Noisy Prop

[lfb123]

I wrote I boats about this as I purchased the prop from them and instead of answering me they sent me here. I bought a new SS Michigan Wheel prop from I boats to replace my aluminum prop. Used exact replacement pitch, etc. from the charts at Michigan Wheel site and here. Motor is a 50HP Johnson 2000 model. When the engine is placed in gear at the first click (slow idle in gear) there is a loud clicking or tapping noise coming from or thru the engine. It is so loud I can hear it from the bank when my son is loading the boat. I put the aluminum prop back on and it did this for a few minutes then went away. Put SS prop back on and the noise came back. I also changed gear oil with prop and used type dealer recommended. It only does this when slowly idling along and when the throttle is increased it quits. Performance is great at any speed other than idle and the boat runs better, planes better and does not cavitate. I have never had a SS prop before and was wondering if this is normal or is something out of balance, etc. As I said I tried contacting I boats to see if I needed to swap out and they sent me here. Thanks for any help!

 

[tommays]

Re: Noisy Prop

I can think of two things <br /><br />1. is the new prop hitting the steering trim tab ?<br /><br />

<br /><br />2. is the new hardware correct (thrust washer ect)so the prop is not rubbing on the gear case ?<br /><br /><br />tommays

 

[walleyehed]

Re: Noisy Prop

Could be putting enough load on the gears that if the shift cable is slightly out of adjustment, it's clicking, then clunking in...

 

[Texasmark]

Re: Noisy Prop

I have the exact same problem and it happened when I installed my latest SS prop which has a lot of pitch and is quite a bit heavier than it's predecessors.<br /><br />I bought time with a local Merc dealer's mechanic (tried to he wouldn't accept payment) so I bought a bunch of oil and accessories to compensate the dealership for his time (my choice).<br /><br />As the story goes, in my case anyway, the teeth of the gears in shift dog in the lower unit are rounded somewhat and also have the ability to have a lot of slop since in Forward gear, the prop can freewheel (called a freewheeling clutch in agricultural equipment) any time it is driving, not being driven by the engine.....that's the clicking noise you hear when you put the stopped engine in F and rotate the prop in the direction that produces the noise. Why propeller drives are built to do this I have no idea. I know why you do it on ag equipment; you have a big machine behind you and it is running and you can stop your engine faster than it can unwind. I guess the prop is screwing through the water and back drags when you pull the throttle back and this keeps it from locking up the gear train and among other things stopping the boat too fast.....like it would cause the bow to nosedive.... might cause you to take water over the bow without it.<br /><br />He continued: When going into gear at idle, or coming down to idle just prior to disengagement (N) the turbulence caused by the large pitch and the weight of the prop are the cause. He said aluminum is light enough that it wouldn't do it. I said that I had 2 prior SS props and they didn't do it; but this beast that's on there now does.<br /><br />Continuing: Said that it won't hurt anything, even though it sounds terrible but I have chosen to do this:<br /><br />Rather than go back to my old props I just give it some throttle as soon as I put it in gear and like you said, it doesn't do it. If I only want to run slowly, like loading onto the trailer, I make several trips into F and back to N till I get positioned on the trailer....works ok for me.<br /><br /> In coming down (from higher rpm's), I don't stop just before N, I reduce to about 1500 rpm's, let the following wake tuck in, and then go directly to N or keep the rpm's up over 1000 in gear....about 650 is spec idle in F on my engine.<br /><br />HTH<br /><br />Mark

 

[astro1]

Re: Noisy Prop

I go with Walleyhead.<br />It sounds like the shift cable is slightly out of adjustment,theextra load from the weight of the stainless prop takes a little more to get it to go into gear and stay..

 

[lfb123]

Re: Noisy Prop

I will check both this weekend. Its not "clunking" into gear though. It shifts as smooth as it always has. The thing that has me wondering though is it did it with the aluminum prop for a few cycles when I first put it back on then quit and didnt do again until I put SS back on. As far as the trim tab its not hitting it and I used the hardware from the other prop. All that was there was a washer, nut and cotter pin. The splines, rubber, etc were built into the SS prop just like the AL one.

 

[walleyehed]

Re: Noisy Prop

Make sure the thrust washer is on the shaft before you put the prop on...occasionally it will stick to the prop when pulled off and the next prop will rub like heck until the inner hub hits the shaft.

