Recommened cruising speed/RPM's for 2001 2520DV Diesel

[FishorSurf]

We are new owners and have a question about the recommended cruising speed on our 2520 DV, our first diesel:

Engine: Vovlo Penta Diesel AD41/DP (Duo Prop)

The previous owner ran 60+ miles offshore and ran it at 17 kt/3100 rpm when cruising. He also said he never used the trim tabs. When sea trialing it we noticed it took a very long time to come up on plane, and then only in the flat water when we came back in the harbor.

Last week we tried it at 17 kt/3100 rpm on the way out. We used the trim tabs to get up on plane and it ran fine until you hit a swell and went off plane. When it went off plane the speed dropped down slowly to about 12 kt. even though the throttle was in the same position.

Bottom line is we had to run at 20-21 kt/3500-3600 rpm to stay up on plane. This boat is much heavier than anything we have owned before. Not sure if we should be running it at that high of an RPM.

Any recommendations for how to run it and why would be greatly appreicated.

Thanks!

 

[BradV]

Not really sure exactly how much the hydrodynamics differ between a diesel and outboards but my boat doesnt even think about planing until at least 23mph. what is the max rpms of the motor? most outboards cruise at 2/3 max rpms or a little more. assuming that diesel isnt a big lugger you might be ok.

 

[Megabyte]

You might want to check with Volvo or Parker Marine to see what the optimum cruise and WOT rpm's are for that particular motor before worrying too much about her.

I have upgraded 9x24 trim tabs on my (outboard powered) 2520 MVSC and once I jump on plane, I can back her down to 8 to 10 kts and still remain on plane in sloppy seas. That would be using tabs, motor trim, and throttle together to achieve that goal.

We have a lot of current in the Bay, especially at the mouths of the tributaries, and it is not unusual for the boat to 'loose' 5 kts or more without the throttle ever being touched. It is just one of those things...

Every boat is different, and your 'sweet spot' will certainly be different than mine. It might just mean finding that combination (over time) that suits your vessel. :wink:

Good luck, and have fun exploring your new boat!

 

[BradV]

whatd you find out?

 

[FishorSurf]

We went out again on Sunday and got a better feel for how she runs. On the way out we tried the 3100 RPM/17 kt recommendation from the previous owner and it did ok but did not stay up on plane consistently.

On the way back in with fairly flat sea's we ran it about 3400 RPM/20 to 21 kts. and were able to keep it on plane consistently with trim tabs down and the outdrive trimmed to -1 or -2 on the drive position gauge.

We received excellent feedback on this issue on boatdiesel.com along with a list of things to check and/or try. I would guess you diesel owners out there already know about this site but if not, definitely check it out.

I guess the bottom line for me is I want the boat to run well and at the same time not put overdue strain on the engine. After having to rebuild the gas engine on our old boat last year I would like this one to last forever. :wink:

We went out over 45 miles and probably covered close to 200 miles by the time we got back in. It's a great feeling to have a quality boat that you know will get you out and back.

Thanks,

Jeff

 

[BradV]

whats your fuel burn? and your wot?

 

[Megabyte]

I'm wondering if you are propped correctly.
Did anyone on boatdiesel.com address that item?

 

[FishorSurf]

At this time we have not figured out the fuel burn or the RPM at WOT. Probably won't get a chance until next weekend.

The prop issue was addressed on boatdiesel.com so we will be taking a look at that too.

Thanks,

Jeff

 

[dcunniff]

17 knots from what I've seen is on the edge of planing, whether gas or diesel.

Diesel moving through bigger waves should lose less speed than a gas model. Gas or diesel on plane hitting smaller waves should go through them the same.

Dana

 

[checker22]

I have the volvo in the 2520. She does great on a plane and can normally get her up by 14-16 konts no problem. She'll stay up on plane as you back down to around 12 or so. Tabs and all as mentioned above play a huge factor. Start out with it all down. i'm running wiht A4 props adn just came from the A5s. i like the 4s better, well it worked out well for the season.. I'm toping our at like 3500 rpm at around 24-26knts.