1998 mariner motor mounts

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bfan781

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Hello,
I have a quick question for somebody to help me out with. I was told by a merc mechanic that at some point I need to have the motor mounts replaced and that is causing the engine to vibrate/ shake. When running you can see it moving slightly. Not sure exactly how to explain it but the engine isnt still. Is that the sign of a broken mount? Wanted to make sure he wasnt pulling my leg. Is there a good way to tell if it is the lower or upper mounts? Or both.
Can the boat be used safely until I have the time/funds to address if it is the mounts. Engine runs good otherwise.

thanks
 
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Chris1956

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Re: 1998 mariner motor mounts

He is hanging on your ankle. The only time to replace them is if they break, and that almost never happens, unless you hit something at high speed. More likely the motor is slightly out of tune. Pull the powerhead straight back. if it moves 3/8" inch or more, something is wrong with the mounts. Same for the gearcase. Motor mounts are rubber so 1/8" of movement is normal.

get a new mechanic.
 
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bfan781

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Re: 1998 mariner motor mounts

Hi Chris,

When the cowling is off and I pull back on the powerhead the whole motor (entire unit) lifts up. Does that confirm there is an issue with the motor mounts?

Is there a way to determine if it is the upper or lower? From what I see the uppers are a lot harder because the powerhead needs to be removed. What about the lowers? Can it be determined ahead of time what mounts are broken?
 
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bfan781

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Re: 1998 mariner motor mounts

I don't have it on me right now. i can post it when I get home tonight. It is a 1998 115HP 2 stroke 2+2 setup. So should the whole unit not lift when I pull up on the powerhead? Does that point to or rule out either the upper or lower? i will post the s/n tonight
 
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carholme

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Re: 1998 mariner motor mounts

What exactly do you mean "pull up on the powerhead"? That is pretty heavy to be lifting vertically when installed.

If it is indeed a 1998 s/n, here is a link to the parts list:

100/115/125 H.P. 80 JET (4 CYLINDER) - Mercury, Mercruiser, Force, etc. Parts Lookup

See the lower mounts, item 12 under DRIVE SHAFT HOUSING.

See the upper mounts, item 4 under EXHAUST PLATE.

If you provide the s/n and PM me with an email address, I should have the service manual for it and will send it to you.

Gerry
 
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bfan781

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Re: 1998 mariner motor mounts

Hi Gerry,
Yes its definitely a 1998 and I will check the S/N later. I guess pull up is the wrong description, I tried what Chris mentioned above. I stood in the boat and with cowl off, I pulled the motor back towards me by the powerhead and the motor lifted back/up, like it was being power tilted. Is that the correct test for the motor mounts? Does it lead to suspect either the upper or lower? thanks for your help !
 
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bfan781

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Re: 1998 mariner motor mounts

Hi,
That is a great part list. I see now where they are located. I just need to confirm if there is a way to actually tell if they are broken and whether or not it is the upper or lower ones. Will I be able to tell by looking at the lower ones if I take that plate off?
thanks
 
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gbrowne9

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Re: 1998 mariner motor mounts

i have an older version of the same engine and the movement is probably from the swivel bracket bushings. my lower bushing is gone so the engine moves back and fourth about 2 inches.i havn,t decided whether to take it all apart or not.
 
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bfan781

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Re: 1998 mariner motor mounts

Ok so now that I know where to look, I do see a good amount of play at the lower mounts. I will take a video and post to get some feedback to see of actually broken because I don't want to replace if I don't have too.

I took off one side and see the nut and screw fairly rusted. The rubber mount appears intact but ripped up at the bottom. Are these a pain to replace? What does the screw on the engine side go through? Or does it just kind sit there and the plate holds it in. I'll post the video and tell me what u think about the mounts.
 
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bfan781

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Re: 1998 mariner motor mounts

I did take those parts off but it hard to see the condition of them because i am not sure what I am looking for. The bolt is rusty and the rubber mount appears intact but ripped up at the bottom.

