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Hi all, I thought I would look to the A4 community for some help on the low RPMs I am experiencing.
I have a 76 Tartan 30 with the original A4 and original 2 blade prop. This is our fourth season with the boat and we enjoy it very much. Since we have had the boat I never felt I was getting full power and RPMs out of the A4 although it may have been better in the first year. I installed a tach on the engine last summer to see how it was performing.
In reverse I get about 2000 RPM max and in forward only about 1300 RPM. In reasonably calm water the engine manages to push the boat along anywhere between 5.7 and 6.2 knots depending on the conditions. I occasionally can get the RPM up to 1500 but it seems to go back to about 1300 over a couple of minutes. At low idle, about 500 RPM, the boat will do about 2.5-3 knots in forward.
I know that the prop is over pitched for the engine. It is either a 12x8 or 12x9 prop based on the documentation I have and what I have read.
I have been through the forums, postings and troubleshooting information.
The engine starts easily and runs well. I have tested the compression several times and have 90-100 PSI in each of the cylinders. The carb was replaced in 2007 and I thought it might be some dirt in the carb so I took it apart and it seemed very clean. I cleaned it and reinstalled it and it seems to be working fine. In neutral the engine responds very well to the throttle. I have 2 filters - a sierra water separating filter that I think is 21 microns and a second filter before the fuel pump. I retimed the engine which seems to have helped a bit. It is idling a bit better at least. I have electronic ignition and an electric fuel pump. I changed the plugs (champion 12rc) recently and they seem to not be fouling at all. The previous plugs seemed fine as well.
The prop does not seem to be fouled in any way. I can turn the shaft easily from inside the boat and I seemed to have the same performance right after spring launch when the bottom was nice and clean.
I had the sierra filter installed by our local marine mechanic 3 years ago. I am not sure if this could be the cause the issue. I did inadvertently put in some ethanol fuel (10%) last year and still have at least some in the tank. When I pumped out some gas I could definitely see some separation.
Would some type of air leak in the fuel system be the cause? Is there anything else I can check or should check or is this the best I can expect with this prop? My plan is to eventually get an indigo 3 blade prop which many A4ers seem to be getting good performance from.
The engine gets us in and out and has never caused any real problems but I would like to get it performing as well as it can and have additional power when required. Any advice or direction would be appreciated.
Thanks,
Geoff
I have a 76 Tartan 30 with the original A4 and original 2 blade prop. This is our fourth season with the boat and we enjoy it very much. Since we have had the boat I never felt I was getting full power and RPMs out of the A4 although it may have been better in the first year. I installed a tach on the engine last summer to see how it was performing.
In reverse I get about 2000 RPM max and in forward only about 1300 RPM. In reasonably calm water the engine manages to push the boat along anywhere between 5.7 and 6.2 knots depending on the conditions. I occasionally can get the RPM up to 1500 but it seems to go back to about 1300 over a couple of minutes. At low idle, about 500 RPM, the boat will do about 2.5-3 knots in forward.
I know that the prop is over pitched for the engine. It is either a 12x8 or 12x9 prop based on the documentation I have and what I have read.
I have been through the forums, postings and troubleshooting information.
The engine starts easily and runs well. I have tested the compression several times and have 90-100 PSI in each of the cylinders. The carb was replaced in 2007 and I thought it might be some dirt in the carb so I took it apart and it seemed very clean. I cleaned it and reinstalled it and it seems to be working fine. In neutral the engine responds very well to the throttle. I have 2 filters - a sierra water separating filter that I think is 21 microns and a second filter before the fuel pump. I retimed the engine which seems to have helped a bit. It is idling a bit better at least. I have electronic ignition and an electric fuel pump. I changed the plugs (champion 12rc) recently and they seem to not be fouling at all. The previous plugs seemed fine as well.
The prop does not seem to be fouled in any way. I can turn the shaft easily from inside the boat and I seemed to have the same performance right after spring launch when the bottom was nice and clean.
I had the sierra filter installed by our local marine mechanic 3 years ago. I am not sure if this could be the cause the issue. I did inadvertently put in some ethanol fuel (10%) last year and still have at least some in the tank. When I pumped out some gas I could definitely see some separation.
Would some type of air leak in the fuel system be the cause? Is there anything else I can check or should check or is this the best I can expect with this prop? My plan is to eventually get an indigo 3 blade prop which many A4ers seem to be getting good performance from.
The engine gets us in and out and has never caused any real problems but I would like to get it performing as well as it can and have additional power when required. Any advice or direction would be appreciated.
Thanks,
Geoff
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