Yanmar 1GM - exhaust mark

[matt_york]

I have a Hunter Ranger 245 which has a straight transom.

When motoring, there is a build up of water that laps up the transom as the boat "squats" in the water. The engine outlet is in the transom and the exhaust water/ fumes wash all over the transom leaving a pronounced and stubborn black exhaust mark. I think this is exascerbating the rusting of the rudder fittings and in any event is very hard to remove.

Someone I spoke to at the boat show suggested she is "over propped" but the problem occurs at both slow and full revs - although is worse the faster you go! I have also tried running the engine with the covers removed in case it is a lack of air flow around the engine, but I still experienced the dirty mark.

How can I tell if she is "overpropped" and could this be the cause? Help!






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[pete]

Hi Matt
I dont know about the over propping but I would have thought Hunter would have worked that out.and I think all diesel`s would do this.
I have a Hunter 27tk that has the same engine, when I bought it the exhaust had been extended out around 5 inches with reinforced hose to completely clear the transom and I have no trouble. I have recently seen another Hunter with the same mod.

Pete


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[roger]

If your boat is over-propped the engine will not reach design max rpm. If that is the case then the fuel metering pump will be trying to pump in more fuel than the engine can use with black smoke visible especially at high revs. If the engine will reach design speed in neutral but not when in gear you may well be overpropped.
However you can expect some muck to come out of the exhaust anyway and if it washes back over the transom the result may well be dirt anyway.
If the boat is squatting well down in the water you may well be operating close to max hull speed and the revs you are using are doing very little good in speed terms. In that case just ease off a bit and save fuel

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[Cloven]

I agree. My 272 has exactly the same mod and no problems

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[wizard]

I too have a Ranger 245 - 2001. I do not have this problem. The exhaust outlet has an approx 50mm extension away from the transom - is yours the same?
Also how high up the transom is the exhaust outlet centered?
I dont think that the prop is the problem as they fit the same to all.

Geoff

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