E32 Prop Diameter & Cutless-Prop Distance
I recently repowered my 1978 E32 from an old Yanmar 2QM20 to a new Yanmar 3YM20. The engine purrs but I find my self between a rock and a hard place. The boat has become darn near impossible to reverse to starboard out of my slip and when under power in forward, at speeds above 5.5 knots, there is a significant pull to port. I suspect that the problem is caused by prop wash on the rudder.
The details:
· I changed out the old 12” diameter by 12” pitch two blade prop with a new 12” by 10”. Max RPMS are still under rated (3500 vs 3600 rated). I also replaced the cutless bearing.
· The distance (measured by my diver) between the aft end of the cutless and the forward edge of the prop hub is 4 and 7/8” inches. The shaft is 1” in diameter and, from a previous question on this site, I understand that the proper distance between the cutless and the prop hub is 1”.
· The mechanic installed a shaft extension when he installed the new engine. The shaft extension is 4.25”.
· Now comes the “rub”, I had the diver measure the distance from the center of the shaft, vertically to the hull, at a distance of one inch aft of the cutless. He says it is 5.75 inches (clearly not enough for a 12” diameter prop). At three inches aft of the cutless, he says it is 6.75 inches. At the present location of the prop, he says the clearance between the top of the prop and the hull is 1.75 inches. If these measurements are true, it looks like I would need to go to a 10 inch diameter prop in order to obtain the 1” separation between cutless and prop hub.
· Your guess is as good as mine as to why the bottom cleaner put the zinc where it is. And as to why didn’t I measure clearances, etc, when the boat was out of the water? Good question. I have been beating myself up for that one already.
Question for E32-II owners: What is the diameter of your prop and what is the distance between the cutless bearing and propeller hub?
See pictures attached.
I recently repowered my 1978 E32 from an old Yanmar 2QM20 to a new Yanmar 3YM20. The engine purrs but I find my self between a rock and a hard place. The boat has become darn near impossible to reverse to starboard out of my slip and when under power in forward, at speeds above 5.5 knots, there is a significant pull to port. I suspect that the problem is caused by prop wash on the rudder.
The details:
· I changed out the old 12” diameter by 12” pitch two blade prop with a new 12” by 10”. Max RPMS are still under rated (3500 vs 3600 rated). I also replaced the cutless bearing.
· The distance (measured by my diver) between the aft end of the cutless and the forward edge of the prop hub is 4 and 7/8” inches. The shaft is 1” in diameter and, from a previous question on this site, I understand that the proper distance between the cutless and the prop hub is 1”.
· The mechanic installed a shaft extension when he installed the new engine. The shaft extension is 4.25”.
· Now comes the “rub”, I had the diver measure the distance from the center of the shaft, vertically to the hull, at a distance of one inch aft of the cutless. He says it is 5.75 inches (clearly not enough for a 12” diameter prop). At three inches aft of the cutless, he says it is 6.75 inches. At the present location of the prop, he says the clearance between the top of the prop and the hull is 1.75 inches. If these measurements are true, it looks like I would need to go to a 10 inch diameter prop in order to obtain the 1” separation between cutless and prop hub.
· Your guess is as good as mine as to why the bottom cleaner put the zinc where it is. And as to why didn’t I measure clearances, etc, when the boat was out of the water? Good question. I have been beating myself up for that one already.
Question for E32-II owners: What is the diameter of your prop and what is the distance between the cutless bearing and propeller hub?
See pictures attached.
Attachments
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Shaft Coupling & Extension.jpg -
Prop & Shaft.jpg