Screaching sound

bartsbutt

bartsbutt

Member
Joined
24 Jul 2010
Messages
41
Location
ipswich
Visit site
Hi there
I need some advice please.
I have replaced my engine in my yacht and had to change from 2 blade prop to a 3 blade prop. My rope stripper is attached to the p bracket with a space of aproximately 4 inches between prop and stripper, my stripper is 2 bladed and my question is will this affect the operation of the stripper or prop as the blades of the stripper cannot be lined up with blades of the prop.
Also could this set up create a screeching noise from the drive line between 2 certain amounts of engine revs ie 1500 to 2000 revs
Hoping you can help
Rehgards
Graham Simpson
 
Last edited:
What is your prop shaft diameter? It sounds like there is a lot of overhang between the P bracket and the prop. The heavier 3 blade prop might be creating enough shaft deflection at those revs to cause contact with the stern tube. There seem to be a lot of people with issues in this rev range, including myself!
 
pyrojames said:
What is your prop shaft diameter? It sounds like there is a lot of overhang between the P bracket and the prop. The heavier 3 blade prop might be creating enough shaft deflection at those revs to cause contact with the stern tube. There seem to be a lot of people with issues in this rev range, including myself!
Click to expand...
 
Hi pyrojames
My propshaft diameter is 1 inch and whilst motoring along the river with cockpit sole raised I could see no vibration or flexing of the shaft. Once i get over 2000 rpm it stops screeching
 
Is it possible that the noise is caused by harmonics coming from the new propeller. If so, to remedy this, metal has to be removed from the propeller itself. although irritating, the noise will do no harm.
 
I don't think you'll see it flexing or vibrating, it'll just be spinning in the clamp. I had the same thing when we bought our boat, hence my suggestion to check it, I just stuck some tape to the shaft lined up with the clamp top to check if it spun.
 
I had screech when a piece of rope literally welded itself into the cutlass outer ...

Rope Cutters are good - BUT if the rope cuts or gets in the shaft area it does not cover ... then you can get what I had ... I had the Gator rope cutter ...

I know this is not on subject - but later I had terrible noise from under the boat ... so I had it lifted. The Gator where it has a part bolted to the shaft bearing housing was ripped out ... and the half of cutter that was kept aligned by that was loose ...

I removed the bits left behind and the loose half of cutter. The part that was locked to shaft - I kept fitted.
 

Attachments

  • shaftexit.jpg
    shaftexit.jpg
    37.4 KB · Views: 14
They recommend that the stripper:
a) has the same number of cutters as there are prop blades and
b) the stripper is right up against the prop boss
Ambassador Marine
This is so that it catches any rope that has gone round the prop. 4 inches is a big gap for rope to just get wound round the shaft. Sounds as thought your shaft is too long or not fully in the coupling.
 
MoodySabre said:
They recommend that the stripper:
a) has the same number of cutters as there are prop blades and
b) the stripper is right up against the prop boss
Ambassador Marine
This is so that it catches any rope that has gone round the prop. 4 inches is a big gap for rope to just get wound round the shaft. Sounds as thought your shaft is too long or not fully in the coupling.
Click to expand...


Thing is .... OP hasn't actually said which Rope Cutter he has .... or has he ?
 
MoodySabre said:
No, but I assumed it was a Stripper as he referred to a two-bladed stripper rather than a rope "cutter". Anyway, the gap sounds too big.
Click to expand...

Yes, the gap is too big. All scissor-type cutters work in the same way. But I don't think the rope cutter is the source of the noise.
 
Graham376 said:
OP mentions Stripper in his post. As others have said 4" much too far away from prop and shaft does appear to be too long. If the Stripper has been mounted too close in the V block, the screech could be caused by insufficient clearance when the shaft to moves forward under load.
Click to expand...
My stripper is sat next to the prop.

I'd be interested if this is a motor or sailing vessel? If sailing why the move to three blades?

My old two blade prop started turning at 4.8 knots STW and drove me insane, the new folding prop is silent.
 
The move to 3 blade propellorwas because of recommendations of the beta engine supplier, ie beta, I had to go from 2 blade prop to 3 blade and opposite rotation ie rh to lh
It is on a sailer a moody 27
 
You must log in or register to reply here.

Share this page

Top