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BF50 tilts up when running boat in reverse

M

mitchbuck

Contributing Member
My 50hp Honda has been running well this season thanks to help on this forum! Anyways, one item remaining that I need to fix is that whenever I put the engine into reverse and give it some throttle, the engine begins tilting out of the water. When backing up I have to keeping pressing the trim down button on the throttle otherwise the engine will raise completely out of the water. I have twins Honda 50s on my 21ft seacat and the other engine doesn't do this. There must be something cross wired. Any ideas?
 
I'd guess the hydraulic ram on the tilt cylinder has an internal leak. Does that same engine lose it's trim while accelerating?
 
Yes, check the fluid level. Also, the manual valve may be slightly loose. Make sure that it is screwed down tight.
 
The hydraulic fluid level checks out and I followed the procedure in the Shop manual. How do I got about checking the manual valve and check valve? Looks the manual valve has a C-clip and then it just unscrews? Looks like the check valve asssembly just unscrews?
 
Yes, the manual valve is the one with the circlip located closest to the transom. The cap with the oversized slot just next to the manual valve holds the spool valve in the valve body.

Check the manual valve by using an appropriate slot screwdriver and tighten by turning to the right.

The spool valve might be what some are calling a check valve. If you decide to unscrew the cap and check the spool valve for being stuck, be very careful that the valve doesn't surprise you by "jumping" out of it's bore. You can remove it and use ATF to clean it and the bore but be aware that the spool valve assembly is made up of several pieces and you don't want to get them out of order when going back together.

WARNING: Just a spec of dirt on the spool valve or it's bore can cause te valve to jam. Work on these parts should be done in the cleanest of circumstances and out of even a very light breeze.
 
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Thanks for the input jgmo! I checked the tightness and everything is snug as it should be. I am going to try to tackle these valves this weekend.
 
These units can be resealed and you can even rebuild the motor with parts available on boats.net

But if you're not a hydraulics tech, take pictures as you go to keep things under control.

Good luck.
 
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