Rebuilding Power Head

[KYHunter2]

Re: Rebuilding Power Head

Theres alot of different recommended break in procedures.

I followed the 10 hour breakin , as far as one speed / rpm's , not minutes but just keep changing rpm's.

I keep my hand on throttle and never leave it at any certain speed for more then 15-30 seconds.

Right or wrong its worked very well.

I retorque the heads after first couple hours then after the 10 hours.

KYHunter

 

[Indymike]

Re: Rebuilding Power Head

What pistons are you using? What is the finished bore size?

 

[Mark42]

Re: Rebuilding Power Head

KYHunter2 has the right idea. You want to vary RPM's during breakin. Don't just leave it at 2500 for the first two hours. Keep moving the throttle.

Unless something was assembled wrong, chances are it will pass break in with no problems.

 

[funpilot]

Re: Rebuilding Power Head

If I remember correctly, the loctite primer allows you to start the engine before 12 hours of cure, something that might be important in a service shop, but not at home.

I used a 13mm socket to hold the needles in the small end of the rod. It allowed me to slip in the wristpin, by pushing the socket out.

The end caps install a lot easier than the book says. They are in halves with irregular cuts, it is almost imposible not to find the mating halves and then install carefully. If they don't pass the fingernail test, just loosen, align, and retighten. If you oil the cap bolts, you will get about 20% higher torque then dry. I didn't oil on the 90 hp.

50:1 in the tank. It also verifies that your VRO is working as you use about a pint to a quart from your VRO in 12 gals. Don't forget to pump up the VRO in-line bulb, or you will get a warning horn on start up.

fp

(note edited to remove picture of rod. it was too big)

 

[KYHunter2]

Re: Rebuilding Power Head

I've had good luck using the end of a piston pin, to install needles.

Stick it through the con-rod, as it will go .

Using vaseline to hold needles , as I install them around pin.

Slide out pin carefully and install in piston.

The vaseline holds them very well.

I DEFINATELY WOULDN"T , oil , or anything else on the con-rod / stretch bolts.

And avoid re-torqueing, too many times.



KYHunter

 

[MASTER Brian]

Re: Rebuilding Power Head

Mark, I am building this powerhead myself. I bought a rebuild kit and had the engine machined.
When you say, "first 10 minutes are high idle (about 1200 - 1500 rpm) running only do not idle". Do you mean the boat shouldn't be moving? Or should it be moving at just above a normal idle speed?

KYHunter2, I'll just use 2-stroke oil then and lube it up really, really good. I just figured an engine pre-lube would stick better. Also, I will keep the throttle moving.

Mike, I'm running Wiesco piston's 30 over. Why do you ask?

I also guess I won't oil the rod bolts and just torque them to spec. Like I think I mentioned I didn't see the oil technique mentioned on the 150 rebuild, but it was in the 200 rebuild. Interesting... I'm also hoping I am correct in the torque procedure, because that wasn't real clear. I'm assuming I tighten one bolt to say 10lbs, then the other to 10lbs, then go up a few lbs to say 15, then 20, then 25, then 30lbs. Am I correct??

I have kept the rods together with their end caps in the right order and will pay very, very close attention to that.

So, 50:1 in the tank, prime the VRO and I should be good. I wonder why the book says 100:1, because that would seem to be very little oil. I don't forsee a problem with the VRO, as I got a new one, but things happen, which makes me concerned that if it doesn't work, is 50:1 enough oil to save the engine during a breakin??

Sorry for all the question, but with this being my 1st PH rebuild, I want to ensure I am doing what needs to be done. Thanks for all the help!!

 

[MASTER Brian]

Re: Rebuilding Power Head

While I am at it, I have a question about chamfering the ports. I was told by the machinist to take some emery cloth and go around each opening about 4-5 times to take the sharp edges off. Is this sufficient, or do I need to do more?

I have some grinding tools for a dremel and for an air grinder, would it be better to take those to it very carefully and put a bit more of an edge on them? I was told by someone that the factory didn't use to chamfer the edges at all back when this motor was made, which is why ring failures are common. Also, from what I read, it's really most important with larger ports, which this motor doesn't seem to have.

I spent about 1-2 hours last night going over all the ports and there aren't any sharp edges and they are visibly more rounded. Just to check myself, I had my wife feel them and without telling her which ones, I had and hadn't done, she could tell a definate difference.

 

[KYHunter2]

Re: Rebuilding Power Head

Im surprised that your machineist , told you to chamfer the ports.

IMO, thats part of his job.

As long as you break the sharp edges , you'll be fine.

