DAUNTLESS 180 115-HP Mercury Four-stroke; Gearcase Noise

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Author Topic:   DAUNTLESS 180 115-HP Mercury Four-stroke; Gearcase Noise

whisperpalm posted 07-12-2006 07:59 PM ET (US)
I have a 2004 180 DAUNTLESS with a 115-HP Mercury four-stroke that has a hard time getting on plane with a full tank of gas and a few adults on board. It came with a three-blade 13-1/4 X 16p VENGEANCE propeller--definately over-propped. I switched to four-blade Powertech 13 x14p propeller. Boat pops up on plane like a two-stoke.
Last weekend I had four adults, full tank of fuel, and pulled adults up on wakeboards and slalom skis no problem. Same cruising speed at 4,000-RPM for both props, 25-MPH. Top end was reduced from 40-MPH (5,800-RPM) with the three-blade to 37-MPH (5,900-RPM) with the four-blade. Anyone with this underpowered boat setup may want to consider the four-blade.
I am posting because of a strange vibration heard when using the four-blade propeller. While coming off plane as the boat settles in at 2,000-RPM to 1,800-RPM there is a strange shrill noise coming from the engine/lower unit. It only happens when coming off plane slowly and keeping the engine in gear above the slow idle point. If coming off plane and putting throttle in neutral no noise heard. Took boat to dealer, they checked lower unit and engine and said everything was fine. They thought the noise was a harmonic or vibration caused by the four-blade prop.
Anyone have any thoughts? Hate to give up the four-blade prop due to the improved performance.
jimh posted 07-12-2006 10:01 PM ET (US)
Sometimes when a boat is decelerating the flow of water past the propeller will spin the propeller shaft faster than the engine shaft is turning the propeller shaft. This results in the gear case producing a noise from the clutch dog ratchet. With a four-blade propeller this tendency may be enhanced because the water flow may be able to turn the four-blade propeller better than it could a three-blade propeller.
bsmotril posted 07-13-2006 09:54 AM ET (US)
What Jim says is correct. And this problem is pretty frequent on 4 stroke motors because they have better compression braking than a two stroke. When the throttle is closed, the 4 strokes rpms drop quicker than a two strokes and there's a greater chance of the prop speed over running the engine rpm speed and the clutch dog will ratchet. BillS
acseatsri posted 07-13-2006 08:47 PM ET (US)
I have to agree that it's the boat's forward momentum turning the prop faster than the engine and you're listening to the clutch dog ratcheting. Just pull the throttle back with a slow even stroke and the noise should disappear. 2004 Merc 115 4-stroke owner.
PS- I turn the same 13 1/4 X 16 pitch on my 18 OR (lighter hull)- tops out at 5800 lightly loaded, but fishing is my only purpose for owning the boat.
tmatt posted 07-14-2006 09:20 AM ET (US)
While I can't contribute regarding the noise, I'm happy to hear a prop report on this setup. I run the 2005 version of this hull & motor....and am very pleased with the fuel usage in this day & age. I top out at about 37- MPH at 5800-RPM with 2 adults and a full tank. I'm now interested in testing a 4-blade prop, as I too experience the planing problems when further loaded down.
One question though, does this action on the clutch dog ratchet result in problems or damage to the lower unit? Or is the clutch dog ratchet behaving as designed to prevent damage to the gearcase?
whisperpalm posted 07-15-2006 09:51 AM ET (US)
Thanks to all for your input. Will the clutch dog grinding cause damage over time? The noise does sound like a grinding and or belt noise caused by the engine turning slower that the propeller. Could the noise possible be from the belt due to the prop trying to drive the engine faster than the engine speed?
Mercury technicians and Mercury regional service tech insist the noise is from the propeller causing vibrations. They suggest a Flo-Torque III hub. But they can't tell me if it is compatible with the Flo Torque II hub.
I may return the traditional rubber type hub from Powertech. But based on everyones comments this may not be the cause.
Overall I need to stick with this or another 4 blade prop as the boat is now usable as long as no damage is occuring to the lower unit.


