Is it the prop pitch or something more...?

[Kamikazeedragon]

Hey Guys,

I have a 2012 Lowe Pontoon. 2 toon. I have a 75hp Mercury 4 stroke outboard. The boat is about 23 1/2 ' long. When I first got it, I would only get about 8mph out of her and even then, I was pushing around 4 1/2 to 5 RPM. I thought it might be the prop as the pitch was only about a 13. I got a 17 pitch and replaced it. Now I can get up to 15MPH with a WOT. Now I've had issues with this engine, everything from a water lead on the sending unit of the gas tank and recently replaced the lift pump. My question is, should this engine be pushing the boat at least 20 MPH? I'm not looking to go really fast, I know its a pontoon, but just curious if I need to look at a higher pitch prop or maybe there is something wrong with the engine?

TIA

 

[racerone]

What RPM do you get with the 17" pitch ?----I think 17" pitch is too much.----I do not believe you want more pitch here.----Hurry and read up on props and boat speed.----Or talk to your local boat experts.

 

[ahicks]

Yes, something in the low 20's would be about what I would expect as well.
If the engine is starting easily, and idling smoothly, and seems to be running OK at a constant rpm, I would guess it's fine. If it seems like it has a miss, or it's surging, it's not OK....

That 13" prop should have been close/about right. The 17p is likely way big - if - we don't have something weird going on, which I believe may be the case.

Are you sure about the rpm's readings? Is this a new tach?
You can turn them up to 6000rpm, but a better target rpm would be about 5500.

You say you picked up quite a bit of speed going to the 17". Where are your rpm's now?