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Black Soot?

Justin Lee

Moderator
I have a 1985 E32-III with a Universal M25 Diesel & a feathering Maxprop. Last year I replaced the "riser" and all of the hoses exiting the manifold. This year I am noticing that when I put her in reverse...I notice black soot on the water after backing down? I have tried running it hard in reverse for several minutes but it doesn't seem to clear up...just more soot? There is no noticable smoke or anything...just soot on the water? Anybody have any ideas what might be causing this?:confused:
 

jwolfgra

Member II
I think the black soot is incompletely burned Diesel Fuel, analogous to the black smoke you see from old buses... A couple of possible sources are: 1. Engine is overloaded - check prop pitch ensure that it's correct, 2. Air filter is clogged causing engine to run rich - replace filter, 3. Fuel Injectors are worn out of adjustment - check your bank account. What are the hours on your engine? I'd suggest checking/replacing the airfilter first and see if it helps, that's quick, easy, and cheap.
 

Geoff Johnson

Fellow Ericson Owner
Except that Justin implies the problem is encountered only in reverse. I don't know the specs of the Hurth transmission, but if the reduction ratio is much different in reverse, it seems to me that reverse could be putting a greater load on the engine, hence the soot.
 

jwolfgra

Member II
I've got a Hurst Transmission on my boat and I know the ratio's are equivalent re forward to reverse. Can the pitch setting on the MAX prop be set to different pitches forward vs. reverse, if so, that could be the problem.
 

Geoff Johnson

Fellow Ericson Owner
I have a Maxprop like Justin and I know from playing with it that the pitch in forward and reverse is the same. I get soot on the transom (I believe my prop is overpitched because I achieve hull speed at about 2200 rpm), but I don't recall seeing it on the water. Of course, because the prop and shaft on the 32-3 is at a pretty steep angle, the hydrodynamic characteristics of the prop in reverse could be sufficiently different than forward to cause a different load on the engine.
 

Justin Lee

Moderator
...Yes, It ONLY happens in Reverse? I can run it at almost full throttle in the slip tied up in forward & NO black soot??? I too can reach hull speed at about 2200 rpm's with my Maxprop, I may try to reduce the pitch this winter. Unfortunately, I have to pull the boat out of the water this weekend due to low water conditions so I will have a LONG time to think about this! I will also contact the folks at Torresson, thanks for the suggestions.
 
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