Mark, explained to you , that if the VRO is working, and yo add 50:1 to tank you'll have 25:1.

Which is double oil, 100:1, is half the recommended oil. ( gas : oil) 100 parts gas , 1 part oil.

I do at least 3 steps when torqueing, probably more.

As long as you don't just crank them down , you've got the idea.


On head bolts be sure to follow the torque sequence, and 3or 4 steps is good.

Just curious , what manual do you have ?


KYHunter

 

[MASTER Brian]

Re: Rebuilding Power Head

I'm a bit suprised he didn't do it either, but he told me up front, he wasn't planning on doing it. It isn't/wasn't figured into his pricing. He told me I might as well do it and just save the money, because it wasn't that hard to do, just time consuming. Same thing with the high spots in the head from the pitting of the ring.

The sharp edges are broke, I'll look them over once more before washing the block and call it good.

I realize that if the VRO is working, I'll be double oil, but what if it isn't for some reason? Is 50:1 going to tear anything up, if the VRO isn't working? I would think I would be able to tell if it is or isn't because I would think it would smoke a lot more than normal. I just have a doubt, because it's a new unit and strange stuff tends to happen to me.

Sounds like I'm good on the torque thing then and 3-4 steps is what I normally use as well. The manual just made it sound like a special tool was needed for the rod caps, and didn't cover much other than saying that.

I have both a clymers and an OEM Service Manual from OMC. I've been using the OEM manual for this.

 

[KYHunter2]

Re: Rebuilding Power Head

Your motor has the precision ground rod caps.

And yes theres a alignment tool designed for this purpose.

The ones I've rebuilt were the older style, sanded con-rods no tool needed.

I can't say if you can do yours without the tool or not. I do know its critical that they are correct.

As far as your oil questions.

You need to either verify that the VRO is working .

Or disconnect it , and add 25:1 oil in gas.

It needs to be double oil during break in .

I wouldn't rely on extra smoke to verify VRO is working.

KYHunter

 

[Mark42]

Re: Rebuilding Power Head

"So, 50:1 in the tank, prime the VRO and I should be good. I wonder why the book says 100:1, because that would seem to be very little oil. I don't forsee a problem with the VRO, as I got a new one, but things happen, which makes me concerned that if it doesn't work, is 50:1 enough oil to save the engine during a breakin??
"

Regarding the reference to 100:1 in your manual, some of the motors from the 80's were supposed to run on 100:1 mix, but time showed that was too little oil and there were engine failures.

If you do some searches on 100:1 you will find this topic comes up periodically. From what I have read, practically no one does a pre-mix at 100:1. And those that do, only use synthetic oil. And do so at their own risk. :^

Good luck with the rebuild.

And remember to keep lube on the cylinder walls and test turn the basic crank/rod/piston assembly to ensure nothing is binding before finishing assembly of the power head.

 

[MASTER Brian]

Re: Rebuilding Power Head

KYHunter, can you tell me what the alignment tool does?

I'll call the company I bought the rebuild kit from and ask them. I don't recall being told I needed anything special for this motor. I think the biggest concern was the installation of the needle bearings.

I guess, I don't see what the tool would do. Like I mentioned I know the caps are a "controlled break" and have jagged edges that need to be installed correctly, the manual also points out making sure the dots on the caps/rod face the flywheel.

As for the oil, I'll just keep a very, very close eye on the VRO/tank/bulb and hope it works.

 

[KYHunter2]

Re: Rebuilding Power Head

On the hand sanded , con-rods.

The direction , they are sanded allows , the use of a scribe, sharp pencil to verify , the caps are aligned perfectly.

The ground rods, have the grind marks horizontal , where you can't use , the pencil, scribe.

The tool , clamps them in alignment for you and you just torque.

At least thats my understanding.

As I said I work on older motors , for the most part.

And haven't had the chance to use the tool.

The dots are just to get them connected properly, but not adequate for the true alignment.

As well as assuring the oil holes face the right direction.

This is a critcal step, need to be as close to perfect as possible.

Not alot of margin for error.

If your used to using the VRO, you should be able to guage the oil use ,from past experience.

To know its operating correctly


KYHunter

 

[KYHunter2]

Re: Rebuilding Power Head

Heres the best tip , I can give.

Its obvious, you want this to be right.

Keep everything EXTRA clean.

Take your time , and be sure everything is done, per the manual.

No, its good enough , not on these motors.

As long as you verify , the motor will turn , freely, smoothly .

With no hint of binding , wobble, etc. etc. etc.

You'll be fine.

