Does engine alignment ever change as motor mounts age - 2004 ProStar

[swbca]

Been trying to figure out a whining noise coming from the transmission at 1000 rpm. The sound has a pulsing that may coincide with the rpm of the rear shaft . . The shaft appears to a a slight amount of runout a few inches behind the coupling. Runout can happen because of a bent shaft or engine alignment correct ? Nothing has ever happened to bend the shaft.

[MattP]

Yes alignment can change. Just had our 2011 CC that was repowered in 2016? that now has 2,000 hours realigned.

[BraceMaker]

They "sag" most all boats if they are aligned new the whole engine will be gradually settle lower compared to the shaft.

 

Best thing to do is to pull the shaft seal forwards a few inches, disconnect the shaft and check your engine alignment first. Then re-check the run out.

[DW]

@swbca - what happens when you run the engine @1k RPM with the shaft disconnected? Engine alignment can change over time for a few reasons.

[swbca]

@DW You must have a great mind, that's the first thing I was going to try to see if the stress caused by engine misalignment on the rear bearing of the transmission was causing the noise.

[Jerry44]

It will definitely cause a noise in the strut bearing. I just had my 2017 Prostar with 213 hours aligned. No idea why it was out so bad and so soon.

 

One thing you can check. Look under the boat where the shaft comes out of the boat. It should be close to center of the hole. Before the alignment, mine was at the bottom of the hole and it is centered now.

[eyepeeler]

When you align it try to get it better than the .003 tolerance...get it down to a gnat's a$$.

[S1Pitts]

Question? Are you aligning on the trailer or floating on the water. I found that there is a difference so I always align in the water.

[GaryJanzig]

I always have my engine alignment checked every 400 hours when I take it in for a tune-up since the boat was new. Don't have the guts to attempt it myself.

[swbca]

OK Experts; let me verify alignment methodology. On my 1975 Nautique and 86 ProStar I performed engine alignment with a feeler guage. With the 4 bolts loosened on the shaft coupling, I would adjust motor mounts to get the same same space in the coupling top, bottom, left, right. Then confirm after turning the shaft/coupling to other arbitrary positions.

 

On my 86 ProStar I did a major change in 1987 when they switched to a new power-slot strut that was an inch longer than the first 1986 strut which caused hull vibration because the larger prop was too close to the hull. That required moving the engine quite a bit. The results were good.

 

When I checked my current ProStar last week (in the water) it was extremely close but not perfect. Someone said get within .003" Not sure if .003 is equal to a nat's-ass or just another expression to emphasize getting it as good as possible.

 

Another observation about my current ProStar. With the coupling disconnected, the vertical range of motion of engine-end of the shaft is about an inch, and when connected, the shaft is tight to the top of that range. ie the engine is higher than the strut's centered shaft trajectory. What about that ?

[Jody_Seal]

@swbca

lower the engine overall if the shaft is not in the middle of the insert.

it will align.

my son gets them to .0015. I am always astonished when he does an alignment.

having clean coupler faces are crucial to a good alignment. wet the strut cutlass with either wd 40 or dish soap. I like to take all the bolts completely out as well as slide the packing and hose to expose the log for center. one can get erroneous feeler gauge readings if you can't spin the shaft coupler free from the transmission coupler. especially if someone in front of you has used a hammer in the process or just plain machining differences.

 

 

[DW]

@swbca - Yes, it is important align with the shaft centered vertically as JS noted. If yours has been running in a forced position, there may be some cutlass bearing wear that would require attention. Are they the vesconite or rubber ones? Rubber probably has more misalignment allowance that the hard vesconite ones.

 

@Jody_Seal - makes parents proud when the 'kids' master tasks and then keep improving past the parents. :D

[BraceMaker]

,003" is literally the feeler gauge thickness that fits inside the flange when maligned. If you bring the flanges together they should line up really nicely on center with no offset alignment with the shaft centered in the log, then if you take a feeler gauge and go around the flange at no point should a feeler gauge thicker than .003" slip in. As @Jody_Seal is saying if you take a thinner feeler gauge and a .0015 won't slip in then your alignment is essentially twice as good.

 

If the shaft when decoupled runs off at an angle through the shaft log with the shaft seal slipped forward (really hard to do on a powerslot MC) then you either have a bent strut OR a poorly installed shaft log - I did have a boat that was beautifully aligned but the shaft log basically was rubbing and I took a grinder and took the log out of the hull then feathered out the glass and reset the log so it was aligned to the shaft. I only did this after taking a bunch of measurements and verifying that the shaft was running very true to the hull, the log and engine were very nice but the log was just cooked in the hull.

 

 

 

[fu_man]

Ron Tanis makes great videos on this kind of stuff:

 

 

[fu_man]

@S1Pitts Am I missing something? You have to remove the shaft seal to verify it is centered. How are you doing this on the water? Or are you starting with the presumption it is already centered in the shaft log? Trying to imagine how water/trailer would affect it regardless.

[BraceMaker]

He's noting the effect of a probably poorly fitting trailer. I've honestly never separated mine in the water to check as I won't separate the coupling unless I remove the prop, too easy to nail the prop into the rudder.

[S1Pitts]

@fu_man Remove the packing assembly from the shaft. Grease the shaft then I center the shaft with clay and then use a condom to seal the shaft to the log.....zip ties to keep condom in place. Allowed 1/2 rotation in either direction.

I admit it was a lot of work for very little adjustment compared to what I had on the trailer but it got rid of the slight shimmy in my ass when I was driving. OCD?

[DW]

@S1Pitts - well if you really want to get it right, how about doing it dynamically:-) You know the wetted surface and hull forces change at speed... I've tried but am just not fast enough to undo the coupler nuts at 3500 RPM:-) I have noticed the weight of the coupler on the shaft does allow it to droop when removed, so that has to be compensated for when getting true shaft angle / couple position accurate.

[Jody_Seal]

@DW that's some funny shite right there.

 

I once asked a surgeon why he gets paid to do pretty much the same thing I do with engines and transmissions. he replied try rebuilding them while they are running...

[swbca]

Procedure variation . . . rather than using a .003 or thinner feeler gauge, I always used an arbitrary thicker gauge and made sure the degree of friction between the gauge and couplers is a trace-equal amount all the way around after pushing the rear coupling forward with the gauge in its first position. There is enough friction between the shaft, strut and other components to hold the rear coupler in the original position while inserting the gauge top,bottom,left,right. If there is a trace amount friction that feels equal all the way around it should be good, though there is no known tolerance value.

[S1Pitts]

@DW FUNNY!

I have contemplated using a grid coupler which would just complicate the whole thing. KISS prevails.