Tilt and trim

[e.wallace]

Have a 91 200merc and engine tries to climb out of water if I over rev the engine in reverse. any suggestions why? Tilt and trim operates perfectly up and down and holds in place at idle or evern WOT in forward but climbs in reverse. Any suggestions?<br /><br />Told you I would be back! =)

 

[jimmy@wm]

Re: Tilt and trim

I'm not too familiar with the components of the tilt and trim but it sounds like maybe you have a cylinder leaking or a relief in the pump may be bypassing. I know a little about hydraulics and this would be my guess without looking at a print. I'll look at one and see if I can be more specific.<br /><br />Jimmy

 

[dilligafda]

Re: Tilt and trim

"Have a 91 200merc and engine tries to climb out of water if I over rev the engine in reverse. any suggestions why? Tilt and trim operates perfectly up and down and holds in place at idle or evern WOT in forward but climbs in reverse. Any suggestions?"<br /><br />The trim is operating as designed. The unit will climb up in reverse just like it will jump up if you hit something underwater.

 

[KCLOST]

Re: Tilt and trim

It sounds like the pilot check valves in the pump... I've never replaced or serviced them before but you should be able to get the parts pretty cheap...

 

[mulliganmagic]

Re: Tilt and trim

My grandfather's 1988 35hp Mercury use to do the same exact thing, however it didn't even have power tilt trim. This could possibly be due to some device on the transom bracket that isn't holding the engine down well enough.

 

[arboatdr]

Re: Tilt and trim

The problem is in the hydr. pump. First you must decide if it is a square or round pump motor. The pumps will not interchange. Second, get ready to spend several hundred dollars on a non-servicable pump. You will need the engine serial number to order the part from your local merc dealer. The pump can be removed by tilting the motor up and removing the transom bracket from the pump side. Be sure to support the engine firmly with a hoist while tilted. Loosen the manual release valve and remove the pump/motor assy. You will need to look for debris in the pump housing and replace th o-ring on the manual release valve as well. This takes an experienced tech around 3 hours to do if no problems arise. Get ready to spend a day doing this. Be extremly careful since the trim system is under hi pressure. I would take it to a dealer to fix it if i were you or just use it as it is. Good luck!!

 

[dilligafda]

Re: Tilt and trim

I will state my point again and add some definition.<br /><br /> The trim is operating as designed. The unit will climb up in reverse just like it will jump up if you hit something underwater. <br /><br />The trim system is not meant to hold the engine down. Actually the opposite is true, the trim functions to hold the unit up/out away from the transom against the force of the prop. It is also designed so that if an under water object is struck, it will take the shock and return to it's original position. <br /><br />Using that knowlege, when you put the engine in reverse, you are exerting the same force as striking an object. The more you rev the engine (put pressure against the trim system) the more it will want to climb out of the water. All of this is outlined in the Mercury service manual. <br /><br />Now, if it does come out under low throttle, you may have an issue with the trim ram or valve body. It can be repaired, but the job is not for the faint of heart. It requires supporting the motor and trim system removal and a good knowlege of trim/hydraulic systems. If you have access to a service manual, check out the trim section and it will show you exactly how to do this, but if it were me, I would get it to my nearest dealer.<br /><br />Good luck!

 

[arboatdr]

Re: Tilt and trim

Under normal boating conditions this trim should not come up in reverse. If a hot foot or a control box that exceeds 1/3 throttle in reverse is used it can come up. An underwater impact at 20+ mph is not the same as powering up in reverse. There is a problem with your unit, however, it may be something tou can live with. I do think if you want it repaired you should take it to a dealer and let them take a look at it. We use v6 mercs to tow docks with and at times we have to power it in reverse. They do not come up under power.

 

[DHPMARINE]

Re: Tilt and trim

If I over rev the engine is in the first line of the request.Hope someone doesn't over rev the engine too often. DHP

 

[arboatdr]

Re: Tilt and trim

i stand corrected!!