'96 Regal Rush XP-120hp Jet Power Loss

Need a little help, I'm new to the forum and I am hoping you guys can give me some pointers. I have come to posses (temporarily) a '96 Model Regal Rush XP with a inboard 120HP Mercury Jet Drive Motor. I am new to jet drive boats as well. this is the first I have used. I am, however, familiar with engines and outboard prop motors somewhat.

I'll try to describe the problem as best I can, The boat has been sitting for about a month. I went through everything as best I could prior to putting it in the water. The boat still had about 2-4 gallons of fuel in it. I filled it the remainder (about 8 Gal). The owner told me that it has been giving him a problem getting up on step and pulling a skier is extremely difficult. I found out today exactly what he meant.

The motor itself appears to be working fine, it maintains RPM, however, going to full throttle it has no power whatsoever, from a dead stop in the water to full throttle it will not get up on plane, at all. At full throttle the engine rev's as if it is cavitating and mearly sucking air. At about 60-70% throttle it will get up to speed and plane off and reach an acceptable cruising speed. Upon making a left or right turn (right turns more than left) it loses power again as if it is cavitating. And on a full 180 degree turn it bogs down terribbly and will take several hundred yards to get up to speed again.

Now what I have already done and plan to do. I checked the output and intake side of the jet with it out of the water, all the impellers look fine, there are no obstructions on the underside grate and nothing on the output side to disrupt flow. At first it seemed as if it were riding heavy in the water, as if perhaps rainwater or something had accumulated in the hull somewhere, but, I can hear no sloshing if I shake the boat on the trailer (Its a very light boat). So I ruled that out. I really don't think it is an engine issue, but tommorrow I plan on putting a can of Sea Foam and running it with premium unleaded just in case. I figure it can't hurt it anyhow.

Having said all that, after riding in it for about 45 minutes, I did finally get it to run and catch up at 100% throttle, but once I backed off, it did the same thing again, and would not step up again. After running it for about an hour and a half it used roughly a half a tank of fuel (which seemed a bit rich to me as well) and about a quart and a half to 2 quarts of oil. It was smoking, but not excessively and no more than I thought normal.

Now, I know this thing is really nothing more than a Wave Runner on steroids. it's a 4 seater and only 14' long, with a 120 Merc behind the thing it should jump out of the water like a beast and scream. I am thinking there's a problem with the jet drive, hopefully someone can give me some tips of something to check. What would cause it to loose water like this? Or perhaps a slipping impeller shaft? I am open for ANY ideas! Please feel free to email me direct at kf4kmr@wildblue.net with any ideas or suggestions on what to try. Thanks!

 

Can you elaborate on the 2 quarts of oil?

This is a 2 stroke correct?

Fuel mix is usually 100-1 ------ 2 quarts is approx 80 gallons of fuel!!!!!

So you have seperate tank for oil? This is oil injection?

 

Yes, this is an oil injected engine, and it may not have been 2 quarts, I really don't know exactly how much the oil tank holds,it looked to be roughly a gallon or so, and it used about half the tank.\

That help?

 

Now that I think about it, I think the oil tank holds 1/2 gallon, and it used half of that, so really more like around 1 quart of oil was used. Sorry about that, I took a second look at the tank and realized it was smaller than I first thought.

 

Well even half of that is way out.

The engine is not going to like chomping through that amount of oil.

If it is 100 -1 oil mix for your engine it is easy to see that your oil consumption is out.

Some serious figures of fuel and oil consumed would help.

An engine is fairly forgiving with oil mix but that much could be your problem.

 

I filled the tank up this morning and it took 10 1/2 gallons of fuel,Which is what I used out of the full tank, Added a bottle of Sta-bil and a can of Sea Foam to it. I could be off a little on the amount of oil used. It wasn't smoking much and the little bit of smoke I saw was white/blue. If it was burning too rich on oil it would be smoking much more, correct?

After sleeping on it last night I thought about the impeller shaft perhaps being broken,cracked,bent,loose, whatever. I got under it today and put my fingers through the intake grid and tried to move the shaft, it was good and tight. This is when I noticed the intake plate, held on by 8 bolts, only had 4 in it. and was hanging down about 1/2-3/4", I went to town and bought some new bolts and run them in it pulling everything up tight. found 1 bolt sheared off, which I am going to try to pull and replace in just a moment. I don't know that that would create enough drag to cash this much loss of power. But I know it needed to be fixed. Also, I am not sure of the correct terminolgy for it, but the cover which opens when going forward and closes when reversing (in front of the water output on the back of the boat, when in the full throttle position was still covering the top of the water output by about 1/2". I adjusted the cable fastener so that it would stay open when in full throttle and out of the way.

Going to take it out shortly and see if any of this helped. Will report this evening.
I am still open to any ideas anyone has.

