All info below:
ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
Motor not getting up to correct RPM at WOT...
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
78120 A40L 19P (14" X 19") - alluminum 3 blade
3) Current prop diameter and pitch (required).
Above
4) Wide open throttle RPM and speed with an average load (very helpful)
RPM guage not working, never has...working on getting that fixed..but have been told that the recommended range is 4300-4500 WOT for my engine and drive. But by listening to the motor the RPM are staying low, but sounds like it has a heavy load.
5) Engine/drive make, model, year, and HP
GM 250 c.i. Inline 6 cyl, pre-alpha M drive, betweem 1966-68, 160HP NOT the 165HP
6) Boat make model, year, length and weight
1966-68 John Allmand 23ft Cabin Cruiser Solid fiberglass - est. around 3500-4500 lbs. very heavy construction.
I do not have an overheating issue...just replaced exhaust manifold, riser, thermostat housing, hoses. Water flows fine and stays around 140-160 degrees. I have only had this boat for about a year and as I have been restoring it I have found many things not original to the boat. The motor sounds like it has plenty of life and power. When we partially took it apart to put on the new manifold, we looked in and it seems like it has probably been rebuilt in the last decade. Pretty clean. Has lots of power, all cylinders hit good.
However, when I put it in the water and put a load on it I do not get much speed...maybe 10-12 knots. I hit the gas and the motor revs up but really doesnt seem to go much faster. I recently banged up the prop on an oyster bed and need to replace. Should I try a lower pitch? Doesn't lower pitch allow for more RPM?
Also, I put an extra strong throttle return spring on the throttle arm so I may need to do some adjustment there to get more RPM..but is 19 to much or too little pitch for this size of a boat?
Again consider that the RPM guage is not working, never has...working on getting that fixed..but have been told that the recommended range is 4300-4500 WOT for my engine and drive. But by listening to the motor the RPM are staying low, but sounds like it has a heavy load.
In the past though, I have had higher RPMS with the same prop. It could be that I just need to tweak the throttle and linkage on the new manifold setup...but after reading, a boat as heavy as this one seems like it would benefit more from a lower pitch? Also, I am not looking for speed. I would like to be able to do around 15-20knots and have a good plane (which is another thing its not doing very well, never has)
any advice is appreciated.
Robert
ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
Motor not getting up to correct RPM at WOT...
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
78120 A40L 19P (14" X 19") - alluminum 3 blade
3) Current prop diameter and pitch (required).
Above
4) Wide open throttle RPM and speed with an average load (very helpful)
RPM guage not working, never has...working on getting that fixed..but have been told that the recommended range is 4300-4500 WOT for my engine and drive. But by listening to the motor the RPM are staying low, but sounds like it has a heavy load.
5) Engine/drive make, model, year, and HP
GM 250 c.i. Inline 6 cyl, pre-alpha M drive, betweem 1966-68, 160HP NOT the 165HP
6) Boat make model, year, length and weight
1966-68 John Allmand 23ft Cabin Cruiser Solid fiberglass - est. around 3500-4500 lbs. very heavy construction.
I do not have an overheating issue...just replaced exhaust manifold, riser, thermostat housing, hoses. Water flows fine and stays around 140-160 degrees. I have only had this boat for about a year and as I have been restoring it I have found many things not original to the boat. The motor sounds like it has plenty of life and power. When we partially took it apart to put on the new manifold, we looked in and it seems like it has probably been rebuilt in the last decade. Pretty clean. Has lots of power, all cylinders hit good.
However, when I put it in the water and put a load on it I do not get much speed...maybe 10-12 knots. I hit the gas and the motor revs up but really doesnt seem to go much faster. I recently banged up the prop on an oyster bed and need to replace. Should I try a lower pitch? Doesn't lower pitch allow for more RPM?
Also, I put an extra strong throttle return spring on the throttle arm so I may need to do some adjustment there to get more RPM..but is 19 to much or too little pitch for this size of a boat?
Again consider that the RPM guage is not working, never has...working on getting that fixed..but have been told that the recommended range is 4300-4500 WOT for my engine and drive. But by listening to the motor the RPM are staying low, but sounds like it has a heavy load.
In the past though, I have had higher RPMS with the same prop. It could be that I just need to tweak the throttle and linkage on the new manifold setup...but after reading, a boat as heavy as this one seems like it would benefit more from a lower pitch? Also, I am not looking for speed. I would like to be able to do around 15-20knots and have a good plane (which is another thing its not doing very well, never has)
any advice is appreciated.
Robert
