1990 Force 90HP trim/tilt -engine pops up in reverse

[cleopatraiz]

We've been troubleshooting this issue, replaced the motor, valve and piston and shock "o" rings & relays. Motor lifts fine and stays but it can be pulled by hand from the down to the up position. The result is the engine pops out of the water when you hit reverse. We've tried everything and replaced everything but the main piston. Any ideas why this keeps happening? Any links to a schematic for the entire system...Thanks!

 

[azlakes]

Re: 1990 Force 90HP trim/tilt -engine pops up in reverse

... hiya cleo;

Here is an excerpt from a grey-beard on this subject when rebuilding the pump reservoirs:

On another note. If you engine is over 90HP then be careful prying off the steel caps. If you distort the aluminum then the cap might not be able to stay in place under pressure. After a few months they can pop out and cause anything from complete failure to engine popping up out of water whenever you reverse.

The schematics you seek can change from system to system. But try this thread on for size. See if anything helps your troubles...

http://forums.iboats.com/showthread.php?t=260430

g-luck

 

[Frank Acampora]

Re: 1990 Force 90HP trim/tilt -engine pops up in reverse

If you had the pump apart, did you replace the springs and check valves? There are two spring loaded balls which act as check valves. Some pumps have adjustable screws to adjust the pressure of the balls against the seat. If the ball or spering is missing, OR if the adjusting screw is not tight enough, then the check ball will release pressure when little force is exerted on the engine leg. Thus, it will pop up in reverse.

Careful with the adjusting screw: too tight and the engine will not release when an underwater object is hit.

There are also two check valves for up and one check valve for down in the tilt cylinder piston itself. This allows the engine to release quickly when an object is hit and return down slower to prevent "slamming". If the two up valves are stuck open or worn or broken, this can also cause rising in reverse. However, this is less likely than the check valves in the pump.

 

[cleopatraiz]

Re: 1990 Force 90HP trim/tilt -engine pops up in reverse

Thanks for the ideas, did I mention that the pump and the valves are new? Why would we have an issue inside the valve?

 

[RRitt]

Re: 1990 Force 90HP trim/tilt -engine pops up in reverse

Engine pops up in reverse but does not pop down in forward?
okay, that eliminates tilt piston because it would fail in both directions.

no fluid squirting out of band collar or top seal on tilt ram?
okay that eliminates tilt ram body.


Only thing left is a cut/broken oil tube or a broken valve body. I would give it a 50/50 chance of being fixed if you install a new check valve. That is Mercury part # F17620.

Personally, I doubt that it is something that simple. The low pressure side should never get blown out like that. If it is from debris then the debris came from pump and the question is open as to what part of pump put out such large piece of debris. If it is from the spring rusting through then there are probably other springs in bad shape too. My gut feeling is that new check valve would have 50/50 chance of fixing it for now but it will just break again. My advice would be to buy a new valve body or send yours off for rebuilding.

 

[RRitt]

Re: 1990 Force 90HP trim/tilt -engine pops up in reverse

Thanks for the ideas, did I mention that the pump and the valves are new? Why would we have an issue inside the valve?

oops, missed that.

new pump? If by new you mean used but looked good, then it's still probably a bad pump. Looks mean almost nothing. They break with years of age not hours of use.

If by new you mean factory new or experienced rebuild, then send it back for a warranty exchange. If new/rebuilt then failure is most likely a minor oversight during assembly or a piece of debris. Debris is less likely than oversight but not entirely out of question. Since you have no bleed down at this time then debris came from your old pump. For old pump debris to still be stuck in trim/tilt rams would mean that your old pump had to be really bad-off. So anyway, if pump is under warranty then send it back. Whether debris or oversight it should still be covered.

 

[RRitt]

Re: 1990 Force 90HP trim/tilt -engine pops up in reverse

If you had the pump apart, did you replace the springs and check valves? There are two spring loaded balls which act as check valves. Some pumps have adjustable screws to adjust the pressure of the balls against the seat. If the ball or spering is missing, OR if the adjusting screw is not tight enough, then the check ball will release pressure when little force is exerted on the engine leg. Thus, it will pop up in reverse.

Careful with the adjusting screw: too tight and the engine will not release when an underwater object is hit.

There are also two check valves for up and one check valve for down in the tilt cylinder piston itself. This allows the engine to release quickly when an object is hit and return down slower to prevent "slamming". If the two up valves are stuck open or worn or broken, this can also cause rising in reverse. However, this is less likely than the check valves in the pump.

Force pumps with ball bearing pressure regulation should only have one active tower in the up direction. The down direction should be blank (no channel drilled) and not even have a valve seat, ball valve, or spring. Force pumps with pressure regulated in both directions should have plungers instead of balls. The fluid channels are drilled differently and the two types of valve should not be switched. If you are drilled for ball valves then stick with ball valves. If you are drilled for plungers then stick with plungers.

 

[Frank Acampora]

Re: 1990 Force 90HP trim/tilt -engine pops up in reverse

HMMMM. So then, a pump with ball checks and both towers drilled, tapped, and having set screws and locknuts would be a back yard mechanic modification?

 

[RRitt]

Re: 1990 Force 90HP trim/tilt -engine pops up in reverse

HMMMM. So then, a pump with ball checks and both towers drilled, tapped, and having set screws and locknuts would be a back yard mechanic modification?

most likely from a non-force engine. Volvo AQ290 used adjustable posts in both directions.

The most significant difference is how the forward oil channel is drilled out. On pumps with ball valve the channel is drilled back to gears. On types with post & pin the fluid channel is drilled through to the check valve. The early type (post & pin, <1987) needs to have perfect seal or it will bleed down. The later design (ball, >1988) doesn't need perfect seal because pressure relief is isolated from check valve. There are also some gear differences that relate to type of motor and/or magnets. If you use wrong gear then system can possibly bog out or buck. The best bet is to keep same parts with same assemblies. If you are unsure what casting you have then look underneath valve seat to see how it's drilled. If there is a hole drilled straight through from pressure valve to check valve then you need to use post & pin.