Has anyone ever replaced these?
 
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carholme

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Re: 1998 mariner motor mounts

Are you operating in a lot of saltwater? There must be some terrible corrosion in there or the rubbers in the mounts are completely shot for that much movement. If it were my engine, it would be coming apart now to be repaired. It is a big job.

Item 16 under SWIVEL BRACKET AND STEERING ARM is where the mounts bolts pass through and the swivel bracket has to be removed to change the mounts. You will have to lift the powerhead to get to the upper mount so it is a complete disassembly.

Gerry
 
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bfan781

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Re: 1998 mariner motor mounts

Thanks for the reply. Yes, the boat has always been used in saltwater. So because of the play there, that proves that there is an issue with the lower mounts correct?

So (just trying to put this together in my head) The nut is on the swivel bracket end, how does the mount bolt secure to the engine side? Why does the swivel bracket have to be removed? The nut is easily accessible, just don't see how the bolt goes through gets connect and how it all goes together. I assume that to remove that bracket that is why the upper bolts have to be removed and power head removed.
 
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carholme

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Re: 1998 mariner motor mounts

Yes, there is something wrong with the lower mounts!.

If you look at the link in post #12, the rubber mount fits into a recess in the leg and is clamped when the clamp, item 18 is bolted in place. Bolt, item 13 is too long to be removed when everything is assembled. You should be able to see this when you have the cover and the clamp removed from the leg. The swivel bracket has to be removed as the bolt that passes through the mount also goes through the yoke and when you remove the nut on the end of the bolt, you cannot remove the bolt as it does not have the room to slide forward out through the rubber mount, therefore the only way you can get it out is by removing the swivel bracket and steering arm. When it is being removed, the yoke slides off the two mount bolts and the mounts can be removed.

As I said, this is a big job but only you can decide if you should tackle it or not.

If you don't feel that the swivel bracket has to be removed, just undo the two nuts that pass through the yoke and try and remove the bolts.


Gerry
 
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Chris1956

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Re: 1998 mariner motor mounts

Just to be clear. The motor mounts do not go bad very often, if you don't hit anything. The motor mounts are bad if the midsection can move away from the tripleclamp by more than 1/4" or so. To do the test, the motor must be locked down in the operating position. Now, standing behind the prop, pull back on the gearcase. If the space between the midsection and the yoke on the steering rod, gets larger by 1/4" or more, the mounts are bad.
 
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bfan781

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Re: 1998 mariner motor mounts

Thanks Gerry,
I wasn't doubting you, I just need things explained to fully visualize it. I see what you mean now. I was also curious if it was a definite the powerhead and upper mounts needed to be removed to replace the lower ones. That influences whether or not I am going to tackle it.


Hey Chris,

I will redo the test just to make sure it was done correctly. It may not have been completely locked down when I did it originally. I have a video above, not sure if you saw it.
So just to make sure I do it correctly, I'll put the motor completely down and stand facing the prop and pull back on the lower unit while watching the space around the bolts.

I don't go around hitting bottom (LOL) , but there may have been a time I slowly bumped the bottom in low waters..

Chris,
Is it a guarantee that I need to loosen the upper mounts to remove the lower bolts?
 
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bfan781

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Re: 1998 mariner motor mounts

Re did the test. Lower mounts definitely shot. Now I just need to determine if I should try to tackle the job. Of the power head didnt need to be removed I would say definitely but it seems like it is a lot more work.

Can the boat be used with busted mounts? Safely?
 
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Chris1956

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Re: 1998 mariner motor mounts

You may be able to get the mounts replaced w/o pulling the powerhead. See if you can loosen the nuts behind the yoke. If you can get those lose and all the covers off, the mounts may have enough sideways movement to be replaced. If you can get the bolts loose, the whole job should take less than 1/2 hour.
 
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