Some questions about 1990 120HP force

[Netjunky]

I have a 1990 120hp force outboard on my bayliner. I have some questions for you guys....

1. I damaged my prop on some moss covered rocks so I need to replace it and have found the identical sized prop/splines on ebay. Do I need anything else or just the prop? It is a mercury prop made by Michigan and is stainless. A flow-tho hub kit perhaps??

2. When on WOT the boat sometimes will bog out. I found that by cleaning the black plug connectors behind the coils for each one the engine will be fine again and run great until it happens again. They seem to have a bad connection there and are arcing. They are a male/female pin connector. I would like to replace these with something compatible. Any ideas? They must be low voltage as they are not thick wires.

3. The tilt is not staying up and slowly drifts back down. The fluid levels are correct. I read somewhere that you have to replace the o-rings in the pump by removing the allen head bolt? There is a ball bearing behind the bolt?

Thanks in advance!

 

[RRitt]

Re: Some questions about 1990 120HP force

I can not speak to items #1 or #2.

Item #3.
Your bleed down is 95% sure to be the check valve with hex fitting. There are two of them one the pump but the one that causes bleed down is the only one you can reach. The other one causes your engine to pop up in reverse when it fails.

I personally think you should have it done. I see way too many pumps where a simple problem turns into a major one. However, the check valves with hex key are the easiest ones to fix. Someone else posted a carberator part that can be used as the needle seat. Just don't split the top half and you should be okay. Even if you can't fix the thing there is no big worry. It is almost impossible to ruin the hex models beyond repair if you don't split the top. The one cautionary note would be not to distort the aluminum when pulling metal cap out of check valve body.

 

[Frank Acampora]

Re: Some questions about 1990 120HP force

Unless you have a dual exhaust lower unit, there is nothing extra to buy. You can use a flo-thru hub prop or a closed hub prop. If you have a dual exhaust lower unit it is preferable to use a flo-thru hub prop. In an emergency, you can also use a closed hub prop but then you are defeating the purpose of the dual exhaust lower unit. Dual exhaust vents exhaust through both the prop hub AND the exhaust snout. In either case, be sure to remove the thrust washer from the inside of the hub of the old prop (if it has stuck there) and slide it back on the prop shaft. If this thrust washer is missing, the prop will slide down the shaft and wear the gearcase until the splines bind and stop it. If it looks in really poor condition, buy a new one and keep it for a spare.

The simplest eway to determine what lower unit you have is to look at it. The dual exhaust lower will have six water pick-up holes in each side running vertically from just above the gearcase torpedo almost in the center of the leg. The single exhaust has four water pick-up slots just behind the prop on each side of the torpedo.

AS for your coil connectors, they are probably corroding due to moisture and bad connections. They handle about 250 volts instead of 12. Take them apart and fill them with dielectric grease available at all auto stores and used on newer car light bulbs. Then reconnect. That MAY solve your problem. I use CDI silicon dielectric grease, part#991-9705. Don't know where to get it though! I got it from an Evinrude repair man for an Evinrude rebuild.--kind of pricey too--15 bucks for a 6-8 oz tube.

 

[jerryjerry05]

Re: Some questions about 1990 120HP force

The trim you mentioned is a 2 stage unit. The first part is trim then after that it is tilt.
Does it leak down from the full up position? Or does it leak all the way down to just the trim position?
If it leaks all the way down then you have a problem in the hyd pump not the trim or tilt.If it only leaks down to the trim then more than likley the tilt cylinder has gone bad.Jerry

 

[RRitt]

Re: Some questions about 1990 120HP force

The trim you mentioned is a 2 stage unit. The first part is trim then after that it is tilt.
Does it leak down from the full up position? Or does it leak all the way down to just the trim position?
If it leaks all the way down then you have a problem in the hyd pump not the trim or tilt.If it only leaks down to the trim then more than likley the tilt cylinder has gone bad.Jerry

I don't think that is true. The 1990 system is not a dual stage pump. The trim and tilt cylinders can backfeed through each other so that if either one fails then neither of them can hold position.

 

[Netjunky]

Re: Some questions about 1990 120HP force

Thanks for all your answers....

I do have the dual exhaust so I will check the hub washers condition...

