Power trim shudder - 90HP 4-stroke Merc

[Georooney]

I didn't find any info in the FAQs, and a search of 'power trim' returns 500 hits. I won't live long enough to read all of them, so am hoping someone can help me out here.

On the first trip out this year, I discovered that the power trim won't trim down while the boat is on plane. There's a shudder that you can feel throughout the boat. If I slow the boat down, the motor trims down just fine like it's supposed to.

I checked the fluid level after the boat was back on the trailer; it was fine (to the bottom of the fill hole, as per the manual).

I trailer the boat, and at the boat ramp I didn't personally let the motor down off the manual tilt lock lever, and I'm wondering if the guy who did accidently tried to lower the motor against the lock and damaged something? Could that have blown an o-ring or something? One would hope that Mercury would have the power tilt protected against such things. And anyway, isn't that what happens each time you trim the motor all the way down until it stops?

Any info, suggestions, similar experiences are greatly appreciated. Thanks.

 

[Georooney]

Re: Power trim shudder - 90HP 4-stroke Merc

Any takers? Or is this an unusual situation?

From the level of expertise I see on this forum, I was sure somebody would have a suggestion. :|

 

[spestka]

Re: Power trim shudder - 90HP 4-stroke Merc

I have a very similar problem with my 50HP Merc. Did you ever get this resolved? I'm trying to find a solution myself. Thanks!

 

[Georooney]

Re: Power trim shudder - 90HP 4-stroke Merc

Nope. One guy on another forum suggested that the grease in the tilt tube might be caked up, causing the tilt to be sticky. Makes sense, as the trim motor has a harder job of pushing the leg down against the flow of water while on plane than it would lifting the leg up, so stickiness would be more noticable then.

I plan to flush the grease through the tilt tube this weekend. If that improves things, I'll post the result.

 

[MCotherman]

Re: Power trim shudder - 90HP 4-stroke Merc

Air in the system or leaking seal... Air will make it jump. Just rebuilt my trim system. 16 years old and seals hard as rocks.

 

[RRitt]

Re: Power trim shudder - 90HP 4-stroke Merc

too many possible engines and systems. if you want an answer then you're going to need to say exactly which trim system you have. post a pic, a link, or a clear description of your trim system.

 

[Georooney]

Re: Power trim shudder - 90HP 4-stroke Merc

Sorry, I wasn't aware there were many different systems to trim an outboard motor, specifically a 90 HP 4-stroke Mercury, as originally stated. I figured that anybody who was familiar with that motor already knew the system, and if they weren't they couldn't offer any advice anyway, unless they had experienced similar problems.

too many possible engines and systems. if you want an answer then you're going to need to say exactly which trim system you have. post a pic, a link, or a clear description of your trim system.

 

[RRitt]

Re: Power trim shudder - 90HP 4-stroke Merc

I have personally repaired five different systems that would fit a 90HP four stroke. Since that is the extent of your description then here is the extent of my answer. Something to do with one of your psitons is probably worn out.