 

[Texasmark]

Re: Noisy Prop

Been thinking about this and I think the engine's number of cylinders can aggrivate the problem.<br /><br />My last engine was a Merc I6, smooth as silk; solid power impulses delivered to the propshaft; ran like a sewing machine, just a honey (just like you guys V6's I'm sure but I never had one......yet).<br /><br />Current engine is 3 cylinder; considerable distance between power pulses.<br /><br />So, during the gap between the power impulses, the water is pushing against the prop, then you get the power impulse and the prop is pushing against the water.<br /><br />So you have this see-saw effect and that is what's doing it to me.<br /><br />So, by giving her a bit more throttle, the impulses are closer together and fast enough to smack the prop before she has had time to backslide and make a bang.<br /><br />My 2c<br /><br />Mark

 

[walleyehed]

Re: Noisy Prop

As long as the engine is turning, there is always a load on the prop in gear except for rapid deceleration.

 

[Texasmark]

Re: Noisy Prop

It's turning but not loaded; hence the essence of a flywheel, but to keep weight down, outboards don't have a lot of mass in the flywheel. So when a cylinder hits, there's increased torque applied which loads the shaft.<br /><br />JD agricultural tractors minimized the problem on their 2 cylinder "Johnny Poppers" with a 500# flywheel.<br /><br />I realize it's a subtle impulse, but an impulse none the less. Why else would this engine do it and my others not, and only do it at idle (650 rpm's)?<br /><br />Mark

 

[walleyehed]

Re: Noisy Prop

Understand your point, Mark, but Factory flywheels are quite heavy and very effective.<br />In fact, most after-market venders offer Light-weight aluminum flywheels for better performance.<br />I can also see a very lean situation at idle causing a hunt-n-peck type Idle that would unload between power strokes, and I've seen this and in every case the prop shaft had no grease.

 

[Texasmark]

Re: Noisy Prop

Kenny, <br /><br />Come back on that? You said "....propshaft had no grease".<br /><br />Would you clarify that please? Are you saying that those that rattled were greaseless between the shaft and the hub and putting grease there stopped it? You aren't talking about lower unit lube are you?<br /><br />My propshaft is essentially greaseless. But with 55 psi of torque on the nut, I can't see the prop rattling on the shaft. Now if the prop were loose and not torqued, I could easily see that rattle. BTDT<br /><br />Buttttttt if you've been there and adding grease solved the problem I am game to pull her off and grease her up.<br />--------<br />I'll totally agree on the lean (which mine is per EPA) and hunt-n-peck. This is what got me going on the 3 cylinder roughness in my previous posts. No doubt in my mind that mine does this. The thermostat, higher ambient temps, and Sea Foam treatments are making it better but it still does it and the unloading you were talking about is what made me think of the impulses jerking the shaft and making the gears rattle.<br /><br />Come back on this.<br /><br />Thanks,<br /><br />Mark

 

[lfb123]

Re: Noisy Prop

Well I adjusted cables. Put in neutral and adjusted cable to line up with hole. This seemed to help some as it was not as loud but still made a tapping or clicking noise. I noted when in gear you could turn the prop about a 1/4 turn either direction before it hit something solid. The stainless prop seems to get planed off a whole lot quicker and runs much better but seems like im drinking more gas too. Maybe im just noticing that more at 3 dollars a gallon lol. Anyway the noise is tolerable now. Iboats also emailed me and gave me contact info at michigan prop. I will call them just to be sure

 

[walleyehed]

Re: Noisy Prop

Mark, Yes, I'm talking grease on the prop shaft...it does 2 things..1, it acts as an anti-sieze, and 2, regardless of how tight the nut is, under load it settles against the splines and you don't want metal to metal. The grease acts as a high pressure seal to minumize the metal to metal which "can" wear the splines over time.

 

[Texasmark]

Re: Noisy Prop

Kenny, I understand what you say and agree. Thought there was more to your comment than that when I first read it.<br />------------------<br />Butch, Go to the Merc forum and look at today's post from me about adjusting linkage. May be something there for you.<br /><br />As far as turning, in F, CCW rotation should meet with stiff resistance....for a standard RT hand prop rotation engine.<br /><br />CW rotation however (in F), is a click, click, click, as the clutch dog (on the prop shaft) slides over the satwooths in the F drive gear.<br /><br />In N you should have no noise, and in R stiff resistance both directions.<br /><br />(resistance is overcome by the crankshaft rotating)<br /><br />Mark

 

[River - Runner]