Diaelectric grease it is...if not I will replace the connectors

I believe the tilt will go down from just after the lock when it is fully in the up position...it goes all the way down. I have noticed in reverse that the motor does start to go up...rebuild time? If so I will just take it all off and rebuild/replace all the o-rings during the winter months....

 

[jerryjerry05]

Re: Some questions about 1990 120HP force

Post a pic of your T+T unit.Jerry

 

[Netjunky]

Re: Some questions about 1990 120HP force

Post a pic of your T+T unit.Jerry

I will take some pictures once I get home...in about 3hours...

 

[Netjunky]

Re: Some questions about 1990 120HP force

Pictures as attached...also does this look like a cowling from a 1990 force? I have not seen one the same as yet...

 

[jerryjerry05]

Re: Some questions about 1990 120HP force

1 picture says a thousand words.That is a 1990. That is a two stage system. 1st stage is trim 2nd stage is tilt up.If it drifts all the way down from the tilt up position the hyd pump is probably bad.If it drifts down to the trim up position the tilt ram is probably defective.
Jerry

 

[RRitt]

Re: Some questions about 1990 120HP force

1 picture says a thousand words.That is a 1990. That is a two stage system. 1st stage is trim 2nd stage is tilt up.If it drifts all the way down from the tilt up position the hyd pump is probably bad.If it drifts down to the trim up position the tilt ram is probably defective.
Jerry

Jerry, you're giving the guy bad advice. The trim piston is about 8x more surface area than tilt and has a fulcrum point about 4x greater. The system is not two stage because of the pump. The mechanical geometry exerts 30x more trim force from the same hydraulic pressure. Once the trim piston is fully extended then all the fluid goes to tilt. Since tilt has smaller surface area it moves more rapidly. Since it has a smaller surface area it needs much more PSI to achieve same force. The system is not two stage by virtue of pump or fluid circuits. It is two stage as a result of geometry. How far it drifts down is meaningless in troubleshooting this system. If you have had success doing so then it is by mere coincidence. The only way to accurately isolate pump versus ram problems is to lift the engine and then cap-off the oil tubes. If it drifts down with the tubes plugged then it is rams. Otherwise you may as well tell people to throw darts at a board.

 

[jerryjerry05]

Re: Some questions about 1990 120HP force

I post from practical experience.I worked on Forces for years at a Bayliner dealer.Was trained to work on them.I have two of them on my boat and have had the same experience with them.
I post from my experience.You post from yours.Jerry

 

[RRitt]

Re: Some questions about 1990 120HP force

back to system at hand ....

From your pictures it looks like the trim motor has been rebuilt. The cable exit would normally point straight back. Because the motor looks rebuilt it is even more likely to be the valve body causing your drift down. Motor and valve body usually go out within a few years of each other. Both fail because the rubber gets old and looses its seal. In valve body it causes bleed down. In motor it causes internal rust.

Because of corrosion, I think you should try to DIY the check valve. The more work that you try to accomplish then the more likely you are to have it explode into a major headache. Even trying to remove the valve body from boat puts you at risk of stripping out hydraulic ports. So I think you should do the absolute minimum and hope for the best.

Get an allen wrench and take out the one forward facing plug. Carefully and gently pull off the steel cap. DO NOT bend it from side to side. If you distort the aluminum then the cap may blow off under pressure. Go ahead and use one of those carberator needle seats. Someone gave the part number in a recent thread and your pump is one of the ones it will fit. It's probably not the right material for the type of pressure needed but it beats heck out of fighting corrosion. I'd rather take the check valve out every spring for 5 years than to take apart a saltwater trim just once.

 

[Netjunky]

Re: Some questions about 1990 120HP force

back to system at hand ....

From your pictures it looks like the trim motor has been rebuilt. The cable exit would normally point straight back. Because the motor looks rebuilt it is even more likely to be the valve body causing your drift down. Motor and valve body usually go out within a few years of each other. Both fail because the rubber gets old and looses its seal. In valve body it causes bleed down. In motor it causes internal rust.

Because of corrosion, I think you should try to DIY the check valve. The more work that you try to accomplish then the more likely you are to have it explode into a major headache. Even trying to remove the valve body from boat puts you at risk of stripping out hydraulic ports. So I think you should do the absolute minimum and hope for the best.