 

The reverse deflector being stuck slightly down may have had something to do with the boat's strange behaviour; so would a loose intake grate- I'd give the jet pump a full inspection as soon as you get the chance, make sure everything's there, tight and in its proper place.
I would hope that the engine's oil injector unit knows what's best for it, but it sounds like there may be a problem there too. Your engine is just the powerhead off a Merc 120 outboard bolted to a 90-degree gear; it shouldn't smoke any more than the comparable outboard does (which is little to none, once warmed up). Excessive smoking would suggest excess oil, which could be fouling the plugs or otherwise causing trouble.
The way you describe it bogging down makes me suspect something wasn't set up right in the first place and now it's sucking air into the pump in turns....

 

Well, here is my results, About 2 hours on the lake today, My repairs seem to have fixed the problem. The boat will now set-up much better after replacing the missing bolts and adjusting the shield on the back.
However, It still seems to me like it should have more power than it does, it takes 30+ seconds for it to get fast enough to get set-up and on hard corners it seems to bog in pretty deep. But, overall I am much happier with how it is working today.
I'll probably keep toying with it to see what other improvements I can make. If anyone has more suggestions I am definately all ears.

Thanks!
MB

 

The intake grill issues will have a big effect, and you seem to have fixed that. The tolerance of the impeller to the wear ring (sleeve surrounding the impeller) is crucial to jet performance. If you do not have a stainless wear ring, it is likely that the gap between the impeller outside diameter, and the wear ring is too great, causing cavitation, as you describe. You can get a stainless wear ring fitted to the smaller hp sportjets, and the tighter the tolerance, the better (much) the performance. Single digits in thou is what you are looking for, for ultimate response.

 

Have a search around on Riverjet There are guys that have fitted UHMW wear rings on Mercury Sportjets to very tight tolerances, and getting fantastic performance.

 

I was just poking around on the net and came accross this little bit about the Rush.

"An E-ticket ride to be sure. Regal hit on a neat combination of sporty, hip looks with one of the better-performing compact jetboats out there. What I really liked about the Rush was its spinability, but even more so its quick recovery from a spin. The pump seems to stay loaded with water and ready to blast away from wild maneuvers that would cause many other boats to cavitate and lose thrust. "

Which leads me even more to believe that I may actually need that wear sleeve looked at. I am most definately NOT a boat mechanic, so if I continue to use this thing, I'll probably just take it to one of the shops here locally and have them tear into it and see what it could be.
It may just be me, but even after my "easy repairs" it still seems to be lacking the bottom end power I think a 120 should have. It could just be me, We are going to take it back out this afternoon and try pulling a skier (200+ lbs.) and see how it handles getting him up on top.

Thanks for the comments guys, either way I am going to suggest to the guy who actually owns the boat, that he get the impeller sleeve checked out if nothing else.

He want's to get $3000 for the boat as it is. However, it has been kept outside, with no cover, the seats need to be recovered and the hull needs new gel-coat as well as a few other minor issues, including a service for the engine and obviously the drive needs to be looked over too. I may offer him $1500 for it, but that would be top.

 

Similar Problem

I just bought a 1995 Regal Rush xp w/ sport jet 120, I also can not get up on plain very well. I takes about 1min to get up on plain and that is if I send a 200 pound person to the front of the boat. After a long time I can get the boat to about 40 - 42mph but I just can't imagine this boat is supposed to be that sluggish out of the hole. Does your boat get up on plain at all? since mine does get up on plain after a long time does anyone have any ideas what could be causing this? and if it is the ride plate gasket how hard of a job is that to replace and does anyone have a link or photos to walk someone through this procedure???

 

After buying a 94 regal rush 90 hp merc I also am suffering from the lack of speed ect after doing alot of research on the problem it seems the regal rush suffers from this problem after many hours of reading their seems to be 2 fixes for this lack of power ect 1. ride plate gasket and 2.wear ring if any one has any further info would greatly apreciate your input..

 

UHMW wear rings

I have put in a least 300 UHMW wear rings into all types of sportjet pumps and also I build uhmw wear rings for outboard jet pumps and the performance is second to none as the tolerance is around 5 thou and there is less slippage and there fore more thrust out the hole is awesome and in most cases 2 MPHR faster on top end on out board jet pumps the tolerance is Zero as the impeller touches the wear ring so if you guys are looking for more performance from your sportjets e-mail at norkar@telus.net or reply to this forum


Let'er buck

 

don't know the boat but here's my immediate reaction...

...sounds like life on a jet pushing a lot of boat.

general maintenance is important and good suggestions here, which i would do anyway, but for those whose craft is in good working order try lightening the load and remove as much drag as possible. remove the bimini, coolers, ice, water, and passangers. half-tank and a calm day, then test your take-offs. that's what 120hp will do with a jet on a boat like this.

jets are not notorious for their take-off they are fast and agile on the turns, quick to recover with skags. but 120 hp isn't much heat for a boat this size, not from what i can glean from the web anyway.

footnote -- among the volumes of advice you might get do not, repeat do not attempt to heat-up just this engine alone without a professoinal mechanic familiar with the drive train.