7 kts max @2,900rpm; 2006 21EC with yanmar 30; normal?

[greenghost45]

I have a deal pending on a 2006 R21EC with the Yanmar 30 hp. I was not able to attend the sea trial but i did have a mechanic aboard. The WOT speed as confirmed on the plotter was 7 kts (sog) @ 2,900. rpm. Does this sound unusual for an R21EC? I think that the rpms should be a bit higher, thus perhaps the boat is overpropped. The prop is a 4 bladed bronze; I don't know the diameter or pitch. The mechanic felt the engine was running well and it only has 370 hours. I'm not worried that the speed is too slow for me (former sailor), just want to be sure that the boat is performing normally. Thanks for any advice or experience from other R21EC owners.

 

[captstu]

You don’t say which Janmar engine you are testing. A previous boat with a Jan more 3HM 30 F had a wide-open throttle rpm rating of 4000. I raised the alternator rating above the nameplate rating, foolishly, and dropped wide-open throttle rpm the 3200. Eventually this overheated the engine and cracked a piston. Mack boring explain to me that the governor in the engine was trying to raise the RPM to 4000 by adding extra fuel. The unburnt fuel was pushed down into the oil, diluting the oil and causing the damage.

If your engine is rated at 4000 RPM wide-open throttle you are seeing this problem. I don’t know the rating of engine but I suggest you look up the rating. It comes into numbers, the one hour maximum and the continuous maximum.

I believe if your engine will not reach 80% or so of continuous rating something is wrong.

The engine may be over propped, the prop may be dirty, the bottom may be dirty, or something more serious. You might consider testing the oil to see if it is the diluted with Diesel fuel.


Any diesel fuel dilution should be considered serious.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[dalee62]

I run my 3YM30 at 2700 which gives me 6.5 KTS.

Dave

 

[greenghost45]

I run my 3YM30 at 2700 which gives me 6.5 KTS.

Dave

This one is also a 3YM30. So 7kts @2900 sounds about right, compared to your boat. Thanks for the reply!

 

[greenghost45]

I run my 3YM30 at 2700 which gives me 6.5 KTS.

Dave

This one is also a 3YM30. So 7kts @2900 sounds about right, compared to your boat. Thanks for the reply!

Thanks for the reply and info on your R21EC. While you get 6.5 kts at 2,700 rpm, just out of curiousity, what is the max speed and RPM of your Ranger with wide open throttle (WOT). Thanks!

 

[greenghost45]

We finally did get her on the water last week. It was a calm day and with 5 aboard, WOT delivered about 8.4 Kts at about 3,600 RPM. Just about bang on based on the experience of other people kind enough to reply and share their experience. And the Heatcraft heater was brilliant. Kept the cabin toasty warm on a day cloudy day with an air temperature of about 1C. Guessing that the water temperature was around 8C. Thanks to everyone who replied! 😀

 

[Two killicks]

Your specs sounds good for doing 7 kts at 2900 rpm. Your WOT max rpm should be in the 36-3800 rpm range.

Mine goes to 3750 rpm at WOT for a 8,5 kts with a lot of stuff onboard.

we cruise at 2200 rpm for a 5.5 kts most of the time and WOT for 5 minutes every hours as recommended by Yanmar.

 

[greenghost45]

Thanks for the reply. I may have been a little low on the RPMs for WOT as I was relying on memory a week or 2 later, but it was somewhere north of 3,500. And I seem to recall a "sweet spot" at at about the same place you mentioned of 2,200 rpm. I have her more or less laid up for winter (yes, even on Vancouver Island, we are experiencing winter this year), but plan to be back on the water in February or March!

 

[Two killicks]

February or March, that is nice out there! we usually put the boat the last week of may and retrieve in late September. time to move out West...