OMC Turbojet 115 HP - Please help!

Here's the current situation. I got a '96 Boston Whaler with the OMC 115 HP TurboJet. I had someone work over the motor, check compression (which is good) and do the carbs then the guy who was helping quit...so it falls into my lap to finish up. I've got it running but....the pump (?) sounds pretty clunky meaning it's noisy and there's some excess vibration. Local mechanics won't get involved (though they would work on it if it was the Mercury engine!). They're telling me that there are all kinds of special tools for the OMC and they're not even going to touch it.

Can anybody tell me how difficult it would be to get to the sealed bearing for the pump? Check the impellor? Any other helpful information about this Jet Boat? I still don't have my service manual yet for it so if anyone has a scematic diagram of the gear box, lower end pump assembly that would help me "see" whats involved. I can do most reasonable maintenance but I don't want to get too far over my head and so far there's not many people who work on these in my area (NNJ). If it just pulling the pump housing at the back of the boat, I can do that to cet to the main seal and bearing. Pulling a bearing may not be so far out of my realm either. However, if I have to go further in and/or pull the engine out....I just don't have the cherry picker to do it.

PS: I know that there are only two kinds of people on the forum having read the post from severel years back...those that like Jet Boats and those that don't. Please respond with helpful comments only as I'm pretty much committed to getting this boat on the water and having fun with it as the boat hull upholstry, and motor itself is in really good shape.

Re: OMC Turbojet 115 HP - Please help!

They make a clunking noisy out of the water. Change the gear oil, use the good stuff.

Re: OMC Turbojet 115 HP - Please help!

Thanks for that. You know I asked a mechanic standing by when I started it about the gear oil and they told me that wouldn't be the problem. I have absolutely no experience with this motor so if you could...explain where in the heck I find the gear oil fill / drain plugs and I'll do it now. Next on my list is to check the imprellor to see it the clunking is where it might be hitting the housing due to corrosion. Thanks for the help.

Re: OMC Turbojet 115 HP - Please help!

Next on your list should be to get an OEM service manual! You mentioned you don't have it "yet". Have you ordered it? Do it now. Outboardbooks.com or ebay if the local BRP/OMC dealer can't get it for you.

Re: OMC Turbojet 115 HP - Please help!

Drain plug bottom of gearcase, under the boat hull. Fill plug Starboard side, rear of engine.

I used HI-VIS premium.

Re: OMC Turbojet 115 HP - Please help!

Thanks. Got an eyeball on the fill plug and the drain plug looks like its under a flat cover forward of the intake screen. Those screws are corroded pretty bad and I'll have to get Hex sockets to get some leverage. Any other ideas on how to get them to back out except muscle? Then if I strip the hex socket on those flat head SS screws I guess I'm looking at drilling them out right? Yeah, pretty sure that's how it goes.

I may just avoid it and fill the gearcase from above and not drain the case right now as I'm not prepared to drill out the SS screw at the moment.

I removed the Impeller housing and it is scraping a bit which is most likely the reason for the engine vibration. I'll grind down the edges to keep it free and clear plus make sure I order a backup to have on hand. The leading edges of the fan are a little dinged so I guess the previous owner picked up sand or gravel at some point in this boats past which would be normal wear I assume. We'll see tomorrow as I get it back together and in the water to try, try again. But right now, except for a normal amount of corrosion to the aluminum housing it's looking pretty good for getting under way. Thanks again for your helpful advice. Keep posting to let me know your thoughts and any tips or tricks you might have up your sleeves.

Re: OMC Turbojet 115 HP - Please help!

One thing I do know about these turbo jets is that they have to run about 1100 rpm at idle. If you set them slower the gear box will "clunk" all day when there's really nothing wrong with the box. Remember were're dealing with a jet here, not a regular OB.

Re: OMC Turbojet 115 HP - Please help!

I don`t remember the drain screw being under anything. Look at BRP parts, should see the drain on the parts breakdown. I like these things, but the gearcase and pump parts hard to find and pricey.

Re: OMC Turbojet 115 HP - Please help!