KYHunter 8)

 

[MASTER Brian]

Re: Rebuilding Power Head

Well, I called the place I bought the rebuild kit from and they said to use 2 stroke oil on the rod cap bolts, not to use the alignment tool, just make sure they are perfectly aligned after finger tighten, then torque to 10lbs, 20lbs and then 30 lbs. He said they don't use the tool anymore and it is about $400!

Got some other good pointers I hope. They also told me to tighten the crankcase flange bolts to 95 in. lbs. vs. the 84 in. lbs. the book calls for, because 84 isn't enough. Then they said not to use the washers when installing part of the carb cover, because if the bolts come loose, they'll get sucked into engine. Good point! They said only to loctite the 4 bolts that hold the bottom cap into the ring...(I believe he was talking about the ring cap on the bottom of the motor). The other thing was to use gasket sealing compound on all threads to act as a loctite and a sealer.

Does all of that sound good? ....or would anyone else do some of that differently??

Hopefully, I'll get the pistons in tonight and be able to move past that step.

 

[MASTER Brian]

Re: Rebuilding Power Head

One more thing, while I'm thinking of it...I believe I need to re-attach/move some of the flywheel magnets. One or two seemed to be a bit loose, when I pulled it apart.

Seems like someone said, space them evenly apart then glue them back in with JB Weld. Does that sound right??

 

[funpilot]

Re: Rebuilding Power Head

The VRO delivers oil depending on the load on the engine. The oil delivered varies somewhere between about 100:1 and 50:1, depending on the installation and load. The 50:1 as premix is to assure that the VRO is functioning, and that the engine is broken in with some extra lubrication. The OMC people spent a lot of money and time tweaking the system until the had it right, so VRO varies from year to year, especially early on.

25:1 is the result of using 50:1 premix and 50:1 VRO (approx.) at the same time. 50:1 is half as much oil as 25:1, and 50:1 is twice as much oil as 100:1. Your engine will still break in fine at 50:1 on the chance that the VRO doesn't work. Please limit your WOT after the first hour, and until the second hour is complete. Give the engine plenty of time to stabilze at a lower RPM (two or three minutes) after the application of brief periods of WOT.

As I said before the rod caps (even the precision ground ones) are easy to install without the special tool, if you are very careful and check them for perfect alignment as you go. If not perfect, just loosen and retighten until they are right. Your fingernail will tell you much.

I doubt ring failures are caused by a lack of chamfering, although it is possible in theory. Some use of the engine should mitigate the sharpness of the edge of the port. My money is on carbon build up as a failure mode.

fp

 

[MASTER Brian]

Re: Rebuilding Power Head

FP,

Thanks, I couldn't believe that the fingernail test you mentioned earlier woulnd't suffice, but never having rebuilt a PH, I want to be certain.

I too believe my issue was caused by carbon as well, just from the looks of things.

I'm still not clear on the 1st 10 minutes. Is that 10-15 minutes fast idle on trailer sitting in water or 10-15 minutes fast idle with boat floating in water underway? Can I do this at home with the motor in a tank of water...or would that require a test prop?

 

[red boat]

Re: Rebuilding Power Head

Masterbrian and all, Wiseco pistons used to have a special break in procedure because they were forged not cast pistons. You might want to call Wiseco tech support and talk to them to verify before breakin because when I put the wiseco pistons in my 1990 XP-200 there was a 2 hour idle period before any throttle was to be applied!! That is a completely diffrent breakin than the OMC manual recommended (again due to factory pistons being cast and Wiseco's being forged).
Do not do breakin at home with a hose! Breakin with the motor fully in the water boat off the trailer and NOT in gear. Please post back with breakin procedure recommended by wiseco tech support.
I took my block to a local johnny/rude dealer and he used the fixture alignment tool to put the rod caps on and he only charged me $25.00. I chose to do that just for "peace of mind" knowing they had been installed correctly.

 

[MASTER Brian]

Re: Rebuilding Power Head

I called wiseco and the guy told me they recommend doing a heat cycle of the engine to get the pistons to conform to the cylinder walls.

Basically, they say start the engine with water and let it get to operating temp, then shut down until room temp, and repeating 2-3 times. After that he said follow the manual, but said it wasn't real crucial after that, just use common sense. Basically, start slow and build up, varrying the RPM's.

I don't plan on breaking the motor in on a hose, but I have a horse tank I can submerge the motor in for the heat cycle. I don't see much problem with that, since the prop won't be spinning and it'll get plenty of water. Most likely, I'll just hull it to a buddies house and put it in his pond or take it to the lake on a weekday afternoon.

Thanks for the heads up.