View Full Version : Vibration after sharp turn???

11-10-2004, 08:19 PM
Yesterday I took my 86 Prostar 190 Power Slot to Castaic Lake in So California (no one around a little on the windy side). We decided to see how tightly she could turn (considering the dealer had done some VERY tight turn when we test drove the boat last month)!! We soon stop when a vibration started at around 2500-3000 RPM. The first thing I thought was we had bent the shaft or messed up the prop doing tight turns???

Well after limping back to the ramp and removing her from the water, I couldn’t see any damage on the prop or shaft. I did notice the rudder was very loose.

So today I removed the rear seat and deck to gain access to the rudder linkages, and found the adjustment nut very loose!! I have tightened up on this nut and retighten the locking screw and then greased the assembly.

My question is how much play should there be in the rudder?? And would a lose rudder cause vibration?? Or do you think the prop shaft may be damaged from the tight turns?? Is there a way of setting up a test gauge to see if the shaft is bent??

:confused: :confused: :confused: :confused:

11-10-2004, 08:31 PM
A loose rudder will definitely cause vibration. Think of it as a loose front end on a car. You should have very little play, if you mean that by grabbing the rudder you're checking to see how much bigger the hole is than the rudder shaft. As long as it's lubed and seals well, there doesn't need to be any sloppiness for it to work properly.

I haven't seen a propshaft damaged by tight turns, but that doesn't mean it's impossible. If you have access to a dial indicator, you can check the shaft for wobble. If you hold the indicator steady and have someone else turn the shaft at the coupler, you'll get what is probably the most accurate reading. Less than .005" total is allowable if you measure at the mid point between the cutlass bearing and the strut. If you don't see any there but do see a variance after the strut, it needs to be addressed.

12-02-2004, 11:48 PM
These type of turns can throw your entire drivetrain out of adjustment. They are accurate to .003" i believe is the spec. If you engine mounts are loose you could have slid your engine over a bit and that would cause a wicked vibration.

Those types of turns are also very hard on yoru boat. If you have ever seen boats that have cracking in the gelcoat around edges and in corners of seat bases, you can probably bet it has been used hard and abused. Think of your gelcoat like mud. If you dip your hand in mud, then bring it out and let it dry, then flex your hand, the mud will crack. Granted, gelcoat is much stronger than the mud, but this is what happens. It is a good way to devalue your boat pretty quick.

east tx skier
12-03-2004, 10:20 AM
We had some vibration issues that turned out to be shaft packing. Sounds like other sources are more likely for you, but if all else fails, check that.

12-03-2004, 12:59 PM
I agree with MCPS205.

I had an '86 Skier with the Powerslot, Blue Rainbow stripes and everything. Old Blue looked identical to your boat.

That boat had the best hull for doing bat-turns. But, like stated above, it puts a lot of strain on the boat, and can very easily cause the engine to slide.

It may not be a bad idea to unbolt the shaft coupler from the transmission and separate the two a small amount. This will show you how close to being in line the engine and shaft really are. Then, reallign everything to .001 of a gap (I think the gap is correct). The manual explains this process. It's not difficult, just a little time consuming. Bad allignment can wear out strut bearings prematurely.

Also, FYI, my rudder had a little play in it too. I took it apart because I was told it should be solid (by just another owner). I tightened and lubed everything, put it back together and it was still the same. I was later told by a former dealer that that rudder was supposed to move slightly? I didn't care though. It wasn't broken, so I left my hands off after that. It only made noise when I turned the rudder all the way, and I was at idle speed.

Propeller: Propeller blades can be bent closer to the center of the hub and it is almost non-detectible without placing the propeller on a balance. A good propeller shop can put your prop on a balance in 30 seconds and tell you if one of the blades is off. It only needs a very small bend, or different angle out of the hub to cause vibration.

I'm sure it's a great boat. Try the easy stuff first. I miss Old Blue.

12-03-2004, 01:00 PM
I doubt there is any way the prop shaft is bent. I've hit rocks & not bent the shaft (thanks to the sacrifice of the brass prop!). But it sounds like there was enough slop that it knocked the engine/trans alignment out of wack. The alignment is measured with a feeler guage at the front of the propshaft where it connects at the coupler behind the trans. Adjustment is made at the engine & trans mounts. I don't recall the spec but I'm sure your dealer will.

12-06-2004, 09:24 AM
I actually just hit my prop on a boat ramp yesterday trying to manuever to pick my girlfriend up. (The water was too cold for her to walk out too far :mad: ) Anyway, I ran it after that, and the engine ran fine, but I noticed a vibration. Now this is the first time I have used the boat since I test drove it with the dealer, it's a 91 PS190. It didn't have this vibration then. When I got out and checked the prop, obviously I pretty much destroyed it, one blade was completely bent and another was not quite as bad. I'm wondering if a severely bent prop could be the sole cause of the vibration. I was only at idle speed when I hit, and by eye the shaft looks fine. I just ordered a new 4-blade replacement and I have my fingers crossed that the vibration goes away, any thoughts?

12-06-2004, 09:42 AM
Propeller: Propeller blades can be bent closer to the center of the hub and it is almost non-detectible without placing the propeller on a balance. A good propeller shop can put your prop on a balance in 30 seconds and tell you if one of the blades is off. It only needs a very small bend, or different angle out of the hub to cause vibration.

I'm wondering what a prop shop can do with a very tiny bend on the tip?

I folded over the tip of one of the blades approx. 1 to 1 1/2 inches wide, and maybe 1/2 deep from the very tip edge.

I thought about straightening it out myself, but the brass looks pretty intimidating since I don't know what it can withstand

insert bonehead move here ---> :cry:

12-06-2004, 09:53 AM
jsonova99- a minor ding in a prop can cause a bad vibration so yes, a major one can definitely be the sole cause. Your prop hit something that didn't move and the weaker object lost the battle. Take it in and have them determine whether it can be fixed. Running the boat with a bent prop can damage the shaft, strut and throw the alignment off. There's a lot of stress at the end and you can only tell if there's major deflection by eye.

milkmania- if the tip has a minor bend, they can fix it. They can replace up to about 1/3 of a blade, so just the tip shouldn't be a problem. It can't be fixed cold. They have to heat it to get it to bend without breaking.

east tx skier
12-06-2004, 10:34 AM
jsonova99, even if you've got a new 4 blade on its way, send the old prop to OJ and get it refurbed (I'm assuming it's an oj). I put a 45 degree bend on my father-in-law's 4 blade this past summer (not to mention what I did to the shaft). OJ refurbed it perfectly. The boat now runs more smoothly than it did before the accident. Total cost was right at about $105 with shipping. It's good to have a spare prop.

12-06-2004, 10:54 AM
EastTX, thanks for the info, sounds encouraging, I will definitely send the old on out. They'll probably laugh when they see it. My fingers are crossed that this fixes the problem.

12-20-2004, 10:40 AM
In response to my previous post, I installed a new Ambush 4-blade prop, and there isn't the slightest hint of vibration in the boat at any speed, dodged a bullet there!! :D I'm looking into getting my old one fixed now as a spare.