Diagram looks like the fill plug might be up under the intake sceen? I'll check it (right now it's raining like heck). I'll get back to that later.

Next question, I got the impellor unit off, worked on the three screws (with heat, a hex key and a Vice Grip and only busted one but there's still a stud so I'll leave that for now) that hold the cone over the impellor fan blade bolt and I want to take off the impellor fan blade. It would be my guess that I have to put the unit back on to the drive shaft to let engine compression allow me to get the 1 1/16" (head size) bolt off with an impact wrench or just muscle. Does that sound like a good plan? It's the best I've got

Okay, so after that's done I can grind the blades to give me clearance from the SS Collar in the housing (it's definatly got a gouge from a pebble or rock and from the inside looking through to the exhast side it looks like that SS housing collar is either definately warped or got corrosion under it to cause a lump that the fan blade hits besides the scratches from rocks and corrosion. I'll sand the surface as smooth as I can and take care of the scratches, then move on.

Is there a torque setting for the fan bolt or is it just two farts and a grunt?

Thanks for any help you might be able to impart.

Re: OMC Turbojet 115 HP - Please help!

Yes, getting the impeller off will require you to reinstall the jet unit. What I have done in the past is remove a spark plug and feed a foot or so of nylon rope into the cylinder. This will prevent the engine from turning and allow you to loosen/torque the bolt. 70-75 ft lbs with blue locktite on the threads upon reinstall.

The drain plug is just in front of the intake screen. I suppose it could have been slightly covered, for some knucklehead reason, when the drivetrain was installed into the hull. Mine is centered and is a flat slotted screw approx 3/8" diameter.

Re: OMC Turbojet 115 HP - Please help!

Okay, so 70-75 lbs torque...no problem. Thanks for that and I'll check for the drain plug and see whats up with that. That oughta' just about do it and then a water test.

Then the hard question....now that OMC (ie: Crowley Marine) says major parts are NLA ie: Impellor, Housing, etc, etc.....who's got parts when I go for a real rebuild this winter? There must be some aftermarket suppliers out there cause used parts wouldn't necessarily be any better than what I already have. '96 isn't really ancient although I understand not too may of these were made during a short two year production. You guys must have some suppliers. Also, is there any real advantage to the "high performance kit" and how much speed (10 knots maybe to top speed?) would it add if I went that route?

Thanks again for all your help.

Re: OMC Turbojet 115 HP - Please help!

The performance kit you mentioned and all unavailable parts can be found at turbojetmarineproducts.com. They will also be your best resource for info as most omc dealers have never seen a turbojet. Like yourself I was dedicated to my boat and have squeezed as much performance out of the setup as I could.

I found the performance kit to be partially usable. The nozzle keeps the boat running relatively straight however agility in turns seems a bit diminished. The extension does seem to assist in preventing cavitation and jump the boat on plane a bit quicker. The main dissapointment with me was the cool intake grate. Custom fit, smooth curves but they spaced the grates apart too far such that debris entering the pump will not pass thru the impeller. This was annoying as hell when fishing lakes where alot of chip is present. It now sits on a shelf in the garage. I did not see a 10 knot increase. Maybe 4ish at sea level.

There was actually a four year production of these jets before they shut down. Mine is a '94. Understand that these were the forerunner of the minijets. Other manufacturers copied improved and modified. All this being said the sooner you realize the limitations of the setup the more you can enjoy the boat for what it is. These jets are not speed demons but relatively dependable shallow running workhorses.

Re: OMC Turbojet 115 HP - Please help!

Hey....wow! This baby is a GO MACHINE!!! I got it out on the lake today and that sucker really hauls. I'm impressed. Since I've never had a boat before (let alone a jet boat I had a real blast with it today.

Wanna' get a real laugh though? When I hooked up the steering after installing the cable I must have reversed the bracket cause turning the wheel left sent me right and vice verse. LOL What a trip. I'll straighten that out tomorrow before I take it out again Great day on the water. Thanks y'all for your help and advice. Without you guys it never would have made it to the water.