Original prop optimax

[Muskie60]

Does anyone know what the original prop was on a 2007 Mercury 115 hp optimax. Currently it is is stainless steel prop with no markings for pitch or diameter. I want to get a backup prop.

 

[QBhoy]

It very much depends on what boat it’s attached to. There is no such thing as a standard issue prop for any engine. They are matched to the whole set up and boat type etc.
What boat is it and I could take a guess at it within a couple of inches

 

[jimmbo]

Take the prop off the motor and examine every inch of it, the info is on there
What is the Engines WOT rpm range, and what rpm are you getting with your current prop?

 

[Texasmark]

Take the current one to a prop shop and tell them you want an XYZ replacement for similar performance. Expect performance to be different if you lowball the extra prop and go in aluminum.

 

[Muskie60]

Thanks texasmark

 

[Muskie60]

It very much depends on what boat it’s attached to. There is no such thing as a standard issue prop for any engine. They are matched to the whole set up and boat type etc.
What boat is it and I could take a guess at it within a couple of inches

My motor is on a lowe fm175. I measured the prop looks like it's 13.25.

 

[Muskie60]

Take the prop off the motor and examine every inch of it, the info is on there
What is the Engines WOT rpm range, and what rpm are you getting with your current prop?

I'm new to matching the best diameter and pitch for whatever performance I want. But the maximum rpm marked on motor mount is 5750. I'm going to Canada in 2 weeks I'll have to check rpm. I'm pretty sure my maximum speed was around 42 or 43.

 

[QBhoy]

My motor is on a lowe fm175. I measured the prop looks like it's 13.25.

Hi
that will likely be the diameter you are measuring. It’s really the pitch that’s the game changer.
As Jimbo says, there will be a mark on it. If it’s the standard black max merc prop usually found, it will either be stamped between the blades somewhere or perhaps more likely inside the hub behind where the big nut and locking washer are. It will say something like 13x21 or similar. 21 being the pitch and 13 being the diameter.
Being the smaller gear case, it’s likely about 13” or under diameter and I’d guess at a estimated 18-22 pitch for starters. Likely towards the higher end.

 

[Muskie60]

Okay thanks. Yeah nothing marked on the blades and not in the the hub near the nut. I wonder if it's marked where the hub hits the ' lower unit'. Thanks that's a good start I thought the pitch might have been less, I was just guessing.

 

[QBhoy]

Okay thanks. Yeah nothing marked on the blades and not in the the hub near the nut. I wonder if it's marked where the hub hits the ' lower unit'. Thanks that's a good start I thought the pitch might have been less, I was just guessing.

It will really depend what the boat was used for really. If it was used for towing it might have a lower pitch, but generally the range I mentioned, it would be in there somewhere.
The prop should be marked somewhere on it. Would be very unusual not to be. Hard to see sometimes.

 

[Muskie60]

Thanks, appreciate it. I'll take a closer look.