Hi all, it's been a while, just come out of winter hibernation & getting the boats ready for hopefully a good summer! Need a bit of advise on what size prop, for all round performance, I should fit. Set up as follows; Walker Bay 340 ( 3.4mts ) with 2007 15hp 4 stroke Mercury with electric start. Normal crew of two but occasionally Four up for short trips. Thanks.
In truth you need to have a starting point... what do you use currently?
General advice though most 15hp motors will have a 9" or 10" prop as standard. This seems fine for use on most inflatables but yours I think is a hard hull so perhaps 10" or 11" for yours when two up. Doubling the weight will often bog down a 15hp so you might not get a prop that's ideal for both load requirements.
Start point would be to see what your current prop wide open throttle revs are with the boat loaded normally and whether that falls within the WOT rev range specified for that engine.
Once you've got that, have a look on Mercury's prop selector: https://www.mercurymarine.com/en-gb/...tion#/step-one
Thanks for the prompt reply's I've just checked the prop I was running last year 9 x 8P. The boat planed pretty quick with two even three up, seemed to run within the rev range at WOT okay. Would going to a 9 1/4 x 10 help on fuel economy at all, not that i'm tight or anything: but doing a 100km a day in the summer is a common occurrence.
If you are in the right rev range approx with an 8" pitch probably going to a 9" would be as far as I'd go.... 10" may spoil the performance when at your max load.
Sadly every boat/outboard/load combo is diferent so it's always a bit of trial and error.
but doing a 100km a day in the summer is a common occurrence.
