Strange Issue With Driveshaft After Changing Water Pump

JohnMetta

Cadet
Joined
Jul 10, 2013
Messages
14
First off the serial number of my 1998 Mercury 115hp 2stroke Outboard is OG722825. Just bought a water pump kit and I changed it exactly how the service manual states. I took the Lower Unit out in Forward gear and sid it right back in with no problems at all. Now I'm getting a strange vibration at about 1100 RPM's in gear and it lmost feels like the shaft or gears are grinding. Or this could be completely normal. I'm not sure. I did not notice it before I changed the water pump. Also I'm running at 130 degrees. Is this normal?

Thanks for your help.
 
Last edited:

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,135
Re: Strange Issue With Driveshaft After Changing Water Pump

130 is low unless you are talking celcius.
You should check your thermostats are closing properly and any gaskets on it a sound.
Grinding sounds awful for it.
Does it select neutral/reverse ok?
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,778
Re: Strange Issue With Driveshaft After Changing Water Pump

Vibration not normal. Tstat starts to open at 143F with full open being 10-15 degrees more. Not much you could have done to screw anything up if you had the manual and followed it. Biggest problem is usually the shift linkage gets mis-aligned but you said that went back together ok, or you can't get the drive shaft back in the last 1" because the splines aren't lined up; or the last 1/4" because you put a blob of grease on top of the drive shaft and it's keeping it from seating all the way in the powerhead. Apparently that went ok too. The water tube is fixed now so that's hard to screw up, but it is not a vibration causing element and you said your temp was 130, low as Bosun mentioned and yes it is. You very well didn't give your engine time to warm up to stat open temp.

Drain your lower unit oil and check color and for debris. You should have a magnet on your lower....drain screw. A little bit of metal filings are normal. Oil should be dark blue-black if using Quicksilver...no milky, or chocolate looking oil. Good time to change it anyway. WW has it in the Quicksilver brand, premium grade, with the pump and all.

What are you running for a prop and what have you possibly hit with it? If all else checks out, I'd take a close look at the prop. What type, material and pitch? What boat are you running it on? 1100 is just over idle rpms.

On mine, when I use my heavy SS prop with a lot of pitch (24P Ballistic XP with engine gear ratio of 2.33) I get what's called "clutch dog rattle" at and around that rpm. The clutch dog is around the prop shaft in the lower unit and is what connects with F, R, or no gear to drive the shaft when you select a gear with the shift lever. The big prop and the engine get out of rpm sync and it causes the prop pressure on the prop shaft to bounce back and forth causing a rattling or clunking sound. Merc says it hurts nothing and I agree as those gears are high tensile hardened, but the noise is annoying. When I put on my lesser pitched SS prop I don't hear it, or if running the big one just speed up slightly till it quits. The biggest annoyance is driving on the trailer so I just do a lot of shifting F-N to get lined up, control the boat speed, and minimize the rattle.

Not much else man.

Mark
 

JohnMetta

Cadet
Joined
Jul 10, 2013
Messages
14
Re: Strange Issue With Driveshaft After Changing Water Pump

The shifting and gears are fine. I believe I am getting the "clutch dog rattle" that you are speaking of. I think I may be a little paranoid on this one but I just wanted to make sure. Its on a 1998 Searay Bowrider 180 OB. Not sure about the prop. Looks like whatever came stock. Ive noticed if I ease the RPM's down slowly its a lot less than if I go from high RPMS to low very quick. I still am running below 130 degrees F. At about 3-4k RPMs im at about 130 and will slowly creep up as time goes on.
 
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