Prop ? for a 16' aluminum/55hp motor?

[bobandpeni]

Hi folks!<br />I've got a 16' aluminum crestliner with a 1969 Johnson 55hp outboard. I've got a 13 1/4" by 17" prop on the motor. Does anyone have a similar setup that would be willing to share their experience with props? I'm on my second prop now and would really like to be able to get somewhere in the 5000 rpm range with the third prop. Right now I'm getting about 2500 rpm (assuming my pulse is set correctly - topic of another post right now). Thanks in advance!!!!

 

[mikeyzx2]

Re: Prop ? for a 16' aluminum/55hp motor?

Does it sound like it's only turning 2500? It should be screaming at 5000. And are you sure you're not dropping a cylinder?

 

[bobandpeni]

Re: Prop ? for a 16' aluminum/55hp motor?

Mike,<br />I've got to resolve the pulse question before I can be SURE of what rpm I'm turning. My motor has a 12 stator alternator and therefore should be a 6 pulse tach, but there has been some debate as to what my tach should be set to (5 or 6 pulse). My experience is quite limited when dealing with outboards (2 outings only) and my motor is so quiet I really can't be sure what speed my motor is turning - this is why I bought a tachometer in the first place. <br /><br />Is it your opinion that the 17 inch pitch prop should be allowing me to achieve 5000 rpm? <br /><br />Thanks!

 

[mikeyzx2]

Re: Prop ? for a 16' aluminum/55hp motor?

Bob, really a couple things go into effect concerning whether or not the prop should get motor to hit 5000: type of hull, weight with typical load. There is a topic in the FAQ's concerning prop selection. The reason I ask about the RPMs is because if the motor's happens to be losing a cylinder when at WOT you'll never know if the tach's working. By the way what RPM is the tach showing at idle? <br /><br />The 17P might work out fine, but as I mentioned alot depends on the boat. I'm running the same size prop as you on an 85HP V-4, and like you I'm dealing with tach issue so I myself might not have the correct prop, but I have to get set up and test run to see what RPMs I'm running at WOT to see.

 

[bobandpeni]

Re: Prop ? for a 16' aluminum/55hp motor?

Mikey,<br />The motor is running really smooth. It Idles at about 900 rpm. I changed the plugs and all show normal combustion so I would say that the chance of losing a cylinder is remote.<br />Through another thread I think we've resolved that the tach is set correctly. I have a 12 pole stator and my tach is set to 6 pulses.<br />I have an aluminum vee hull, no idea of the weight, but the load is probably about 600lbs once 2 adults, 12 gallons of fuel in 2 tanks and other stuff is added in.<br />Thanks for your reply,