Stainless props causing vibration on 25hp

I have a 25 hp 4 stroke Mercury, 2007. When I replaced the 3 blade aluminum prop with a 4 blade stainless, I received a lot of vibration. Went back to the aluminum...smooth as silk. Thinking it may be the 4 blades causing the vibes I tried a 3 blade stainless...same thing. A lot of vibes but not as much as the 4 blade. Both stainless props were Solas. Could it be that the weight of a stainless prop on this engine is too much. And that is what is causing the vibrations? Or is it possibly Solas. Thanks for your input. Getting ready to buy a 3 blade Solas aluminum....I guess, or should I stick with a Mercury Prop

Re: Stainless props causing vibration on 25hp

I think we touched on this on another post has it gotten worse or just bugging you?
I would say that is unusual.Typically a 4 blade is smoother.
Just a stab in the dark if the prop shaft was slightly out of whack,bent or had
a little wobble or side play.The heavier prop might amplify it.You could take the prop off and rig an indicator next to the shaft and rotate it by hand,see if there is any runout.
Put the prop on and do the same thing with it.
I don't recall any Soplas ss vibration problems.
I wouldn't hesitate to get a 4 blade al Solas.

Re: Stainless props causing vibration on 25hp

I talked to Mercury, they dont think its a SS or weight problem, they think it is a Solas problem, more than likely. Unfortunately there prop apparently is not good for my engine. The Mercury is a ton smoother. Im sticking with the Merc props, at least they want vibrate my rods out of the boat.

Re: Stainless props causing vibration on 25hp

I don't think you have a Solas problem. Swapping props from 4SS to 3SS with the same results pretty much proves that. 25 hp to me translates to 2 cylinders, alternate firing and being 4 stroke, one bang per cylinder every other rev. Your bangs are farther apart than mine so your problem would be more evident.

I have a 90 hp 3 cyl 2 stroke. I can run smooth as silk on my lowest pitch SS, or low pitch alum which are also the lightest weight. When I put the highest pitch on, it weighs a lot more than the others and obviously requires more engine hp to turn it being of higher pitch.

With only 3 bangs (plug firings) per rpm, there is enough "space" between the bangs for the prop to slow down and get boosted with the next bang. This makes for a lot of vibration at idle. Once you get the rpm's up it's smooth as silk as the bangs are close enough together to reoccur before the prop has had time to slow down (much).

You didn't mention at what rpm your are experiencing your problem but with that engine I'd say it's normal if only at the lower speeds.

Mark

Re: Stainless props causing vibration on 25hp

The motor is a 3 cylinder 4 stroke,so maybe there is a power pulse condition.
Might even be an internal balance issue that is amplified by the rotation of the heavier
stainless prop. In his other post he did say it smoothed out as rpm increased.

Re: Stainless props causing vibration on 25hp

steelespike said:

The motor is a 3 cylinder 4 stroke,so maybe there is a power pulse condition.
Might even be an internal balance issue that is amplified by the rotation of the heavier
stainless prop. In his other post he did say it smoothed out as rpm increased.

Click to expand...

Sorry for the misinformation. I just went to the Merc www and realized as you said it is a 3 cyl. Even at that he is hitting half as often as I am and his opportunity for a similar problem is magnified 2:1.

Mark

Re: Stainless props causing vibration on 25hp

I agree with your thought process whether a 2 cyl.2 stroke or a 2 or 3 cyl 4 stroke.
there is some sort of rotational dynamic going on.I would think a 3 cyl 4 stroke could have some balance issues.

Re: Stainless props causing vibration on 25hp

All I know men is that the 3 blade aluminum merc prop is smooth from 0 to 6000 rpm. The SS Solas cut the water great with greater holeshot and speed. Just couldnt handle the vibration. Not only was it annoying on the quiet 4 stroke I was also in fear of potential damage to bearings and or lower unit. This engine is running great right now. Just in the summer, when the air thickens up, I lose a lot of RPMs...which may be an engine issue uinstead of a prop issue. I go from 6000 down to 5200 loaded. Then the hole shot and speed suffer significantly.

Re: Stainless props causing vibration on 25hp

Are you saying warm weather slows you more with a load if so how many rpm less than cool weather.Does it change rpm on a light load?

Re: Stainless props causing vibration on 25hp

tblack111 said:

Just in the summer, when the air thickens up, I lose a lot of RPMs...which may be an engine issue uinstead of a prop issue. I go from 6000 down to 5200 loaded. Then the hole shot and speed suffer significantly.

Click to expand...

I'm not a meterologist but cool weather brings air that is more dense down here and speed increases normally with that more dense air.....course if you are in the summer and it's 99.9% humidity that may work just as well. You are dropping a lot of rpm's loaded. Maybe you are on the edge of your torque performance curve with your loaded condition.

What happens during hot weather when unloaded?

On props, Turning Point brand Hustler (sell them here on iboats) has some high performance alum that you might want to try. The have everything that SS props have except thin blades which has an effect on performance over the SS brother.

Mark

Re: Stainless props causing vibration on 25hp

I replaced my Merc Laser II with a Solas ss 4 blade and have no vibration on my 115 optimax. don't think it's the prop. does your prop have a flow torq hub? the flow torq's will sometimes vibrate where the flowtorq II will not.

Re: Stainless props causing vibration on 25hp

Proof positive. IF POSSIBLE.

Have another person try your 3 props.

Honestly.......Solas could have run off a bad batch of 3 & 4 blades. Car companies run off thousands of rejects all the time.

Why can not Solas have a bad run ??

Solas might tell you your Aluminum is the one out of balance. If someone tries a stunt like that. MEMORIZE HIS VOICE !!! Keep dialing untill you get a different person at Solas.