what size prop for 30hp johnson?

[bballfan77]

I have a j30elsod on a 16.5 ft Grumman center console. I'm gonna put the total weight at 1700lbs this includes me and fishing gear, batteries etc. Currently 4200rpms and 10mph is all I'll get to. This with a 10x13 prop.
Thanks in advance. Jeff

 

[steelespike]

Re: what size prop for 30hp johnson?

I'm assuming that is a 2 cylinder 30 from the 90s
I think a 13" is too much prop for 1700 lbs. Maybe an 11" would do better.
At 10 mph your not planing so 4200 Doesn't mean much to evaluate your setup.
If you can lighten it up and get a planed wot rpm and speed by gps we can tell better what you need.

 

[jestor68]

Re: what size prop for 30hp johnson?

You're more than a thousand rpm down from the bottom of your rpm range.

Visit the iboats prop section and select(recommended) a Solas Amita 11 X 9 prop. Be sure to order the Solas thrust washer with it for proper installation. That prop(the smallest listed) will gain about 800 rpm and get you close to the minimum rpm for your motor.

You won't set any speed records, but it will get that heavy (for a 30 hp) boat planed off and moving at a decent speed.

 

[bballfan77]

Re: what size prop for 30hp johnson?

Thanks fellas......I'll try to lighten her up first and see if I can plane it out a bit. I also have a 9.9 kicker on the transom that by itself gets me to 7 MPH GPS sog.
I'll report back thanks!

 

[steelespike]

Re: what size prop for 30hp johnson?

You're more than a thousand rpm down from the bottom of your rpm range.

Visit the iboats prop section and select(recommended) a Solas Amita 11 X 9 prop. Be sure to order the Solas thrust washer with it for proper installation. That prop(the smallest listed) will gain about 800 rpm and get you close to the minimum rpm for your motor.

You won't set any speed records, but it will get that heavy (for a 30 hp) boat planed off and moving at a decent speed.

The boat wasn't planed so the rpm doesn't indicate true wot rpm. The boat needs to be planed in order to make an accurate prop selection.The 13 is probably too much even if the boat was at an average load.

 

[Swinerton]

Re: what size prop for 30hp johnson?

30hp trying to move 1700lbs through water....... Ouch. Boat really needs a 40hp minimum IMO.