I own a 2000 H340. It is equipped with the 3GM (27 HP)Yanmar and whenever I approach the 3000 RPM mark, diesel exhaust odour starts wafting into the cockpit. The situation worsens with RPM and around 3500 RPM, black smoke becomes visible behind the boat and the odour becomes extremely annoying. The prop is a 3-bladed VariProp (variable pitch) and I'm wondering if it mis-adjusted. At 3000 RPM the boat will do between 5.8 and 6.0 knots, is that about right? The engine has less than 220 hours on it and seems fine in all other respects. Any ideas? Thanks! Eli Toronto
Exhaust smell in the cockpit
- Thread starter Eli14312
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Black smoke is a result of ...
imcomplete combustion or overfueling. You are increasing the throtle but the air fuel mixture deteriorates or the propeller cannot give you any more RPMs. That prop is an aftermarket as the boat does not come from factory with a variable pitch prop. Check a couple of things. Replace air filter, fuel filter and water separator filter. Add a good fuel additive and top off tank. Check the prop for fouling, barnacles and sea growth can impede the prop from attaining or maintaining correct pitch.
imcomplete combustion or overfueling. You are increasing the throtle but the air fuel mixture deteriorates or the propeller cannot give you any more RPMs. That prop is an aftermarket as the boat does not come from factory with a variable pitch prop. Check a couple of things. Replace air filter, fuel filter and water separator filter. Add a good fuel additive and top off tank. Check the prop for fouling, barnacles and sea growth can impede the prop from attaining or maintaining correct pitch.
engine overload???
If you 've checked everthing Benny listed, you probably need to repitch the prop-black smoke is a sign of engine overload, too much pitch to achieve the higher rpms
If you 've checked everthing Benny listed, you probably need to repitch the prop-black smoke is a sign of engine overload, too much pitch to achieve the higher rpms
Possibly A Mixing Elbow
Have you checked your mixing elbow lately? Your description might indicate this problem. Lots of info in the archives concerning mixing elbows and how they become restricted.
Have you checked your mixing elbow lately? Your description might indicate this problem. Lots of info in the archives concerning mixing elbows and how they become restricted.
I Agree with Chuck...
...that you are overloading the prop. 3000/3500 RPM also sounds high for the 3GM. That will cause it to overload, also. When the problem odor starts, it may be because the airflow is obstructed and the boat is drawing the odor back into the cockpit. Higher RPM's will just make it worse and cause overheating.
...that you are overloading the prop. 3000/3500 RPM also sounds high for the 3GM. That will cause it to overload, also. When the problem odor starts, it may be because the airflow is obstructed and the boat is drawing the odor back into the cockpit. Higher RPM's will just make it worse and cause overheating.
Max RPM
I have a 92 35.5 with the 3GM30F and a Max prop. When I 1st got the boat it was way overpropped and would cruise at 6K @ 2200 RPM. Maxprop gave me the correct settings and with it reset it goes 5.8 at 27-2800RPM The max RPM for the engine is 3600 and with a properly pitched prop you should be able to achieve that although I would never run the engine at that RPM unless in an emergency. The best fuel ecomomy will likely be around 2800 but again I do not know the efficiency of the prop. An over pitched prop will cause the engine to carbon up and it is possible to get some blockage even at low hours in this case. I just relaced my exhuast elbow and it made a huge difference.
I have a 92 35.5 with the 3GM30F and a Max prop. When I 1st got the boat it was way overpropped and would cruise at 6K @ 2200 RPM. Maxprop gave me the correct settings and with it reset it goes 5.8 at 27-2800RPM The max RPM for the engine is 3600 and with a properly pitched prop you should be able to achieve that although I would never run the engine at that RPM unless in an emergency. The best fuel ecomomy will likely be around 2800 but again I do not know the efficiency of the prop. An over pitched prop will cause the engine to carbon up and it is possible to get some blockage even at low hours in this case. I just relaced my exhuast elbow and it made a huge difference.
Exhaust smell
I also have the 2000 H340 with about 200 hours on the engine. I too have noticed a slight and occasional exhaust smell but no smoke when motoring and depending on which way the breeze is blowing. The Max RPM for the 3GM30F engine is listed as 3600 and it has a continuous rating of 3400 RPM. The sweet spot for my boat is 2800-2900 RPM and I get between 6.2 - 7 knots depending upon conditions. I have a 3 blade Campbell Sailer prop (15X9X1). When I bought the boat the prop was badly fouled and that is the only time the engine produced black smoke - and lots of it. It sounds like your boat is a little over proped but I would also check for prop fouling, dirty injectors or possibly a mixing elbow that is becoming blocked.
I also have the 2000 H340 with about 200 hours on the engine. I too have noticed a slight and occasional exhaust smell but no smoke when motoring and depending on which way the breeze is blowing. The Max RPM for the 3GM30F engine is listed as 3600 and it has a continuous rating of 3400 RPM. The sweet spot for my boat is 2800-2900 RPM and I get between 6.2 - 7 knots depending upon conditions. I have a 3 blade Campbell Sailer prop (15X9X1). When I bought the boat the prop was badly fouled and that is the only time the engine produced black smoke - and lots of it. It sounds like your boat is a little over proped but I would also check for prop fouling, dirty injectors or possibly a mixing elbow that is becoming blocked.
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