96 Mercury 120hp sportjet JET DRIVE PROBLEMS, please help!

[120xr]

Ive been trying to get my boat running WELL for 6 months now, and its been 1 battle after another. The latest is a little out of my understanding so I am asking for some advice and or help. My boat, 96 Sea Ray SeaRayder 120xr sportjet, turned on just fine and idled out perfectly, after giving it some gas, upwards to 4,200rpm it would loose pressure and over rev (never planing out). I observed under the hull and where the ride plate sits, Ive noticed that the gasket/seal is off on the side closest to the bow. After reading some forums, I know that some people have had problems with powerloss over ride plates. Im wondering if I blew, or damaged mine? Please help

 

[calledinsick]

Re: 96 Mercury 120hp sportjet JET DRIVE PROBLEMS, please help!

If there is a large chunk or big piece missing, I'd replace it. If it's a small piece you may try some silicone caulk/sealant as long as the ride plate is flush with the bottom of the boat.

It's not hard to replace, I use Dawns dishsoap/water in a misty bottle and spray all surfaces well to help slide it together.

 

[120xr]

Re: 96 Mercury 120hp sportjet JET DRIVE PROBLEMS, please help!

Thanks for the quick response, I will try to get that seal back in. I don't know what the ride plate is suppose to look like at flush. The seal doesn't have missing peices it just came off, maybe when starting it on shallow waters. Do you thunk that could be the reason, or should I expect damage to the ride plate/ wear ring?. Thanks again, new here and new to boating

 

[Crater]

Re: 96 Mercury 120hp sportjet JET DRIVE PROBLEMS, please help!

I used a small bead of silicone on the surface that the seal sits on in the can. Also cause the seal is thick, the bolts wouldn't line back up very well so I used a quick clamp(wood working bar clamp) on the ride plate and the stator (i think) just look for someway to push the ride plate forward to get the bolts to line up. By using the clamp it gave me a very good seal on the front on the ride plate. FYI don't use too much silicone cause it will actually hold the seal down and you won't get a good seal. (found this out the hard way). I also ran a small bead around the hull and ride plate seal after it was installed. Let it sit overnight to dry or you'll end up with a real mess (also found this out the hard way.) Cleaning silicone off is a pain so do it right the first time and have patience. Your problem sound just like it's cavitating (sucking air through the pump) at high rpms, it can be problemmatic so try and get a good seal. Also if you motor is over reving you have other issues also, it should have a rev limiter so stop that from happening. Make sure that there is nothing stuck in the pump ie a rock, it would divert water (as would a ride plate that is hanging down or badly dented up) and if it comes loose and goes through the impeller then you got big dollar repairs. Something eles to check is the position of the reverse gate, make sure at WOT it is fully clear of the nozzel. Something I noticed is that a little extra weight makes a noticable differance on getting to plane, so lighten up any extra stuff ya have on board at least until you get in to plane in a reasonable amount of time.