A Boat Load of Prop Clarity PLease!

[songdog]

A Boat Load of Prop Clarity PLease!

I have a heavily loaded 16ft aluminum boat with a 25 evinrude #25553B. When I put my fat buddy in the boat she struggles to get on plane. CUrrently I'm using a 9x10 prop. What benefit if any will I see by increasing the prop DIA AND Pitch to 9-1/4 X 11? I understand the efects of pitch on RPM @ WOT. My question is what will the extra 1/4" DIA provide. <br /><br /> In my book a $70.00 prop change is cheaper than a new"er" 40HP motor. I'am happy with the Evinrude reliability but I've got a heavy boat full of duck hunting/ Salmon fishing gear. PS. I'm fat too!

 

[jim dozier]

Re: A Boat Load of Prop Clarity PLease!

Re: A Boat Load of Prop Clarity PLease!

I don't think you completely understand the relationship of prop pitch. You will gain no improvement in going to a higher pitch. Performance would be worse. Pitch calculations on any given prop include the diameter so I wouldn't focus on diameter so much in your scenario. You need a prop with a smaller pitch to let your engine rev up to normal operating rpm with fat buddy. Do you have a tachometer on this boat? If by some chance your engine was still reaching max rpm with your current prop and fat buddy (doubtful), then your only recourse would be either bigger engine or smaller buddy.

 

[walleyehed]

Re: A Boat Load of Prop Clarity PLease!

Re: A Boat Load of Prop Clarity PLease!

Well said, jimd....

 

[umblecumbuz]

Re: A Boat Load of Prop Clarity PLease!

Re: A Boat Load of Prop Clarity PLease!

When I put my fat buddy in the boat she struggles to get on plane

Or put her on a plane and take your boat out solo.<br /><br />You'll both end up going faster!

 

[cobra 3.0]

Re: A Boat Load of Prop Clarity PLease!

Re: A Boat Load of Prop Clarity PLease!

Not sure if a lower pitch prop will help much with fat buddy. Sounds like stomach stapling would work for him. <br /><br />Also try moving fat buddy around in the boat.<br /><br />I had a fat buddy in my boat some years back. I cringed every time he got in the boat. Fortunately he stopped the industrial quantites of soft drinks and lost somewhere around 150 lbs!!!

 

[songdog]

Re: A Boat Load of Prop Clarity PLease!

Re: A Boat Load of Prop Clarity PLease!

I'm constantly making sunbtle hints about his weight poor guy ain't seen his feet in years. <br /><br />So I did some more research and determined from this discussion I should consider reducing the prop pitch to increase RPM(assuming they are under the max limit with the current prop). There by more speed and lift will be given. Increasing the diameter only increases engine load for a given pitch.<br /><br /> Of course understanding the RPM is important.<br /><br />Any thoughts on which part # tiny tach is correct for the motor # 25553B?

 

[pwiseman]

Re: A Boat Load of Prop Clarity PLease!

Re: A Boat Load of Prop Clarity PLease!

I have a fair bit of experince with 16' boats running 25s of various flavors. The OMCs will run forever, but they start to strugle on a 16' boat with more than 500 lbs of cargo. Dropping in pitch might help some. The Suzuki DT25s are the best 2 stroke 25 HP followed by Yamaha, Merc and OMC. TOugh to find the Suzuki, and tougher to find somebody to work on them. Fortunantly they are very reliable. I'm actually looking for one of those right now for a backup.