Volvo Penta D4 /altitude/RPM

[desertug]

I am having trouble getting beyond 1920 RPMS on D4 at 6k feet. Has anybody that has been to Lake Powell experienced any trouble "spooling " up at altitude? I bought a 19x18 prop and that worked last fall but now in the heat of a summer afternoon 86 degrees WOT yields 2psi boost and 1920 max RPM. Is there a way to disconnect from the transmission at the motor control and see if it is a engine program issue? Will repitching the prop to 19x18 or 17 get me in the ballpark of 2900 or 3000 rpms? I have no problem changing props for high altitude and sea level. The stock prop worked great in LA when I bought the R31S. 🙁

 

[Irish Mist]

I had this same issue on my diesel truck this year and it was a broken clamp on the turbo hose.. under load air was escaping defeating the boost to the turbo. In the truck I could hear the noise like air coming from a deflating ballon when I pushed on the gas.. Perhaps it is a similar issue.
Was an easy inexpensive fix.
Good luck

 

[Andrew Custis]

Hello,

I believe this is actually outlined in the owners manual for the Volvo Penta about elevation. I do know of a couple D4 users that run at altitude but the prop has to be significantly reduced to allow the turbo to spool up. If there is a way to get it back down to sea level to run it again to verify no other issues exist, this to me would be the first step.

Thank you,

 

[desertug]

Andrew do you know which prop they are using? I have already gone from the 19X21 that came on the R31S to a 19X19 perhaps I should go to 19X17 to totally fix the problem. I am going to go over the turbo plumbing as you suggest. Perhaps I should come back to sea level but I think it will be perfect because on delivery 26 hours ago it was perfect.

 

[SGIDAVE]

Andrew do you know which prop they are using? I have already gone from the 19X21 that came on the R31S to a 19X19 perhaps I should go to 19X17 to totally fix the problem. I am going to go over the turbo plumbing as you suggest. Perhaps I should come back to sea level but I think it will be perfect because on delivery 26 hours ago it was perfect.

If your tug has an Acme propeller, then I suggest you call Acme directly as their tech help is very good. Click here for their website and contact info. They will need your engine and transmission info and have basic rules such as "x inch pitch reduction = x increase in WOT." I'm confident that a further 2" pitch reduction WILL NOT gain 800-1000 rpm you are looking for. That will require several inches LESS pitch and probably less DIAMETER also.

 

[desertug]

Acme Propellers says not a propeller issue. Bad winterizing my fault/fuel issue going to change filters then go back to sea level if that dosen't fix problem

 

[knotflying]

Acme Propellers says not a propeller issue. Bad winterizing my fault/fuel issue going to change filters then go back to sea level if that dosen't fix problem

I really can't see how Acme can diagnose the problem over the phone. Yes, a blocked filter could cause an RPM issue, but to flatly state that it is not a prop issue and zero in on fuel seems like shooting from the hip. I would consult with Volvo and see what they say about operation at your altitude before I would start "fixing" things. And by the way, how long will you be on Lake Powell? If this is a temporary situation, why not just live with the poorer performance?