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Author	Topic: DAUNTLESS 180 115-HP Mercury Four-stroke; Gearcase Noise
whisperpalm	posted 07-12-2006 07:59 PM ET (US) I have a 2004 180 DAUNTLESS with a 115-HP Mercury four-stroke that has a hard time getting on plane with a full tank of gas and a few adults on board. It came with a three-blade 13-1/4 X 16p VENGEANCE propeller--definately over-propped. I switched to four-blade Powertech 13 x14p propeller. Boat pops up on plane like a two-stoke. Last weekend I had four adults, full tank of fuel, and pulled adults up on wakeboards and slalom skis no problem. Same cruising speed at 4,000-RPM for both props, 25-MPH. Top end was reduced from 40-MPH (5,800-RPM) with the three-blade to 37-MPH (5,900-RPM) with the four-blade. Anyone with this underpowered boat setup may want to consider the four-blade. I am posting because of a strange vibration heard when using the four-blade propeller. While coming off plane as the boat settles in at 2,000-RPM to 1,800-RPM there is a strange shrill noise coming from the engine/lower unit. It only happens when coming off plane slowly and keeping the engine in gear above the slow idle point. If coming off plane and putting throttle in neutral no noise heard. Took boat to dealer, they checked lower unit and engine and said everything was fine. They thought the noise was a harmonic or vibration caused by the four-blade prop. Anyone have any thoughts? Hate to give up the four-blade prop due to the improved performance.
jimh	posted 07-12-2006 10:01 PM ET (US) Sometimes when a boat is decelerating the flow of water past the propeller will spin the propeller shaft faster than the engine shaft is turning the propeller shaft. This results in the gear case producing a noise from the clutch dog ratchet. With a four-blade propeller this tendency may be enhanced because the water flow may be able to turn the four-blade propeller better than it could a three-blade propeller.
bsmotril	posted 07-13-2006 09:54 AM ET (US) What Jim says is correct. And this problem is pretty frequent on 4 stroke motors because they have better compression braking than a two stroke. When the throttle is closed, the 4 strokes rpms drop quicker than a two strokes and there's a greater chance of the prop speed over running the engine rpm speed and the clutch dog will ratchet. BillS
acseatsri	posted 07-13-2006 08:47 PM ET (US) I have to agree that it's the boat's forward momentum turning the prop faster than the engine and you're listening to the clutch dog ratcheting. Just pull the throttle back with a slow even stroke and the noise should disappear. 2004 Merc 115 4-stroke owner. PS- I turn the same 13 1/4 X 16 pitch on my 18 OR (lighter hull)- tops out at 5800 lightly loaded, but fishing is my only purpose for owning the boat.
tmatt	posted 07-14-2006 09:20 AM ET (US) While I can't contribute regarding the noise, I'm happy to hear a prop report on this setup. I run the 2005 version of this hull & motor....and am very pleased with the fuel usage in this day & age. I top out at about 37- MPH at 5800-RPM with 2 adults and a full tank. I'm now interested in testing a 4-blade prop, as I too experience the planing problems when further loaded down. One question though, does this action on the clutch dog ratchet result in problems or damage to the lower unit? Or is the clutch dog ratchet behaving as designed to prevent damage to the gearcase?
whisperpalm	posted 07-15-2006 09:51 AM ET (US) Thanks to all for your input. Will the clutch dog grinding cause damage over time? The noise does sound like a grinding and or belt noise caused by the engine turning slower that the propeller. Could the noise possible be from the belt due to the prop trying to drive the engine faster than the engine speed? Mercury technicians and Mercury regional service tech insist the noise is from the propeller causing vibrations. They suggest a Flo-Torque III hub. But they can't tell me if it is compatible with the Flo Torque II hub. I may return the traditional rubber type hub from Powertech. But based on everyones comments this may not be the cause. Overall I need to stick with this or another 4 blade prop as the boat is now usable as long as no damage is occuring to the lower unit.