O-34 Black exhaust:Prop pitch, or what

J

JamesBlakeJones

Member II
Listmates, I have a 1989 Olson 34 with a Universal M25XP 23 h.p. diesel engine. It has been quite reliable. For better or worse, the only service I've done is changing the oil twice a year, changing the zinc in the ?heat exchanger, and changing the fuel filter. Now, the engine puts out black exhaust water at times, particularly when revved up, under load. Sometimes it streams black liquid right after you throttle down. A couple of years ago, I put on a Max Prop propeller. They set the pitch to match the Gori that was on there before. Is this black liquid from the exhaust a serious symptom? Do I need to change the prop pitch? Could it be a dirty air filter? (The wire mesh interior air filter is coated in oil and needs to be cleaned). Are there other possibilities? How do you get the prop pitch correct? My tachometer is erratic and I don't trust it, so I'm not sure at what rpm the symptoms are occuring.

Thanks in advance,

James Jones
Olson 34 "Sunwood"
Seattle
 
G

Geoff Johnson

Fellow Ericson Owner
I have a Maxprop on my 32-3 (M25 Universal) and had it repitched this year to get the cruising RPM up to about 2400. There has been a noticeable decrease in soot on the transom. Also, because I upgraded my alternator to a high output model, which throws off the tachometer reading, I installed the $65 Tinytach http://www.tinytach.com/tinytach.html, which reads the rmp's from the pulses in the high pressure injector lines by means of a bolt-on sensor. BTW, if you change the pitch, the Maxprop web site lists somewhere the relationship between pitch and rpm's. I believe this is the statement: " A two degree change in blade angle will change the engine RPM by 13-15%, at the same boat speed."

However, I have never seen "soot" in the cooling water. Have you checked to see if you are losing oil?

PS, on further reflection I do recall having seen black soot deposited on the water after initial startup. I assume it had collected the the exhaust system. Now I see only a bit of rust coming, I assume, from the mixing elbow after the boat has remained idle for a week.
 
Last edited:
Loren Beach

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
just a "tiny" little question...

http://www.tinytach.com/diesel.html

Geoff, Is this the unit you installed?

Can you describe how the power needs are handled? If direct to your house bank, is it fused? How often do you replace its internal battery?

I like the idea of a reliable tach if and when we add a higher-output alternator. (After this year's vacation, the Admiral is moving the refrig. idea up the project list...)
must... have... more.... AmpHours!.............
:)

Thanks,

Loren
(M25 XP Universal)
 
G

Geoff Johnson

Fellow Ericson Owner
Yes, that's the unit. I installed a small positive bus bar just over the engine which is engergized when the ingnition is on. To this I attached the TinyTach, the alternator field wire and the fuel pump positive leads. So, in effect, I am relying on the fuses already in the circuit. This way the TinyTach also works as an engine hour meter, although come to think of it, it is probably smart enough not to start counting until is senses pulses in the fuel line. It is a sealed unit, so the internal battery is not replaceable. I recall, however, the literature stating that it is a lithium battery expected to last at least five years. I am sure the unit will work with a dead internal battery, but won't keep track of engine hours.

After adding a Balmar, I found that my old tach was still reliable, in the sense that it there is a linear relationship between apparent rpm's and actual (I actually measured four data points with the TinyTach, ploted them against the the Universal tachometer readings and satisfied myself there is an an exact linear relationship). So my TinyTach is hidden in the engine compartment and I continue to rely on the engine panel tach, knowing that 3000 rpm's is acually 2350, etc.
 
Last edited:
E

escapade

Inactive Member
James;
I have a M25XP Universal in my E34, also. Fixed the tach by cleaning the terminal's on the back of the tach w/Scotch Brite & moving the adjustment screw on the back of the tach back & forth a couple of times (carefully note the realitive position of the adjuster and return to the same spot & put the wire's back in the same locations!!!) This fixed my tach. It's a fairly simple set-up, but all low voltage electrical circuts are VERY dependent on good connections. Increased the pitch on my prop by 3" this year which resulted in a increase in soot for the first 8 hours or so of engine operation. After that soot has become almost non existent. I am blending 10% soy bean diesel w/regular fuel which will have a tendency to clean the injectors and make starting easier. You should be seeing 6.5 to 7.0 kn @ 2200 RPM with your engine & w/l length. 2200 to 2400 RPM is a good cruising range for this engine, just find the spot where the vibrations are at an acceptable level in this RPM range. If the soot continue's that is an indication that you have too much pitch in the prop, which will also show up as a noticable increase in fuel consumption. Should be using .8 to 1.0 gal per hour @ cruising speed. If you try to push beyond "hull speed" (7.25 kn. aprox.) your fuel consumption will skyrocket, soot will increase, and you will shorten the life of your engine. Hull speed is 1.34 times the square root of the water line length. Have fun & sail fast. Bud E34 "Escapade"
 
J

JamesBlakeJones

Member II
Listmates, Thanks for all your replies...Perhaps I'll have the prop pitch adjusted when I haul out this winter. I have a considerable increase in fuel consumption, though it seems to have gone from 1/3 to 1/2 gal/hr to 3/4 gal/hr. I am only able to push the boat to about 6 knots with this and previous prop. The MaxProp I have is a two blade, if that makes any difference. The idea about the add-on tach is a good one, though I think I'll first try cleaning up the connections on the original one. Thanks again,
James Jones
Olson 34
"Sunwood"
Seattle
 
G

Geoff Johnson

Fellow Ericson Owner
Don't put too much stock in the OEM tach. Tachs that run off the alternator (as opposed to mechanically reading a mark on the flywheel) are nortriously unreliable (even with clean connections). For example, using a manual tach (which I got on eBay before I discovered the Tinytach) I found that my Universal tachometer read a consistent 200 rpms low.
 
You must log in or register to reply here.
Top