Which prop

[rob 135]

I have a 79 Silverline Comoro with a 1973 135hp Johnson . Has original prop , how do I tell what original is for pitch and size? It runs between 32- 35 mph with 3 adults. New tach on way , old one stopped working. Fresh rebuild on motor don't want to be overworking motor if not needed. I just want to cruise lake ,not fast just ride. What is good prop for this size boat?

 

[steelespike]

Re: Which prop

Get us your present lightly loaded wot rpm and gps speed, when you get your tach.Your prop should have numbers near the base of the blades or under the prop nut. _ _ X _ _ diameter X pitch. Some cell phones have a gps app.
Tell us about your boat size, type,dry weight if possible. The motor needs to be propped to run within its wot rpm range.

 

[rob 135]

Re: Which prop

Boat is 17 ft tri hull . Not sure of weight. It's big and heavy.

 

[Sea Rider]

Re: Which prop

Was that a original factory delivereed prop along engine ? if prop is in excellent performing state, install the tach, go for a wot spin on flat calm no wind water with you alone anmd lightly loaded boat, check max wot achieved, compare readings to factory specs. Will know for sure if over or under propped. Check with a prop shop, they should determine prop diam and pitch if happens not to be stated on prop.

Once you know, can play with pitch to mazimize boat/engine performance to be at or near max factory stated rpm, once there you can cruise at any given throttle position safely.

Happy Boating

 

[steelespike]

Re: Which prop

I think a healthy 135 could produce lightly loaded speeds around 40 on that hull.