Perplexed

[dozerII]

2008 Mercruiser 43. 1A316906 I replaced the coupler in this boat last fall, had found all the motor mount bolts were loose and the motor was shifting left to right close to half an inch. I ordered a coupler from Iboats a Sierra replacement. Installation went great and alignment was the smoothest I have done. The boat was used fairly hard for approximatley 50 hours this summer. On the last outing at about 40 mph the coupler went again. I'm kinda at a lose as to what is causing this? The fellow that owns the boat can't give me an accurate wot or idle rpm, he says he can get 5200 at WOT and I asked at idle and he said 1800?? I told him 1800 would explode the lower if he could get it to go in!! He is running a stainless five bladed prop that look real aggressive, I can get the details if it it is required. The gimbal bearing is very smooth but is very easy to swivel in the carrier, not sure if that is important?

Any help would be greatly appreciated.

 

[Alumarine]

Would it be possible to check the alignment now, or is the coupler too far gone for that?

 

[DeepBlue2010]

Is the alignment off again? If so, your engine mounts could be rotten and not supporting the engine anymore. You can take a core sample of them and check

 

[Bt Doctur]

did you replace the rear mounts also?

 

[dozerII]

Would it be possible to check the alignment now, or is the coupler too far gone for that?

Coupler is totally pooched

Is the alignment off again? If so, your engine mounts could be rotten and not supporting the engine anymore. You can take a core sample of them and check

The alignment bar slid right in but the coupler is completley shot, it is an welded aluminum boat with no wood in the stringers.

did you replace the rear mounts also?

No I didn't.

 

[thumpar]

1800 at idle? that is way too high. It should be 650-700 tops. What kind of failure are you having with the coupler? Is it spun or are the splines gone?

 

[Bt Doctur]

the motor cant torque over with solid front mounts so if it is moving the rear mounts are shot.. So this time around replace the rear mounts and you should be fine.

 

[flipbro]

How would you dock aboat with an idle at 1800? Something is off tach wise I would think..

 

[dozerII]

1800 at idle? that is way too high. It should be 650-700 tops. What kind of failure are you having with the coupler? Is it spun or are the splines gone?

Both the this one and the first one were spun, I told him the same on the idle speed, he said he was guessing on it.

the motor cant torque over with solid front mounts so if it is moving the rear mounts are shot.. So this time around replace the rear mounts and you should be fine.

Okay, should this have the spiral wound springs on the rear mounts?

How would you dock aboat with an idle at 1800? Something is off tach wise I would think..

I agree, I have never run the boat myself so can only go by what he is saying. If his tach is off by 1000 rpm and he is only spinning at 4200 not 5200 at wot would this not be an over prop situation.

 

[bruceb58]

When you get your new coupler( I would suggest OEM this time) slide it over the input shaft to make sure it is not worn as well. Shouldn't be but would be a good check.

 

[thumpar]

If it is off by 1000 at idle it will be off by much more at WOT. What are your GPS speed, RPM and prop pitch?

 

[Bt Doctur]

Okay, should this have the spiral wound springs on the rear mounts?
Depends on the type of mount. the old style used the doublewound washer , the newer type use a thin SS washer. The old type were smooth on the bottom and
the newer ones are knurled on the bottom.

 

[dozerII]

When you get your new coupler( I would suggest OEM this time) slide it over the input shaft to make sure it is not worn as well. Shouldn't be but would be a good check.

The splines are a good fit on the last coupler.

If it is off by 1000 at idle it will be off by much more at WOT. What are your GPS speed, RPM and prop pitch?

I'm sorry I don't have that info and either does the owner.

Okay, should this have the spiral wound springs on the rear mounts?
Depends on the type of mount. the old style used the doublewound washer , the newer type use a thin SS washer. The old type were smooth on the bottom and
the newer ones are knurled on the bottom.

I will check the mounts out and get the info off the prop.

Thanks for your help so far everyone.

 

[dozerII]

I have three pictures here one of the coupler one of the mounts which look like new and a strange looking rub mark on the splined shaft in the tapered part in front of the two orings that go in the gimbal bearing.

 

[bruceb58]

That wear mark may have been the input shaft rubbing against the metal of the seal when the coupler let loose. How does the seal look...damaged?

 

[dozerII]

That wear mark may have been the input shaft rubbing against the metal of the seal when the coupler let loose. How does the seal look...damaged?

The seal doesn't look damaged at all. The gimbal bearing is very smooth but seems to swivel in the carrier very easy?

 

[Bondo]

The seal doesn't look damaged at all. The gimbal bearing is very smooth but seems to swivel in the carrier very easy?

Ayuh,.... Sounds like it needs to be pulled, 'n probably replaced,....

If it's wobblin', that explains the seal wear pattern on the shaft,.....

 

[bruceb58]

Yes, shouldn't wobble. Its possible that because it is wobbling means it has some play up and down which would definitely wear your coupler.

 

[dozerII]

Ayuh,.... Sounds like it needs to be pulled, 'n probably replaced,....

If it's wobblin', that explains the seal wear pattern on the shaft,.....

Yes, shouldn't wobble. Its possible that because it is wobbling means it has some play up and down which would definitely wear your coupler.

Thanks guys, so every gimbal bearing I have seen has been very stiff to swivel in the carrier, to the point it will support the alignment bar horizontally that's the way they are supposed to be correct?

 

[Bondo]

Ayuh,.... Correct,.....

That's why the slots go towards the motor, so's the entire bearin', carrier, 'n all is changed every time,.....

Check that the input shaft is true, 'n straight,.....