problem with 1997 speedster dual rotex engine

[nmharris]

Hello all,

This is my first post dealing with engine trouble.

I have bought a 1997 Speedster Jet Boat about 4 months ago. I have ran it about 7 times, mostly going well. I have had some cavitation problems but I expect that from older impellers and air getting into the jet drive from the hull. It runs about 50 on the water, much faster than I expected of it. The port engine was replaced early on, I spoke to all of the owners on the phone ( 3 of them).

The problem I am dealing with now is that the starboard engine is idling about 1k rpm and will not go any faster. Add some throttle and it dies. It would not even start till I started trouble shooting - I should add that that engine has had little by little increasing problems running out on the water. It would run
with little enthusiasm, till about 20 minutes into the ride - then it seemed to be fine. The time after that it would run poorly, taking longer till it ran stable. The last time out it ran poorly for about an hour - then it just quit working all together.

I have checked all the cylinders from the engines, and they read 120 ( i understand that 150 is ideal, but maybe it is just my compression tool). I swapped carbs from the 2 engines just to check that as a suspect. No difference. I even ran the fuel line from the port side to the starboard, that did nothing either. I should mention that the carb on the troubled engine seemed to spit out large amount of oil, kind of a back fire maybe.

I checked the pressure in the oil system to see if it was losing pressure ( it is using Walmart NMMA tc-w3. It has used that oil from when I picked up the boat.

I checked and swapped spark plugs, checked that they where getting electricity ( I do not know how to check the timing though).

I swapped batteries and looked over all the spark plugs, swapping them too. I don't think that it is the electrical system, but I should rule nothing out.

I do notice that when I removed the large purple muffler (that contains water in it) the rpm's go up. As well, if I put my hand over the rear exhaust the engine starts to die.

So this is where I am at, I do not know what to check next. Both engine start and run, but the starboard engine is still idling from 1k to maybe 2 k, and dies with throttle. I did add some lube to the PTO flywheel, but I didn't expect that to do anything.

If someone can help, much thanks in advance.

Nathan Harris

 

[kcr357]

Can you turn the driveshaft by hand?

 

[nmharris]

Yes, both motors have about the same force to turn the driveshaft by hand.

 

[kustomkarl]

I would start with basics. Start with a compresiion test.
Here is info to doing it properly;

You'll need a compression tester. Go to Auto Zone. I think they sell for like $25.00. The compression gage, will screw in the cylinder head in place of the spark plugs. To test compression, remove both spark plugs. Place spark plug caps on the plug cap studs near the cylinder head to ground the empty caps. This completes the circuit of the ignition electrical system and prevents any electrical problems from the caps being un grounded. Using the correct adapter for the threaded end of the tester,( same length of the spark plug threads length)screw in the tester in one plug hole. Hold the throttle wide open. Push the start button. Watch the compression gauge, when it peaks out at the most compression, let go the start button. Read the psi number. I would do it 3 times to be sure it is accurate. Check both cylinders the same way. The ideal compression is 150 psi per cylinder. If it is less, it's not a problem as long as they are close to being the same. If the psi is less than 90 it might need be time for a tear down and a rebuild. If the psi in 1 cylinder is say 140 psi and the other is 80 psi you need to tear down and repair. This difference is a lot then there is a problem. I hope this helps you.

That's an old machine, it could be the problem.

You said you swapped the carbs and fuel line so it might not be fuel related so it must be electrical if mechanical it is good also. Remove the spark plug caps and cut off 1/4 in. off the wire and re-install the cap. Use fresh gaped plugs. check the spark now. If it seems low it might be in the Magneto. If it has low spark pull the cover to the Mag and look for corrosion, in or around that area. You should also check all your wire connections for corrosion. Be sure all the battery cables are clean and getting a good connection.

Was it by chance back firing at any point?

Let us know how you make out. Were here for you.

Karl

 

[timmyboy76]

make sure the "inline" fuel dilter/seperator is tight and the o-ring is good...can replace it with o-ring from Ace, home-depot..etc

check the pulse line for crack/not securred properly...also the "return" line

 

[nmharris]

I jumped the gun, and tore apart both engines - removing them completely ( I wonder if I should take pictures and document everything?) BTW, it took only 4 hours to do so, if anyone wondered. It turns out that the gear to the side (ROTARY VALVE SHAFT) that should be turning the 2 cycle oil in not moving at all - in the bad engine ( (can you get the ROTARY VALVE SHAFT off with out a special tool?). There is grey liquid ( oil and water all up in the oil pump unit ). There is sand and debri in the colling system ( that is probably not major, but I will clean it out. The gaskets all need to be replaced ( this baffles me, because it had good compression). The exhuast too looks like it has gray gook, and fine sand debri all over the inside.

I will take clean everything up repaint the engines when back together with 500f engine paint.

I was able to get the main large bolt off of the fly wheel holding the magneto, but I dont have the tool to get the flywheel off. Any ideas? from anyone?

As well I dont have the tool to get the rear PTO flywheel, any ideas there?

I am thinking of resealing the hull base, since the engines are removed, to illiminate any air from getting into the jet pump. And, thinking about getting better impellers.

Should I close off the 2 cycle system and just mix the oil with the gas, seems like a good idea to me ( less parts to deal with)?

I should also mention this: please dont laugh. On the good engine: I did not tighten down as much as I should have the 2 bolt that hold the upper carb blk chamber to the carb. So when I did a compresion check and opened up the throttle, on of the bolts went down into the inner carb, making a small hole in the thin metal plate (ROTARY VALVE) that spins for the 2 cycle oil, and seizing the drive shaft, when I get it apart I will see how much damage it did to the threading. - talk about bad luck

Anyone else have any comments about what to look for or what to do before I repackage the engines?

I am going to make my own gaskets from a thick water tight material that i bought from the Auto parts store for that purpose - making a template from the old torn gaskets.

 

[timmyboy76]

harris...use the 3-bolts that hold the exhaust pipe to manifold, and thread those into the flywheel about 1/4in, then use a harmonic balancer (rent one from auto store), to pop the flywheel.

For the RV plate, need to inspect the surface, make sure it aint all gouged up and replace the plate itself, since it has a hole.

Sure you can remove the RV assy, only problem is, you'll need to also, crack the case, to get all the shaving out, then make sure, the assy, isn't bent, then you can replace the "brass' gear only.

You can install a "block-off" kit, where the oil injection system is, but that wasnt the failure, but if you do, then you still need the 2-lines from the tank, that goes to/from the case, since the RV assy, still needs oil

 

[nmharris]

I cannot get the flywheel off using a harmonic balancer puller, I pretty much broke the puller. Is there a secret to getting it off? does it need to turn or does it just pop off?

thanks,
Nathan