Low RPMs on Mercury Mariner 60 ELPTO BigFoot (1996)

[jaxspellinar]

I just got a 25' pontoon with the above engine in it. Currently the oil pump is plugged off and it runs 50:1 mix. It seemingly runs good, but the issue I'm having is that at full throttle, I'm only getting about 3500RPM out of it. The Engine ID sticker says max RPM is 5000. I don't expect to have it run top end, but I'm wondering if that would be normal for full throttle, or if something's wrong.

Thanks!

 

[fitz73222]

What pitch propeller? Should be around 10-11 pitch on a 25' pontoon.

 

[jaxspellinar]

I'm not sure, It's the motor that came with the 'toon. Would it be listed on the prop, or is there a good way to measure it?

 

[jaxspellinar]

I'm getting 13-15MPH at full throttle with minimum weight. At 7-9 adults it's about 12 MPH

 

[faztbullet]

60HP way to small for 25ft toon...and the more people the slower it will be

 

[jaxspellinar]

60HP way to small for 25ft toon...and the more people the slower it will be

I understand the physics, I'm just trying to understand the inability to get the RPMs up.

 

[fitz73222]

Check prop pitch, look on the propeller hub for number between the blades! You can turn a motor 5500 rpm pushing a barge with the correct propeller. They make props for your bigfoot to push slow heavy loads.

 

[racerone]

^^^^---Talk to some prop folks.----Post the diameter / pitch numbers on your prop.

 

[jaxspellinar]

The prop is in pretty rough shape. There isn't anything stamped in or on it except the capital letter "R". I tried to attach a couple pictures, but it keeps giving me an error

 

[jaxspellinar]

What pitch propeller? Should be around 10-11 pitch on a 25' pontoon.

What diameter would you suggest?

 

[fitz73222]

Prop Wizard

turningpointpropellers.com

This assumes that your tachometer is reading correctly and your engine is running normally without any issue. This would be the prop for your engine.

 

[fitz73222]

I tried to cut and paste the actual propeller but it went to the calculater, The prop is a 14" dia X 11" pitch, 3 blade that fits your 4 1/4" bigfoot gearcase.

 

[jaxspellinar]

I tried to cut and paste the actual propeller but it went to the calculater, The prop is a 14" dia X 11" pitch, 3 blade that fits your 4 1/4" bigfoot gearcase.

Thank you, sir! The prop spins freely, do I need to get a new hub kit(?) for the new prop?

 

[racerone]

Most props have diameter and pitch stamped on them somewhere.

 

[jaxspellinar]

Most props have diameter and pitch stamped on them somewhere.

That's what I thought, but I looked all over and in it, but only found the R for the rotation. Unless it was worn off with use. I ordered a replacement 14/11R Prop and hub kit per fitz73222's recommendation. Should have it by this weekend and can find out if I get better performance.

 

[racerone]

Run to a prop shop and have them check the pitch.----Any pictures of this prop ?

 

[jaxspellinar]

Run to a prop shop and have them check the pitch.----Any pictures of this prop ?

I tried to post them earlier, but it doesn't seem to attach them correctly