Newbie trim pump, 888 questions.

[Markh762]

Sorry all, wicked newbie to sterndrives but not to boats. I've ordered a manual but haven't received it yet and I'm curious about a couple of things. <br /><br />I've got a 1976 starcraft with a mercruiser 888 (302 ford) setup. It's missing the trim pump. When I look in the engine bay I can only see 2 hydraulic lines hanging around but when I look up the part it always says something about 4 lines and I can't figure out if I'm missing something. Any thoughts?<br /><br />Okay next one. There's this thing that the hydraulic lines go through that also hook up to a couple of the the shift cables, is this a saftey valve of some sort that only allows trim to operate when in gear?<br /><br />Last one for now and this is a very general question. I've got quite a few wires, sensors etc that have been unhooked, wires cut etc. Most have to do with the outdrive or in that area, Is this a norm for older boats? <br /><br />Thanks, Mark

 

[qaztwo]

Re: Newbie trim pump, 888 questions.

On the shift plate, back of engine, reverse lock valve. two lines run from the pump, up circuit and return, which when ran backwards is the down ciruit and return. 4 lines might be to trim cylinders.

 

[Ralph 123]

Re: Newbie trim pump, 888 questions.

Just to expand a little on qaztwo's answer.<br /><br />Let's start at your trim rams (the things that connect from your gimbal ring to the back of your drive outside the boat. That has 4 lines. 2 to each ram. They connect under the gimbal housing to what I call a manifold. 2 lines on each side.<br /><br />If you remove the 2 nuts and pull that manifold down, you'll see those 4 lines connect to 2 lines. One of those lines run directly to the trim pump and the other runs to the shift plate on the back of your engine. <br /><br />The valve on the shift plate that the hydraulic lines connect to is call a reverse lockout valve (RLO). Its purpose is to prevent the drive from rising up (also called out) when you are in reverse (The force of the prop running backward can cause your drive to be pulled up by itself due to the force) the RLO valve prevents that from happening. <br /><br />The other line connected to the RLO valve runs to the trim pump. So, the trim pump only has 2 lines connected - one to the RLO and the other to the manifold.<br /><br />Newer boats do not have a shift plate on the back of the engine and the RLO valve is actually built into the "new" style trim pumps (oildyne style).<br /><br />Your original trim pump was most likely a "Prestolite" style.<br /><br />If you buy a newer style pump (oildyne), you don't have to connect to the RLO valve. You connect both lines directly from the pump to the manifold. If you buy an old style prestolite, you'll need to connect to your RLO valve and possibly adjust it so it works properly.<br /><br />Now, as for the shift plate, you'll see one of the mechanical shift cables runs from the plate to your shifter (also called remote control). The other cable runs from the plate down to your drive.<br /><br />The arm on the port side of the plate that both cables connect to, is the arm on the top of the RLO valve which is what "activates" it when you're in reverse.<br /><br />I hope this helped and makes sense.

 

[Markh762]

Re: Newbie trim pump, 888 questions.

qaztwo, Ralph. Thanks very much for the answers. I can almost be dangerous with that info The less confusion when working on things the better. I was able to get an old style 2 line merc pump assembly off ebay so hopefully it'll fix me up. <br /><br />Thanks again,<br /><br />Mark