Hi!
I have a Hydrolift 23 (a 2000 lbs Norwegian deep V-hull) with a 1999 Mercruiser 4.3 / 262 MAG TBI GEN+. The outdrive is an Alpha One Gen II.
The last 2 seasons I?ve had problems with detonation above 2600 rpm until a couple of weeks ago when I changed the Shift interrupter swich, now the boat runs fine. I mention this is case these detonations could have caused this next problem I have now.
In the troubleshooting leading up the new Shift interrupter switch I have made a compression test - all cylinders within 10-13 bars pressure. I have also tested the fuel pump under load on the water - pressure is fine.
Now that the engine runs ok (no detonation) I have noticed a vibration (you can feel it standing in the boat). The vibration is probably there all the time, but its not noticable until the boat is on a plane which is above 2200 rpm.
Going on the plane I get the same sound and feeling as when the propeller cavitates in high speed and trimmed out. The outdrive is in its lowest position both on the gauge and visually, so I'm thinking actual cavitation is impossible, i.e. can't explain the loss of power when coming out of the water.
The boat should make about 50 mph at 4500 rpm and now I get 38 mph at 4000. When healthy the was a sense of massive power going from 2500 to 3500 and also from 3500 to 4500. Although the engine will go from 2500 to 3500 there is no power surge, it accelerates slowly and above 3500 there is nothing until you look at the GPS with speed increasing slowly in tenths.
The starboard riser is noticibly hotter than the larboard one but the temp gauge reads ok at 170 degrees. The is also a distinct tapping/rumbling noice coming from the rear starboard side of the engine. See link for a recording of the noice at idle (sorry for the Swedish). https://youtu.be/WxY_gv4ANNQ
Any suggestions?
BTW It was through iBoats that I found the solution with the Shift interrupter switch, my mechanic was baffled, so thanks!
I have a Hydrolift 23 (a 2000 lbs Norwegian deep V-hull) with a 1999 Mercruiser 4.3 / 262 MAG TBI GEN+. The outdrive is an Alpha One Gen II.
The last 2 seasons I?ve had problems with detonation above 2600 rpm until a couple of weeks ago when I changed the Shift interrupter swich, now the boat runs fine. I mention this is case these detonations could have caused this next problem I have now.
In the troubleshooting leading up the new Shift interrupter switch I have made a compression test - all cylinders within 10-13 bars pressure. I have also tested the fuel pump under load on the water - pressure is fine.
Now that the engine runs ok (no detonation) I have noticed a vibration (you can feel it standing in the boat). The vibration is probably there all the time, but its not noticable until the boat is on a plane which is above 2200 rpm.
Going on the plane I get the same sound and feeling as when the propeller cavitates in high speed and trimmed out. The outdrive is in its lowest position both on the gauge and visually, so I'm thinking actual cavitation is impossible, i.e. can't explain the loss of power when coming out of the water.
The boat should make about 50 mph at 4500 rpm and now I get 38 mph at 4000. When healthy the was a sense of massive power going from 2500 to 3500 and also from 3500 to 4500. Although the engine will go from 2500 to 3500 there is no power surge, it accelerates slowly and above 3500 there is nothing until you look at the GPS with speed increasing slowly in tenths.
The starboard riser is noticibly hotter than the larboard one but the temp gauge reads ok at 170 degrees. The is also a distinct tapping/rumbling noice coming from the rear starboard side of the engine. See link for a recording of the noice at idle (sorry for the Swedish). https://youtu.be/WxY_gv4ANNQ
Any suggestions?
BTW It was through iBoats that I found the solution with the Shift interrupter switch, my mechanic was baffled, so thanks!
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