said I think you may have several issues. Mine came out of the factory with A6 props and I think your A7 props don't seem right to me, don't compare KAD32 as they were generally fitted with A4. So, if it were me I would fit A6 to start with, but I don't think your problem ends there...My AD31 at the start of the season will reach 4100rpm, so I think you have another issue there, not sure what though (Fuel related?). The turbo should cut in around the figure you quoted 2200rpm, so it suggests a Turbo problem, it is very easy to check, take the air filter cover off and check if you can spin the blades, just don't force it with a screw driver, it should spin freely. I had my turbo refurbished this year due to corrosion at the exhaust outlet, if the turbo hasn't been touched in 15-20years then it may spin freely but losing power due to corrosion which was my problem.

 

[scottie]

The Thames use is subject to speed limits I believe but don’t know which would support my suggestion of deliberately over propping

 

[QBhoy]

Hi. If the drive and engine is original to the boat…without any doubt at all…you have most certainly got the wrong props on there. Way over pitched for the usual set up and gear ratio installed. You’ll be wanting A4’s as a sensible starting point, if there is no other data available on what she should have. Michigan marine do a pretty good after market set for a reasonable price. You won’t find a new set from VP anymore. They changed to j series and some thing else I’m sure. 99% sure this is the issue.

 

[Ferris]

There is a Hardy owners club, maybe ask there? bound to be some owners with the same boat-engine combo.
Hardy Motor Boat Owners Club Home Page (hardy-owner.org.uk)

 

[volvopaul]

Hi all. Seeking some advice please…. I have recently bought a Hardy Seawings 254 with a diesel Volvo penta AD31 coupled to a 290 out drive with new A7 duoprops. But it’s struggling to achieve 8 knots!! Engine revs are around 2200 rpm max. When I’m neutral she will rev up to 3200 rpm.
I don’t think A7’s should be over propped for her, or maybe I’m wrong?
anybody else experienced a similar issue, I’m not sure whether to buy new props (say A5’s?) or if the issue is the engine?
Any advice would be really appreciated. Or are there any good recommendations for marine mechanics in the south east (Kent) who could take a look

Seized turbo

 

[QBhoy]

Seized turbo

Could be…but I doubt the turbo is even able to get going, with those props ?

 

[sogood]

I have the same ptoblem, with A6 props. These were on the boat when I bought it. I tried A3's with no change except that the revs got slightly above the 2000 RPM I had been maxing out at. Everything has been refurbished, cleaned or replaced with no change. I feel your pain.