props?

[fireescape]

hey guys ....could use some help. my boat seems to be running really rich. The transom and swim step are black after any long run. I changed the air cleaner to the new plastic style and replaced the oil breather. I'm running A4's and only able to reach 3650 rpm with a light load.Butch at oceanside marine center recommended A3's is the place to start. I am thinking injectors? Have you guys tried A3's? Seems like the boat will over-rev.... thanks for the help.... oh by the way I have a AD41b W/290dp

[Knot Now]

There has been a lot posted on props. I run A-3s but I have a 41P/DP290 w/1:2.78 gears I think you have 1:2.95 gears. I do have to watch the revs when I am running light. I could use an additional 200 RPM when I am fully loaded :rolleyes:

I run 3000-3200 rpm when I am cruisin and 3400 if I am in a hurry.

[DOGHOUSE26]

If the A3s don't get it done then it could be time for a turbo rebuild. Black smoke is a good indicator. Injector problems show as rough running over various RPMs , usually 1500-2500. Try props then fuel filters, if I pulled the injectors and there was any question I'd pull the turbo as well. Pull your air cleaner off and physically check how smooth your turbo spins; also check the side to side play. Inconsistant spinning or excessive play will help you decide the condition of the turbo.

[fireescape]

hey guys...thanks for the info... When i replaced the air cleaner I did a visual on the turbo impeller and it spun very free with no damage to the blades. I did not check the lateral movement, but i will. At 3400 what kind of speed are you getting? Am i thinking correctly that when i am fully loaded the motor should not work as hard with A3's? Less lug on the motor? If you guys are running A3's with A bigger motor, that sounds like thats were i should be!

I changed my fuel filters not to long ago, but it sounds like i better try that also. Does that cause the motor to smoke? Seems like I'm getting to much fuel? Thanks guys zack

[NoSlack]

It's more likely that you're not burning the fuel efficiently, than you're getting to much fuel. A set of new injector tips won't hurt and it's a job you should be able to do yourself for $200. See a post from 2005 on injectors. http://www.bocaboard.com/forum/showthread.php?t=531&highlight=injector

Lack of air is another cause for black smoke, but it sounds like your turbo spins free and you've changed the filter.

That brings you back to engine load. If you never could hit 3900 RPM with a moderate load in the boat, then I would say you're over propped and a set of A3's would be a good place to start. Try and borrow a set before you drop $600 on a guess and check idea.

The next this you can try is a magnetic fuel conditioner. I always thought they were a scam and wouldn't pay $200 for one. Last year I made one for $10 and think it really helps with filter life and smoke.
Read about them at http://kjmagnetics.com/proddetail.asp?prod=FuelMag1

Mike

[Knot Now]

My higher gears 1:2.78 make about 200 RPM difference in the prop shaft RPM at speed. At 3400 with just a little chop I am going 21-22 Knots.

[DOGHOUSE26]

Phil your ratio is 1.78:1 and you run A3s, mine is the more common in Blackmans 1.95:1 and I run A4s; 3400 RPMs on mine fully loaded is about 18-20kts. For some reason they say the 1.78:1 unit is stronger than the 1.95. The turbo blades don't usually get damaged; the bearing is the first to go south from lubrication problems and wear. My buddy with twin TAMD-41s has that magnetic conditioner and he swears by it! It really cleaned up his fuel tank and now when he gets to the second half of the tank he's not changing fuel filters every 3 running hours! You might also check your aftercooler and make sure the element is not clogged with oil.