Re: Noisy Prop

I have a stainless steel prop noise. It's a clattering sound and happens some times at certain speeds, about 1/4 throttle or less. The motor is a 2004 Mercury 3 cylinder 40 HP. 2 stroke (carburetors) with a Mercury Vengeance SS prop...... a very nice motor.<br /><br />I have two different reasons told to me what it was at my marine dealership.<br /><br />The dealership owner said it was the heavy weight of the SS prop causing the lower unit clutch engagement dog disengaging making the clatter and happens under certain conditions, like when slowing down and the lighter weight aluminum props will not cause this to happen. He received a factory bulletin on it and nothing is to be done about it and it is harmless. A month later I mentioned the noise to a mechanic there and he also said that was the reason. He showed me what it was by putting a motor in gear and spinning the prop by hand and said that was the clatter I was hearing.<br /><br />A half year later I asked the dealerships son (he also works there) about the noise, he inquired with another mechanic who said it was exhaust noise and referred me to another employee, because he could best explain it. He said it is the exhaust noise resonating up through the motor because of the SS prop. The prop causes this to happen because it is steel and it is a harmless harmonic noise and it just so happens on these midsize motors because of the characteristics of motor build, design and set up (or something like that). Others asked about the noise. He told them this and they said he was crazy and no way. He then had to prove it to them by going out on the water with their boats and switching between aluminum and SS props. The aluminum props made no noise.<br /><br />I just listened to the reasons and after putting more time on the motor I'm believing it's exhaust noise. It is a clattering noise though and happens at the slower speeds. It never clatters when accelerating and it doesn't happen often so I just accept it, but it is strange.<br /><br />I'm always open for opinions, because I only know what I read or what I am told on this subject.

 

[Texasmark]

Re: Noisy Prop

This thread is getting long, but still contains useful info.<br /><br />River-Runner, seems your (first) Merc mechanic and the one I talked to read the same factory bulletin. <br /><br />I know that the gears are extremely hard and also know that the lower unit oil is specially made to "glue" it'self to the metallic surfaces preventing direct contact. <br /><br />I also know that every time you shift your engine into gear you are slamming these gears together so they get slammed repeatedly in normal operation. Every time you decelerate (slow your boat down) the clutch dog is slipping.....click, click, click.<br /><br />I believe them when they say the prop is doing it and that it is not cause for concern. However.....I still try to minimize it.<br /><br />Now on exhaust noise, I don't know if I buy that. I'm hearing metallic clicking and there is slop in it. Don't know anything in the exhaust loop that can generate a noise like that.....especially when it comes and goes as a function of which prop I have installed. Don't know about your engine, but there is no slop in my powerhead.....well, maybe a couple of thousandts.<br /><br />Mark

 

[stevens]

Re: Noisy Prop

I've experienced this clunk when shifting the engine into gear whenever I've had a propeller without the Mercury Flo Torq II hub. I've tried four of those; the two Turbos and the two Stilettos all clunked, whereas the Black Max, Vengeance and Ballistic did not.<br /><br />I think the flexibility of the hub must play some role here too.

 

[Texasmark]

Re: Noisy Prop

I agree. The tighter the rubber to hub grip, the more apt you are to get clunking.....one would think.<br /><br />Mark

 

[River - Runner]

Re: Noisy Prop

Mark - A little more detail on my SS prop clatter sound. This is for my prop noise, don't know about yours.<br /><br />The motor is a Mercury 40 M and I bought it new. I run it on my small 14' aluminum boat and now have only 20 hours on it (have a tach & hour meter).<br /><br />I was told it's a common occurrence on these midsize motors running a SS prop.<br /><br />That I know of, I cannot make the lower unit clutch dog disengage when the motor is running. Even when I cut the throttle fast and hard at a high boat speed. It only disengages when I stop the motor in gear when the boat is still going forward and then the clatter is very fast sounding.<br /><br />The so called exhaust noise clatter sound is slower and sounds higher up in the motor. It doesn't happen often, but when it does happen it's when I gently slow down at 1/4 throttle or less. I was told it is not metal to metal clatter but just harmless exhaust noise. It does have a metallic sound though.<br /><br />Originally I had a aluminum prop on and it didn't clatter.<br /><br />I agree with you. It's hard to believe what they tell me, that the exhaust can make that noise just because of a steel prop. I still need to put more time on the motor to know, because it doesn't happen often. I had it out yesterday and it didn't do it.<br /><br />Thanks for your thoughts and I'm always open for more.