2120 150TXRC prop?

[johnsw]

Looking to find out what prop folks might be using with similar hull / engine. Curious what WOT RPM you may be reaching.

For a while now (years), my WOT max RPM has been running a pretty consistent 4800 rpm. The last inch or so of throttle produce no increase in RPM. Adjusting trim angle doesn't help much. No issues at idle and engine seems to be running fine at full throttle, but not really sure I'd hear or feel an engine miss or anything at that point. Acceleration is good. Ignition system was gone though last season to diagnose and correct failing stator problem. Carbs were also overhauled in the process. I've checked WOT static timing and adjustments and they look correct. Compression check is one of the few remaining things I can think of to check.

Have always had the same spec 3 blade SS 14.25 x 16 prop that came with the boat when new back in '04. Wondering if it may be time to try tweaking the prop to see if I can get some rpms back if everything else mechanically checks out.

The yam manual has WOT spec as 4500 - 5500 rpm, so technically I'm in spec. But I'd like to be closer to the higher number rather than being on the low side.

Any thoughts?

Thanks

Followup question to anyone who has done prop testing? Reading that too much pitch loads the engine and lowers WOT rpm, does that give the symptom of having a dead spot on the throttle where the rpm goes no higher? Visual check looks like the throttle plates are operating full range of the throttle control.

 

[DSW]

Hi,
Similar but not exactly the same, but the lesson learned was the prop that came with the boat had too much pitch and going from 17 to 15 gave better performance numbers. I think our hulls are the same. Ken at Propgods helped me get the right prop.

I've posted the following before, hope this help you figure out what's best for you. Lots of good info on the site that's helped me.


1997 2110, Yamaha 175 carb Salt Water Series II

Old Prop
17M
RPM Speed Slip
4000 27
5300 38 17
on plane 4000

New Prop
Q3 15p
RPM Speed Slip
1000 4.4 45
2000 7.7 49
3000 11.8 49
4000 25.1 19
5000 34.8 8
5500 39.0 7
on plane 3400

I just finished putting on a fuel flow meter and don’t have mpg numbers. Others with same hull and motor have said 4000 rpm 2.4 mpg

 

[johnsw]

Thanks. I figured rpm should improve, but it's not clear yet if it would also return some or all of the throttle response where today I'm getting nothing (3/4 up to full throttle stop). I've run it this long like it is and so far none of the usual maintenance and various repairs that have been made has changed it either way. So just not sure if I'm spinning my wheels looking for an engine problem or it's as simple as just needing a prop change. But it's that dead zone on the throttle that has me going.

I did put my spare prop on a few years ago just for hoots, but it's the same 14-1/4 x 16. No difference, but didn't really expect much else.

 

[johnsw]

After sleeping on this one a bit more, I seem to have circled back to the carbs.....again. Despite last season when I had them apart, they looked clean and had no gunk or visible varnishing. Just the same, I shot cleaner through all the ports and blew everything out with compressed air as I had them apart. Put in all new gaskets (yam kit) and double checked float height.

It's running and usable, so I may just use it another season as is and plan to do the carbs again at some point, unless I get ambitious or it seems to be getting worse.. But next time use carb cleaner in an ultrasonic cleaner. For now, I know the limitations of what the engine can do.

But if anyone can think of anything that may help, let me know.

Thanks again

 

[DSW]

Hi johnsw,
I searched the site for 2120 prop and found a lot of posts with different engines but most having changed to a 15 pitch prop with varying diameters. A few had 17 pitch props but they had 200 or more hp.

I think you have the low end hp for this hull and the rpm you've reached is the max your hp can turn your prop. I think you have to go to a lower pitch to raise your rpm and you may not have an engine issue. When I was prop testing the goal was to get to 5300 to 5500.

Here's another person asking a similar question to yours, and they have a lower pitch prop and are getting a few more rpms.

I'd search this site for 2120 props and see what others have written and I's also email propgods and get their recommendation and price on a different prop.

Good luck

mrammo

Post subject: 2120 prop recommendation Post Posted: Sun May 12, 2019 1:31 pm

Have a 2007 2120 pilot house with a 2005 Yamaha 150 TXRD 2 stoke carb. Has Yamaha Reliance 14 1/2 x15 prop. Engine is mounted two holes from bottom. Cavitation plate is level with bottom of boat. I’m only getting 4900 to 5000 rpms out of it. Hitting about 30mph. This is with a light load. From reading from other reports I feel I should be getting more out of this motor. Anybody have this same setup and what are your performance numbers. Any advice on a different prop or try a hydrofoil like a permatrim or doel fin. Motor just as recent service. Appears to be running real well.
Thanks
Mike

 

[johnsw]

Thanks so much for the info you've provided, DSW. I was also kicking around that what I'm getting might just be the best I can do at 150hp. Throttle flattens out since I just don't have the umph to turn this fully loaded prop any faster. But wasn't sure if I was just overthinking it. I might consider trying a 15 next season.

I'll take some more time to search the forums again.

Since I'd rather spend time fishing and not doing engine chores, decided I'm just going to run it. It is what it is. As long as it starts every time and gets me home without a tow the same number of times I leave the dock, then all is good.

Thanks again