View Full Version : AD41P with Duoprop drives

05-26-2009, 07:30 PM
"Problem: Excessive diesel fuel consumption.

I have two AD41's, each 200 crankshaft horsepower, side by side in a 28 ft Maxweld. The starboard engine consistently consumes about 30 percent more fuel, from a separate fuel tank, than the port engine. Both engines are operated at the same RPM's.

Question: What should I look for to correct the greater diesel consumption? Thank you for your suggestions.

05-26-2009, 08:28 PM
"How do You know?
The only way to be sure is to use separate tanks for each engine, and be SURE that the return goes to the respective tank as well and is not routed to both!
With that difference there should be a quite noticeable difference in performance/output."

05-27-2009, 09:22 AM
"Good point Morten. Thank you. Each engine has it's own, separate,and unconnected fuel tank. However, I have not confirmed the routing of the return fuel lines. I will investigate the return lines.

Both engines perform very well. Performance is not the problem. Thank you, again, for your interest and reply.

05-28-2009, 12:08 PM
Any other suggestion out there?

I have confirmed that the return fuel lines connection only to their respective fuel tanks. Eacn engine is independent from the other. There is no connection between fuel tanks.

What should I look for?

06-21-2009, 06:42 PM
"If the air filters and such are all new and/or clean, a cheap option would be to pull the injectors and have them tested by a shop. They usually test them for free. Another would be to switch injector pumps. If the problem follows the pump, have it checked out."

06-21-2009, 11:16 PM
Thank you very much for the sugestion. I'll follow-up on that this September when I removed the boat from the water, or sooner. We likely have someone in town that can check the injectors to specifications. At this moment I do not know where, but I'll get it done. Same on the injector pump. Again, thank you for your help. It's a big assist.


07-02-2009, 04:20 PM
"Hi there Bud,
A thought crossed my mind while reading your problem. The injectors & pump should be matched. go by the numbers on the pump ID plate & injector numbers stamped on them. When you get the injectors tested, check if they have 4 or 5 hole nozzles. You could find they have been serviced before & incorrect nozzles fitted. Failing that, overhaul pump or get it tested against spec. Hope this helps."

07-03-2009, 05:26 PM
I'll do it ! During late August or September, I'll have the boat out of the water for winter. That will be the time to follow-up on your suggestion.
One question:
Does the pump dictate the companion type of injectors, 4 or 5 hole?

I had the RPM gauges checked against the flywheel RPMs (at 3000 RPM underway) and apparently the gauge on the control panel is under-reading about 100 to 150 RPMs of the actual engine RPMs. That may account for a portion of greater fuel consumption. The comparison, I believe, was not electronically scientific but double checked with about the same results. So far, so good. I use the boat several days every week during summer. Thanks for your help.
pv (Alaska)"

07-03-2009, 08:39 PM
"Bud, In answer to your question - Yes & no. The 41 series engines come out in many different HP ratings. Often the main differences are pump, injectors & internal bits. Just important to know they are a matched set. Some nozzles are 4 hole, others are 5 hole dependant on HP & injector.Do you know or can you see numbers on both engines to do a quick comparison? Food for thought."

07-04-2009, 02:17 AM
"HI Bud,
It may pay to check gbox ratios, prop sizes and condition. Could be?

Cheers, Tassie.."

07-04-2009, 12:18 PM
"Thank you Tassie. I've done that. The out-drives were new from Volvo, a matched pair, only one serial digit number different, as I recall. The props are matched "A8's" aluminum.

Thanks for your help. I believe Dean's thoughts will put me on the right track. I've discussed with the local Volvo Penta authorized agency, had a rep in the boat while under-way, and they/he did not mention either the injector nozzles or the pump. Interesting.
I understand Coastal Marine in Seattle is very astute with Volvo, but they are 800 airline miles south of us.
Bud (Alaska)"

07-05-2009, 10:41 PM
Any injector pump shop that handles Bosch should be able to calabrate your pump and nozzles. It is a very similar pump to the Cummins pump in Dodge Trucks.

07-15-2009, 01:44 PM
"Excessive Fuel Consumption . . .
Following up on various suggestions, including Dean's, I have noticed this:

The air filter housing on my engine that uses excessive fuel is much smaller, about 6 inches in diameter (filter cartridge part No. 3582358) than my other engine. The more economical engine uses a cartridge that is about 8 inches in diameter and 3.5 inches wide. It's available commercially as well as from Volvo and obviously has much greater filtering capacity. (It's Volvo cartridge part No. 858488.)

I temporarily removed the smaller air filter cartridge from the "offending" engine, started the engine and noticed there was less smoke on start-up. I am wondering if the larger (older)air filter and cartridge enable more combustion air into the engine, more margin allowance for dirt accumulation during use and improved fuel efficiency?

Any experience of thoughts about this?"

07-15-2009, 05:14 PM
"Hi Bud,
If everything else checks out, you are probably on the right track given the size difference between the two air filter elements. Try it for a lttle while without a filter on the offending motor to compare consumption. There can't be that much crap in the air up there in Alaska!!! Failing that, remote mount a Pod style filter.
Good luck!