loss of speed RPM OK

[ianwoods]

I have a volvo 5.7OSI petrol engine with composite drive and duoprop. I believe the year of make is 2006, I bought the package new in 2007.

The problem I have is a lack of speed of late, usually I achieve 20- 21knts at 3200rpm, now I am getting 17-18 knts at same RPM. I can still achieve approx 4800rpm.

I'm told by Volvo tech it may be the cone clutch, may be the prop hub slipping maybe this maybe that.

I've done 260 hours, serviced all religiously and only had leg and engine service 2 weeks ago, all compressions, oils etc fine and I'm told compression etc was "as new" levels.

The prop is the plastic job, lots of people saying its that but it's only a year old and mint, I have not had this problem before.

Prop specialist says very unlikely for duoprop to have a slipping hub.

Before I part with a grand to start pulling my drive apart I'd appreciate any suggestions.

First post, I hope I'm in t he right place.

Thanks in advance !!

Ian

 

[Ciera2450]

Re: loss of speed RPM OK

have you added weight to the boat?

 

[Bondo]

Re: loss of speed RPM OK

I have a volvo 5.7OSI petrol engine with composite drive and duoprop. I believe the year of make is 2006, I bought the package new in 2007.

The problem I have is a lack of speed of late, usually I achieve 20- 21knts at 3200rpm, now I am getting 17-18 knts at same RPM. I can still achieve approx 4800rpm.

I'm told by Volvo tech it may be the cone clutch, may be the prop hub slipping maybe this maybe that.

I've done 260 hours, serviced all religiously and only had leg and engine service 2 weeks ago, all compressions, oils etc fine and I'm told compression etc was "as new" levels.

The prop is the plastic job, lots of people saying its that but it's only a year old and mint, I have not had this problem before.

Prop specialist says very unlikely for duoprop to have a slipping hub.

Before I part with a grand to start pulling my drive apart I'd appreciate any suggestions.

First post, I hope I'm in t he right place.

Thanks in advance !!

Ian

Ayuh,... If it's a moored boat, clean the hull...

 

[Don S]

Re: loss of speed RPM OK

Bent & dinged up prop blades will also do it.

 

[Maclin]

Re: loss of speed RPM OK

I would think props before I took the drive apart! And hull as mentioned, the drive would be my last thought.

Regarding the plastic props, do you mean Composite? or really plastic? I know the plastic ones advertised for the 290's and DP-A style drives were only for spares in a pinch and were not designed to go above 25mph or maybe less, they were for getting a boat back to the ramp then removed and shelved until the shop needed them again, that kind of thing. I am not all that knowledgeable about the later model ones like yours, so I am ready to learn something here.

 

[insttech1]

Re: loss of speed RPM OK

just out of curiosity, what are you using to measure speed? a gps, or boat's integral speedo?

 

[ianwoods]

Re: loss of speed RPM OK

Thanks for the replies guys. The boat is in New Zealand and stored in a drystack so the hull is as new, waterblasted and stacked after each use.
The Prop blades are plastic, I assume thats the same as composite ? and were new last season, not a mark on them however previous ones were lightly damaged which gives me some reason to doubt the hub condition however the "experts" in New Zealand tell me these hubs are unlikely to slip.
Maclin, I've heard they were only to be emergency props but I've had no issues over the past few years. Will consider going aluminium beofre pulling the leg apart.

I'm using GPS to measure speed in similar conditions. I get out two to three times a week to fish so know the boat fairly well.

Thanks to all so far..... look forward to more feedback based on my reply please.

Oops, ciera, no weight added either, probably less than usual, low gas, zero water in the tank and just me on board.

I'm seeing a lot on here about exhuast issues, I wonder if the tech who serviced the drive put the thrust washers etc in place correctly ? Need a dam prop tool to get it off myself and they're $300 at Volvo

 

[Maclin]

Re: loss of speed RPM OK

Composite is not the same as plastic. Per Maclin's Dictionary and Thesaurus....Composite usually means stronger and lighter than pure metal alternatives. Plastic means light duty and way weaker than any metal alternatives.

 

[ianwoods]

Re: loss of speed RPM OK

Thanks Maclin, they're the same as the original volvo "plastic" props so composite I would think. Incredibly hard black plastic.

Anyway, can anyone tell me whther the symptons would indicate slipping of the cone clutch, I know everyone says its unlikely and I'd have to agree given time of use and age of unit, servicing history etc but......wouldnt the cone clutch wear out VERY quickly if it were slippping, I did two hours at about 3200 - 3500 rpm a few weeks back, sure that torque going through a slipping clutch would tear it to shreds ? I'm amazed how the reports here also show how tough these prop hubs are to go on for quite some time when obviously slipping.