prop question

[zindale]

i have a 24 ft pontoon with an 98 115 johnson wide open is 4700 rpms at about 18-19 mph is that about right is a new boat to me it has a 14X13 prop on it now. thanx for your help

 

[walleyehed]

Re: prop question

One 'toon I work on here is a 30ft'r with the same engine and same 14X13 prop, but it will turn 5600 with 6 on board. 4700 is way too low and is basically lugging the engine. If your 115 is a 60 degree looper, we got some problems. 98 was the last year of the crossflow as well, and that's still way low for either engine. which side is the trim button on the engine...port or starboard?
Do we know the tach is accurate?

 

[zindale]

Re: prop question

thanx for reply the trim button is onstrb side mod # J115TSLECM. and tach is the original in dash seems bout right. gonna do a decarb today see if that helps anything.

 

[walleyehed]

Re: prop question

ok, that's a crossflow....5800 is your target RPM.

 

[zindale]

Re: prop question

thanks walleyed i just decarb in yard will tke to lake this weekend and blow it out bought a gps unit at wally worls to check speed for sure and will post results also done comp check all cyls 115 and all firing strong.

 

[zindale]

Re: prop question

well had a nice time on lake this weekend . as i said i decarbed and changed plugs took out and still 4700 max rpms and speed with gps 18.6. so like you said walleyed guess my prob is in my rpms low not prop?

 

[walleyehed]

Re: prop question

I'm showing 37% slip..I think thats a bit high.
I have too many toons around here with 115's to believe that 24ft'r won't let that engine spin that 14X13 on up into the mid to upper 5's...and I'm 3600ft above sea-level.
Your toons aren't full of water are they?
This "may" turn into more of a question as to your engines health, than props... I just have too many around with 115's in the 24-30ft range, and 28ft-up uses the 14X13, and the smaller ones generally end-up in the 15P area.

 

[zindale]

Re: prop question

well toons arent full of water i dont think sounds hollow doesnt seem to lean. i see where maybe motor is at wrong height? plus throttle plates not opening all the way with full throttle maybe not supposed to i have a manual ordered will be here in a bit. and gonna replace hose and bulb assy and rebuild pump for giggles. this prob not as bad as the trouble i had wit my 150 force thought i was moving up a bit lol thanks again for help

 

[zindale]

Re: prop question

well me again one year later and still same problem. was wondering if a bent blade on prop would cause this found 1 blade bout 3/4 in bent in when motor tries to rev it makes a gurgling sound and actually slows down so i back of to 4000 rpms and it cruises fine bout 13 mph is as fast can go . no water in toons pick up front with fork lift and pulled plugs. was going to get prop reworked and buy new one thinking bout a 14x15 is this a help.

 

[The-Machinist]

Re: prop question

The first thing I would address is the throttle plates. If you've got her balls to the wall all plates should be wide open and level. As for the motor "gurgling and losing speed" my moneys on either : the motor is mounted too high, or you have to much s#!t in the front of the boat, raising the rear. Or your prop hub may be spun. But I'm no expert, I just stayed at a holliday inn express last night