2000 90TJRY Tilt & Trim Drifts Down

[Dusty-Pants]

I have a 2000 90 hp 2 stoke jet drive with power tilt and trim. I have owned this engine for four seasons and have had this problem from day one.

When boat is under power the trim will drift down and I need to constantly retrim for optimim speed. When fishing I tilt engine completely up so that waves do not slosh into the jet intake. The tilt will drift down over time and I have to retilt then engage the locking lever to hold up.

Every once in a while, the unit will function normally and the T & T will hold the engine where I desire but this is quite unusal.

Since all three cylinders were acting the same I thought the culprit valve would be one that is common to all three, so I focused on the manual override valve. I have played with the manual override valve many times and that does not seem to have any effect on the problem.

Several weeks ago I removed the T&T unit to replace the override valve "O" rings but the new ones were the wrong size. The old ones did not looks bad and I wanted to go fishing so I put it back together with the existing parts and as no surprise it functioned like it normally does.

Now with the boat and engine in storage and the T & T unit on my workbench I would like to permanently solve this problem.

Any suggestions on where to start or where to get a good service manual?

[TownsendsFJR1300]

Here ya go:

YAMAHA MANUAL STORE

[Dusty-Pants]

TownsendsFJR1300

Thanks for the link. Do you happen to know if the T & T section is very detailed?

I have a Clymer service manual that gives general instructions for unit removal but nothing for unit disassembly. After reading some of the horror threads on this site I am getting a little nervous about ripping this thing apart.

I got prices from a couple local boat shops and they want around $900 to rebuild it. The price for the all the seals, seats, and O rings is about $150. I figure I can tinker a long time over the winter for that difference.

[robert graham]

My 1999 C90 Yamaha leaks down some, but more slowly than what you describe for yours....Hope you have some good luck fixing yours...my guess is that some of those valves are just leaking down, but the repair sounds like beyond my capabilities....again, good luck and keep us posted with your results!

[TownsendsFJR1300]

Thanks for the link. Do you happen to know if the T & T section is very detailed?

I have a Clymer service manual that gives general instructions for unit removal but nothing for unit disassembly. After reading some of the horror threads on this site I am getting a little nervous about ripping this thing apart.

I got prices from a couple local boat shops and they want around $900 to rebuild it. The price for the all the seals, seats, and O rings is about $150. I figure I can tinker a long time over the winter for that difference.

My Yamaha shop manual is VERY DETAILED. It is written for the shop mechanic so should you not have ANY experience, it may be a bit more difficult to use.

***Also, what's very helpful, in the upper right of this page, there's a "Purchase Yamaha Parts" in RED. If you key up on that, find your engine, specific section, it show's parts in the unit, in general how its assembled (no spec's).

[rodbolt17]

look for faulty,
up main valve
up relief valve
manual release valve
trim piston orings
free piston

[Dusty-Pants]

Thanks for the reply everyone!!

TownsendsFJR1300, that sounds like the manual I need and thanks for the parts list tip.

Rodbolt17, thanks for the tips. Question on the valves....I am presuming they are like other hydraulic valves that are a metallic body with seals of some sort on them. Could the bodies go bad and need replaced or just the seals on them need replaced?

I will be ordering the spanner wrenches and Yamaha service manual in the next few days. Should have everything on hand to start this adventure after I get the jet drive bearing, seals, and water pump back together.

Have a Merry Christmas and I will post my progress.

Again, thanks everyone.... this is a great site!!

[robert graham]

Good luck on your tilt and trim repair adventure, and when you're done you'll most likely be an expert on this complex unit....might be able to share your experience with some of us other guys!....merry Christmas!!!

[Dusty-Pants]

Update on this project: Lower unit is compete and ready to reinstall.

T & T, I have received Yamaha service manual and made the spanner wrenches for the cylinder end caps. Broke loose the tilt cap, having strength issues with the trim wrench. Hope the redesign is successful but those caps are very tight. For now the entire unit is still together.

Reviewed the manual and I have a question about the tilt piston assembly, how do I replace the seal in the end cap? In the manual it appears to be trapped by the clevis and piston. There are no specifications for piston torque onto the ram but there appears to be spanner wrench holes in the piston. How difficult is it to remove the piston in order to replace the seal? The seal is somewhat dried out so probably should be repaced. Any thoughts?

[TownsendsFJR1300]

Reviewed the manual and I have a question about the tilt piston assembly, how do I replace the seal in the end cap? In the manual it appears to be trapped by the clevis and piston. There are no specifications for piston torque onto the ram but there appears to be spanner wrench holes in the piston. How difficult is it to remove the piston in order to replace the seal? The seal is somewhat dried out so probably should be repaced. Any thoughts?

Are you referring to the seals on part #20?:

2000 90TJRY Yamaha Outboard POWER TRIM TILT ASSY Diagram and Parts

I've never had one apart but looking at the parts fisch but it appears as you state, the piston needs to be removed.

I suspect that piston is threaded on the shaft. Especially since it has holes for a spanner.. Likely clamping the head in a vise (with aluminum pads) should protect the upper end of the ram.

Check for loctite (likely not used), and with no spec's, its likely "good and tight"(pay attention when pulling apart). It really has no where to go...

[Dusty-Pants]

Yes, item 20. In the manual it looks like the rod and piston are threaded. This is going to be exciting, sure would hate to make scrap out of my item 20 $$$$$.

I wonder how tight the tilt ram and piston have to be. Seems like the free piston would help prevent ram piston from unscrewing while operating. Hmm, I wonder what is the purpose of the free piston?

Hope to try the redesigned trim spanner wrench this weekend. I am getting anxious to get this unit ripped apart.

[Dusty-Pants]

Update

I have everything loosened and most of the valve o-rings and seats replaced. Have to fininsh the shuttle valve and the trim cylinders then fill with oil.

I did have a little trouble with the down relief valve assembly....the seat came out before I saw which way it was oriented. Unfortunately the service manual is not help much in this area. I have attached a picture of the way I think it goes into the housing with the spring on top. Could someone confirm if this is correct or if the seat is backwards?

I was wondering if the trim spring retaining pan head screws (item 62) may be replaced with socket head screws?

Finally (for now), I understand I should fill all cavities with fluid as I go. After that is there any secret to filling the reservior or anything else I should do before actuating to ensure I don't blow-up the unit?

[TownsendsFJR1300]

No idea, someone will have to chime in.

[TownsendsFJR1300]

He's WAY BEYOND adding just fluid and needs information re re-installing a valve/spring to complete the repair

[Dusty-Pants]

Thanks for the replies, please keep them coming.

So far I have not seen anything that looks out of ordinary in any of the valves and pistons seats or seals and housing bores. Although, I am not very knowledgeable about how much resistance you should feel with the O-ring fit.

The only thing I saw that may explain the drift down is when I pulled out the manual override valve rear seat a piece of something that was gunky/slimy about 5/8" long and maybe .010" diameter came along with the seat. When I previously pulled that valve I didn't dig that deep so I don't think I introduced the gunk, although who knows.