Prop suggestions

[Zman1661]

I have a 1990 searay bowrider 180. It is 135 HP Mercury black max outboard. I just purchased this it currently has a 5 1/4x19 pitch ss Mirage. First time out i'm getting 4200 RPM If I trim it out just right and about 42 miles an hour. WOT for this engine is 5000 to 5500 from what I read. Was thinking about going to aluminum 14 1/2 x 17 pitch. I was told that I would gain 200to 400 RPM from the pitch change and another one to 200 going from SS to aluminum. Just wondering some thoughts I'm going out this weekend to buy the 17 pitch prop and try It. Any ideas on what this will do to my TopSpeed and hopefully I don't spin too many RPMs I don't want to damage the motor

 

[Maclin]

Welcome aboard!

Your thinking seems reasonable, should get you much closer to the RM range you need to get to. I hope it wakes it up some, Good luck!

 

[jimmbo]

I suspect tach is out to lunch, and one cylinder is not pulling its share

 

[Zman1661]

Well that's a scary thought I will be doing a compression check today. Assuming that Check sent out I will update I know that the motor seems to run great

 

[Zman1661]

OK some good news Compression check everything's good Cold 106 across the board warm 110 across-the-board give or take 1 pound I think that's pretty good for a 20-year-old engine it's going in the water tomorrow