1988 100hp Merc power tilt & trim falls on its own

H

Hessian7

Recruit
Joined
Apr 15, 2009
Messages
3
Hi All,

New to forum and there is an amazing amount of information here - fantastic.

I have a 1988 100hp Merc that everything related to the power tilt and trim works fine but in both tilt and trim mode the engine will drop slowly over time to the lowest position. When the boat is under way and the system is under a load the trim will drop faster than if the boat is going slow or stopped so the load placed on the pistons seems to dictate how fast it falls. The sytem is not leaking fluid, its full of fluid and properly bled. I'm constantly re-trimming the engine up for optimal running angle. This is the 3 ram system with one tilt cylinder and two smaller trim pistons.

Below is a link to the unit in question. I'm looking for advice on either how to troubleshoot it or what parts might need to be replaced. Thanks.

http://www.boats.net/parts/search/M...nts(Three Ram Power Trim Design I)/parts.html
 
S

sschefer

Rear Admiral
Joined
Nov 13, 2008
Messages
4,530
Re: 1988 100hp Merc power tilt & trim falls on its own

Hessian7 said:
Hi All,

New to forum and there is an amazing amount of information here - fantastic.

I have a 1988 100hp Merc that everything related to the power tilt and trim works fine but in both tilt and trim mode the engine will drop slowly over time to the lowest position. When the boat is under way and the system is under a load the trim will drop faster than if the boat is going slow or stopped so the load placed on the pistons seems to dictate how fast it falls. The sytem is not leaking fluid, its full of fluid and properly bled. I'm constantly re-trimming the engine up for optimal running angle. This is the 3 ram system with one tilt cylinder and two smaller trim pistons.

Below is a link to the unit in question. I'm looking for advice on either how to troubleshoot it or what parts might need to be replaced. Thanks.

http://www.boats.net/parts/search/M...nts(Three Ram Power Trim Design I)/parts.html
Click to expand...

Sounds like it's time to replace the seals. It's time consuming but not that hard. The system is designed so that if the engine is above the trim level and with normal propping you reach rpms of 2000-2500 the relief circuit in the pump will activate and the engine will return to the max trim height. Your description describes the normal trim ram(s) failing which usually indicates it time for a rebuild.
 
H

Hessian7

Recruit
Joined
Apr 15, 2009
Messages
3
Re: 1988 100hp Merc power tilt & trim falls on its own

Thanks for the reply.

Based on the link in my original post could you pick out the item number or numbers that would include the seals you believe may be the culprit. I'm guessing you would be referring to item # 16 - The O-Ring kit but I want to make sure.

Thanks again for your input.
 
S

sschefer

Rear Admiral
Joined
Nov 13, 2008
Messages
4,530
Re: 1988 100hp Merc power tilt & trim falls on its own

Hessian7 said:
Thanks for the reply.

Based on the link in my original post could you pick out the item number or numbers that would include the seals you believe may be the culprit. I'm guessing you would be referring to item # 16 - The O-Ring kit but I want to make sure.

Thanks again for your input.
Click to expand...

There is never a single culprit seal. The minute you tear it down all seals get replaced no matter what condition they are in. If you go to your local/nearby Merc dealer with the serial number for your engine he can look up and order the exact kit you need. That's the very best way to save yourself time. While your there, order a service and parts manual. You will never regret it.
 
H

Hessian7

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Joined
Apr 15, 2009
Messages
3
Re: 1988 100hp Merc power tilt & trim falls on its own

I already have the manual. I will hit up the local dealer for the kit he feels is my best shot at solving the problem. Thanks again for your help sschefer.
 
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