New 15x17 pitch prop on Merc 165 L6

[EZDuzIt]

Just put a new 15x17 pitch prop on my 1976 Apollo Tri Star with the GM 250 cu in (4.1L) straight six. Man this prop is just nuts on. WOT at 4500 rpm and 40 mph. Cruises real nice at 3000-3500 rpm at 25-30 mph. Good hole shot and plains right out, even leaving the outdrive in the trimmed position. Drop the outdrive down and it takes off like a V8. This is a fantastic replacement for the stock 14x19 pitch prop. Didn't loose any top end and the hole shot is definitely improved. I did have to grind my trim tab back about a 1/4 inch so that the larger diameter prop would clear with room for expansion. I have about a 1/2 inch clearance now which is fine. Very, very happy I did this.

 

[Scott06]

Just put a new 15x17 pitch prop on my 1976 Apollo Tri Star with the GM 250 cu in (4.1L) straight six. Man this prop is just nuts on. WOT at 4500 rpm and 40 mph. Cruises real nice at 3000-3500 rpm at 25-30 mph. Good hole shot and plains right out, even leaving the outdrive in the trimmed position. Drop the outdrive down and it takes off like a V8. This is a fantastic replacement for the stock 14x19 pitch prop. Didn't loose any top end and the hole shot is definitely improved. I did have to grind my trim tab back about a 1/4 inch so that the larger diameter prop would clear with room for expansion. I have about a 1/2 inch clearance now which is fine. Very, very happy I did this.

Proper pitch for the application is everything. You are better to be a tad underpropped vs overpropped.

What is the reccomended WOT for that engine?

What type of prop did you buy - Black max?

 

[EZDuzIt]

Proper pitch for the application is everything. You are better to be a tad underpropped vs overpropped.

What is the reccomended WOT for that engine?

What type of prop did you buy - Black max?

Went with a Rubex prop. Brand new with the hub kit it was $180 bought locally from a local small business, which I try to do as much as possible. The guys at Precision Propeller here in Spokane, WA really know their stuff. Told em what I had, what I wanted performance wise and they recommended my prop. Book says WOT should be 3800-4400. I've read a lot of other blogs, watched videos, talked to a few reputable shops and they all say that engine and gen 1 Mercruiser outdrive set up can handle 4700-4800 rpm at WOT just fine without hurting anything. The guy at the prop shop said I should get about 4500 rpm with this new prop and that's exactly where it leveled out at WOT perfectly trimmed out.

 

[Faztbullet]

The additional diameter helps as prop blade hold more water, this helps in mid range to hold boat "up" at slower speeds

 

[Sea Rider]

It's a night day boating diffrence propping right a motor to rev at its max or slight over their max wot rpm range as currently loaded to achieve an oustanding hole shot. Do you boat with a fixed or variable load ?

Happy Boating​

 

[EZDuzIt]

It's a night day boating diffrence propping right a motor to rev at its max or slight over their max wot rpm range as currently loaded to achieve an oustanding hole shot. Do you boat with a fixed or variable load ?

Happy Boating​

Fairly variable. Primarily we use it for fishing but we do occasionally tow friends and kids on a tube. This prop really holds the engine rpm well in tight turns with very little need to increase throttle. For how we use the boat this prop is a perfect middle ground. I'm very impressed by how easily the boat plains out. About half throttle even leaving the outdrive in the plaining position it gets right outta the hole and levels back out.