06 DF70-Low RPM issues.

[Brainburn]

Hello All,
I just joined the board and absolutely love it. A ton of information here. Did a search real quick and didnt find anything relevant to the issue at hand so if I missed it please forgive me.

Information:
-2006 DF70
-approx 50hrs
-has 20 hr service (absolutely anal about break in period)

Fuel tank vents are opened.

The problem:

I picked the boat up, MacGregor 26M, and started the break in period but never exceeded 5200 rpm-ever. 5200 was the max rpm I could get out of the engine at the time. Figured it was due to break in period and didnt want to push it.
Since then my fuel efficiency has gone to crap and I cant get anything over 4800 RPm with a good tail wind and both my wife and kid paddling 8)

I have adjusted the throttle linkage (almost to the end of the threaded portion) and the only result was to increase the idle to the point it would SLAM into reverse. I have since backed it down to it's original length.

My next step is to check the fuel system specifically the filters to check my flow.

I checked the specs and it has an operating range of 5200-5800 rpm. I am no where near it now.

Any and all help would be appreciated.

Thanks all,
Mike

 

[JB]

Re: 06 DF70-Low RPM issues.

Howdy, Brainburn.

Welcome to iboats.

You need a Service Manual.

Though 5400 is in the 5200-5800 operating range it is still low.

I suspect that you are over propped. That will lug the engine and make it burn too much fuel.

Repost your description above in the Prop Forum for advice on how to optimize your DF-70 performance with a better prop pitch. Tell them what I told you here.

I am not familiar with the MacGregor 26M. I had a DF-70 on a Boston Whaler 17' and just loved it. I used an 18" pitch SS prop to reach 5800 rpm at WOT.

Good luck.

 

[Brainburn]

Re: 06 DF70-Low RPM issues.

Thank you sir.
I will do as requested.

As a confirmation of current RPM I am running an average of 4800 with the once high of 5200.

Just out of curiosity, why would it drop from 5200 to 4800? I thought I may have stretched the throttle cable but it was not so.

Thank you again,
Mike

 

[JB]

Re: 06 DF70-Low RPM issues.

If you are in fact overpropped any small change in the load or balance can cause worse lugging, further lowering your WOT rpm.

On my Boston Whaler that would peak at 5800 rpm with the 18" prop, I put a 50lb front troller motor on it. . . no other change. . .and my WOT rpm dropped to 5200. I switched to a 17" prop and was back at 5800.

That engine is very sensitive to load and balance, sort of like climbing hills in overdrive.

 

[Brainburn]

**UPDATE**-06 DF70-Low RPM issues.

**UPDATE**-06 DF70-Low RPM issues.

Been talking to some folks at a local (big) Prop shop.

I am currently running a 3X13.75X13 which is 2 under the pitch they recommend.

I am getting the feeling that it may not be the prop.
For the sake of argument. What would your next step be to figuring out the issue? I am on the way outside to pull the filters and check them.

I will let you know the results of that.

Mike

 

[Brainburn]

Re: 06 DF70-Low RPM issues.

Fuel Delivery system is clean and un-obstructed. Both filters.

 

[Brainburn]

Re: 06 DF70-Low RPM issues.

Fuel Delivery system is clean and un-obstructed. Both filters.

Is there a way to edit the posts so I dont keep adding additional posts to scrub through?

 

[JB]

Re: 06 DF70-Low RPM issues.

The next step for me would be at the dealer.

Each new bit of info points a new finger. This time it sounds like loss of torque. That could be valve adjustment, ECU, high pressure fuel pump or an injector problem, just for starters.

I would require a dyno test to prove whether or not it is making full advertised power (torque is the important factor). My guess at this point is not.

 

[Brainburn]

Re: 06 DF70-Low RPM issues.

The next step for me would be at the dealer.

Each new bit of info points a new finger. This time it sounds like loss of torque. That could be valve adjustment, ECU, high pressure fuel pump or an injector problem, just for starters.

I would require a dyno test to prove whether or not it is making full advertised power (torque is the important factor). My guess at this point is not.

Please dont say that.
Is there anything..anything else that could be done on my end?

Please, please, please, please....

 

[JB]

Re: 06 DF70-Low RPM issues.

This is a 2006 engine. It must be in warranty.

Why do you not want them to honor it?

 

[Brainburn]

Re: 06 DF70-Low RPM issues.

This is a 2006 engine. It must be in warranty.

Why do you not want them to honor it?

Well..
I have heard nothing but horror stories concerning the support.

I have to trailer it through Seattle traffic to get back to the dealer.

it is prime season so I am sure it will take longer

Seattle traffic.

Seriously, It is just a major hassle and I am dreading it.
I will contact them tomorrow when they open and figure out what to so.

Another serious note. Thank you for the assistance.