2005 75 hp mercury optimax trim and tilt problem

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Sep 7, 2012
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I was recently out and I put my trim up to accelerate and while accelerating past 6 mph the motor goes back down and wont go back up until I get off the throttle and go below 6 mph. The trim and tilt seems to work fine on the trailer. Any idea on the cause?
 

Iceman66

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image_211912.jpg Sounds like there is some internal leak , maybe a valve that not seated properly or a seal inside .

Are you sure that the manual release screw is screwed all the way in ? Could also be a bad seal(o-ring) here.
Number 9 (down to the right in picture):
 
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hi thanks for your reply...I checked the fill screw and even purged the fluid...I put the motor all the way up...filled the fluid...lowered it down...raised it up again...filled the fluid...repeated this 5 times. all worked fine. went out again and the same scenario...motor went down at acceleration. is there a rebuild kit for this? also the pic u sent me is awesome but it is too small to view the schematic. any other repair videos out there or resources to find a fix? yhamks
 
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also there are no leaks with fluid anywhere here. I cant get this situation to repeat out of the water. I mean I can lean on the motor at tilt up and it will lift me off the ground and not go down. cold here in PA right now. hope to get a fix before ice over.
 
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also should I have a stop thru the holes on the motor to keep it from going down too far? I'm not sure if there is a pin that goes thru both holes on the motor. I did see this on Yamaha motors. There are holes there so there must be a part. any idea of a part description and or a part no. to purchase it?
 

Iceman66

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If there is an internal leak,there are no fluid leaking out from trim/tilt unit.

No stop bolt at transom on these engines when equipped with tilt/trim.

Sure you have checked the manual release screw? You will reach it through a hole down at the starboard transom.


Here is a link to a better schematic:
http://www.crowleymarine.com/mercury.../11211_280.cfm
 
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just checked the manual release screw it did turn tighter just a bit. should I take it all the way out and check it? prob will lose fluid if I take it all the way out right? btw that's a pricey screw around 50 bucks. looks like 3 o rings on there. think its a good idea to replace those?
 

Iceman66

Petty Officer 2nd Class
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Jun 30, 2008
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Sorry fore late answer, have been out of "town".

Could be one of the O-rings at the manual release screw or some other parts (nr 5,10 or 15 area at the schematic),
or it can cust be dirt at a valve/seat inside.
Guess you have to disassemble it to find out, and yes, there will be fluid spill when doing that.

Recomend some mechanic knowledge and experience and maybe a manual before starting a complete
disassemble of the unit.
 
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Sep 7, 2012
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thanks a bunch. what is the best manual? any idea where I can purchase one? checked ebay look like the Seloc or Clymer manual is avail. cant find the shop manual for this motor.
 
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Sep 7, 2012
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Thanks for your link. I did download the factory manual. Also I did replace the tilt trim assembly with a new one. The symptoms are exactly the same as the old assembly. When out on the water at throttle up to get up on plane the motor just drops right down. I can go about 5 miles per hour and the motor stays up on increase speeds the motor drops right down. There is a trim sender on this motor its a 2006 75 elpto optimax serial no. 1b244674. Could the sender be bad? are there relays or something electrical to check? Hard to believe a brand new oem mercury trim assembly would be faulty and produce the exact same symptom as my old trim assembly. Help?
 
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