Get an allen wrench and take out the one forward facing plug. Carefully and gently pull off the steel cap. DO NOT bend it from side to side. If you distort the aluminum then the cap may blow off under pressure. Go ahead and use one of those carberator needle seats. Someone gave the part number in a recent thread and your pump is one of the ones it will fit. It's probably not the right material for the type of pressure needed but it beats heck out of fighting corrosion. I'd rather take the check valve out every spring for 5 years than to take apart a saltwater trim just once.

The one good thing I have going for me is that the boat has only been used in fresh water so corrosion will not be as bad. I will search for that needle part number...I will also try and find a breakdown of the pump so I have a schematic....thanks for everyones help!

 

[RRitt]

Re: Some questions about 1990 120HP force

The one good thing I have going for me is that the boat has only been used in fresh water so corrosion will not be as bad. I will search for that needle part number...I will also try and find a breakdown of the pump so I have a schematic....thanks for everyones help!

if there is no corrosion then i think you should take the pump off boat and either send it off or have a hydraulics shop rebuild it. The only valid reason for doing a half-baked job is to avoid the complications of corrosion. If there is no corrosion then I think that you should fix it once and only once ... (fix it right the first time).

 

[Netjunky]

Re: Some questions about 1990 120HP force

Any idea from the picture which tilt/trim version I have bayonet or the other? I want to get a part breakdown of the system from the Mercury part site. I'm also having trouble finding the needle valve part number previously mentioned. The allen key bolt to remove is the one facing out as in the picture? Thank for your help!

The boat has been sitting all winter and now I want to get at it for this season. 2 more months!

 

[RRitt]

Re: Some questions about 1990 120HP force

use the drawings and parts for a 1989 engine. It will use the exact same trim & tilt parts as your engine and avoid any possible confusion or incompatibility.

BTW -
I would bet dollars to donuts that your rams are fine. None of the usual suspects are present in your pictures and it is fairly unusual for rams to go bad without showing some evidence. I'd bet you put a new pump on the system and it goes for at least 5 more years without any problems. At least five, probably more. Next break will be when exterior rust on electric motor creeps past the collar seals.

 

[Netjunky]

Re: Some questions about 1990 120HP force

back to system at hand ....

From your pictures it looks like the trim motor has been rebuilt. The cable exit would normally point straight back. Because the motor looks rebuilt it is even more likely to be the valve body causing your drift down. Motor and valve body usually go out within a few years of each other. Both fail because the rubber gets old and looses its seal. In valve body it causes bleed down. In motor it causes internal rust.

Because of corrosion, I think you should try to DIY the check valve. The more work that you try to accomplish then the more likely you are to have it explode into a major headache. Even trying to remove the valve body from boat puts you at risk of stripping out hydraulic ports. So I think you should do the absolute minimum and hope for the best.

Get an allen wrench and take out the one forward facing plug. Carefully and gently pull off the steel cap. DO NOT bend it from side to side. If you distort the aluminum then the cap may blow off under pressure. Go ahead and use one of those carberator needle seats. Someone gave the part number in a recent thread and your pump is one of the ones it will fit. It's probably not the right material for the type of pressure needed but it beats heck out of fighting corrosion. I'd rather take the check valve out every spring for 5 years than to take apart a saltwater trim just once.

Just to be clear, as I'm going to try this before a rebuild. Is this the allen key piece to carefully remove??

Thanks

 

[Netjunky]

Re: Some questions about 1990 120HP force

Just to be clear, as I'm going to try this before a rebuild. Is this the allen key piece to carefully remove??

Thanks

I found this thread with a Check valve needle seal part number, is this what I will need?

http://forums.iboats.com/showthread.php?t=282435&highlight=needle+seat&page=2

Thanks.

 

[Netjunky]

Re: Some questions about 1990 120HP force

Update: Finally got around to replacing the part under the hex headed bolt. I bought the kit from a local lawn repair shop, it was in stock. Tiny o-ring about 3mm wide. Took the hex head bolt off and inside the head was a spring with a needle with a little point the comes out the front on the housing on the bolt. Took it apart by carefully pulling it apart and found one tiny piece of o-ring, so otherwise it was gone. Replaced it, reassembled & added oil. Tested and left it up 1 inch off the trailering bar. It stayed that way overnight! Works great now! Unfortunately I got used to using the leaking system to automatically lower my motor after droping it in the water then parking the car