D4-300 Max RPM

[Robvic]

Cruising in our new (31 hrs) R-31S last night we briefly ran at WOT ~3600RPM and 21+/- knots. This is above the rated 3500RPM per the Volvo specifications.
Is this safe and/ or does it compromise the engine and warranty? Is the R-31 under propped?
Thanks,
Rob

 

[dclagett]

I did not buy my boat new, however when the boat was originally delivered the RT dealer had a Volvo Penta dealer checked the performance of the engine and logged the data with Volvo Penta. This data included wot rpm. Did a VP dealer do that for your boat?

I was told by the local VP dealer that the boats are normally propped so one gets some additional rpm in the boats delivered configuration knowing that the owner will add stuff/weight which will lower the wot rpm. Also as you get some growth this will also lower the rpm.

If you need to adjust the wot rpm the way to do that is tune the prop.

 

[Red Raven]

It is normal for the WOT rpms to vary somewhat with wind and current. You probably had a bit of current pushing you causing the engine load to decrease and rpms to increase. Check it again when you are going against the current and you will likely see the opposite results. As long as the average over many of these tests is within 100 rpms or so it is likely propped correctly.

 

[BB marine]

As dclagett said your engine should have had a PDI performed at or before delivery. The WOT is recored in this form and sent to Volvo for warranty registration. 100rpm over spec max rpm is acceptable with a light load, 3630 is max power set governor. After you get the boat loaded 3530 to 3550 would be a good max RPM. We have a D3 with a rated max rpm of 4000rpm. When we took delivery the Max rpm was 4150 rpm with a lightly loaded boat and two onboard.I performed the PDI myself because the selling dealer was not equipped to do it. When I went over the completed form with a certified Volvo technician he said Volvo doesn't want to see any more then 4130 rpm. I left it alone with the thought that if we have more passengers and equipment it will load it down more. With the added equipment now ,RIB and motor on the transom 4 people on board the engine turns 4030 wot. I don't run there very often but I always run it up just to make sure the engine is loaded properly. 3350 to 3400 is my high cruise speed 85% of wot. I would rather see 100rpm over Max then 100 rpm under Max.