Lost # 6 cylinder today

turbinedoctor

turbinedoctor

God
Well my old faithful finaly let me down today. The family and I put out of Kiptopeake and started heading for the fouth island to do a little fishing, but just as we got to within about a half mile, it started with a slapping sound. I quickly shut it down and checked under the hood but every thing looked good. When started again it did not want to idle and ran rough. Not knowing exactly what was wrong I shut it down and started trying to figure out how to get back to the landing.

Remembering I am a Boat US member I decided to give them a call. They were there with in 45 minutes and started the tow of shame. I just came in from looking into the problem and found that the #6 spark plug had been flattened and the piston is pitted and abused. Looks like a rebuild, used motor or new motor.

Does anyone have experience rebuilding inline 6 cylinders?

:sad:
 
i have a freind of mine in Youngsville NC that was one of the best rebuilding those things, I don't know if he would mess with one now. It does take a special set of ring compresors. BTW, if it was running rough, odds are you have more than one cylinder down, I've seen those things with 2 dead holes and two barely above 75 psi idle all day long. You might want to think about repower, they are geiting a bit old.
 
sorry to hear about the misfortune, but this would be a great time to re power and welcome your self to the world of loop charging.
 
I wouldn't both with a rebuild way to expensive for that engine. BUT i suspect you can find a good powerhead for next to nothing if you keep your eye open. Lots of Merc inline six still available - most have rotten electrical harnesses that do them in. You should look into how far back a powerhead swap is possible with your mid before throwing in the towel.

Kamikaze
 
I replaced my 165 inline 6 I/O mototr only with a crate motor I paid 2K for a few summers ago. Labor was another 1K,...and overall I'm very happy with the results.
 
Yeah I think a rebuild is out of the question but I have a spare parts motor almost identical to this one. I will look into swapping powerheads and going the cheap route for now, but first I want to take this one apart to see what happened inside. If it's something like a weak link that got loose and into the cylinder I may consider buying a used motor and stepping up the HP to around 115 or 150.
 
Has anyone had sucess with running 115 hp carbs on a 90 hp inline 6? They are so close to the same engine the only difference I can find is the carbs.
 
Sorry to hear obout the tower of power motor. #6 was the one that always went out. I know they don't like running lean. Not positive about the difference in the back drag carbs. Looking it up in my shop manual but it doesn't cover them very well. The main/idle tube jets are different.

Book says 90hp .070main/.092 vent tube
115hp .072 or .074 main/ .092 or .096 vent tube
Depends on serial number.

I rebuilt a 90 inline 6 for a friend back in 1995. The way the pistons go in from the front, all at once, all on the crank as an assembly with very little clearance it really requires the special ring compressing tools and patience. To replace a piston or two is a lot of work because you must remove the crank to take a piston out (no removable cylinder heads)

Whatever you do, do it fast summer is about over. Hope this helps.
 
Last edited:
RidgeRunner said:
Sorry to hear obout the tower of power motor. #6 was the one that always went out. I know they don't like running lean. Not positive about the difference in the back drag carbs. Looking it up in my shop manual but it doesn't cover them very well. The main/idle tube jets are different.

Book says 90hp .070main/.092 vent tube
115hp .072 or .074 main/ .092 or .096 vent tube
Depends on serial number.

I rebuilt a 90 inline 6 for a friend back in 1995. The way the pistons go in from the front, all at once, all on the crank as an assembly with very little clearance it really requires the special ring compressing tools and patience. To replace a piston or two is a lot of work because you must remove the crank to take a piston out (no removable cylinder heads)

Whatever you do, do it fast summer is about over. Hope this helps.
Click to expand...

sounds like you need a 4 bolt rebuild.
 
What year is the 115 and what year is the 90. May just be the same motor but from different years for how horsepower was rated (powerhead / propshaft) Believe the older (mid 70's) 90/115 in-line six were the same block/porting and carbs where the only difference. I'd go for it, just make sure you can use/mount your 90 electeonic's ( if newer) on the 115 block if it's older. Your not trying to convert a distributor based ignition system to a CDI switch box are you? Maybe more issues with that than mechnicals associated with swapping the powerheads

Kamikaze
 
If you want to stick w/ a tower of power, just look for a mid 80's 115 and slap it on there.....they are the earlier 150 with 115 stickers, and can be had for 5 or 6 hundred bucks these days.
 
Thanks for all the input guys, I haven't decided what to do yet but one thing for sure, it looks like my summer on the water is over.

The carb swap I was thinking about was to put 115 carbs on my 90 if I get it running again. The block seem to be the same just smaller carbs on the 90.

I finaly got the power head off last night but ran out of time. Will start the tear down soon.

The spare motor I have does the same as mine. on mine it wont go past top dead center on # 6 cylinder and my spare wont go past top dead center on # 3 cylinder. What a kick in the NORTONS.

Am searching ebay for used motors but get scared with no warranty, they all say it runs good, well if I listed mine the day before if crapped out, I could have said it ran good also. Who knows when one will die.

Anybody got an extra 10 grand laying around they dont need, send it my way, daddy needs a new motor.

Turbo
 
Well I must say I am disappointed, all this way and nobody asked for pictures yet, whats going on with you guys, getting slack in your old age?

Well I finaly got it torn down and found whats making all that racket, and I got pictures to boot. It appears that my lower bearing failed, came apart and some of the balls
from the bearing got into the # 6 cylinder.

Pictures are following but I must warn, these pictures are graphic and those with weak stomachs and little children should leave the room.

































This is what a good piston should look like.

100_4634.sized.jpg


This is what a good piston should NOT look like.

100_4626.jpg


That shiny piece in the middle lower half is a piece of the ball from the bearing.

Here is a shot of the cylinder head, not the best picture quality but none the less.

100_4630.sized.jpg


The dark stuff in the spark plug hole is more ball pieces.

And this is what a good cylinder looks like.

100_4631.sized.jpg



Other then a few light scratches on # 6 cylinders wall, which dont show in the pictures, I think it can be honed and reused.
 
Well I think I have talked myself into rebuilding the ol' gal myself. I priced all the parts I want to replace while I have it apart and for just under $2000 I can put it back together almost like new. Parts include crank bearings, rod bearings, wrist pin bearings, all new rings, complete set of gaskets and seals, new bolts to replace the old ones and the speciality tools to do the wrist pins and bearings.




Am I doing right or has insanity set in?

Have some pics of the tear down to post later. So far everything looks good.

Turbo
 
Doc, Insanity is a condition of boat ownership. The fact that you can ask yourself "Am I Insane?" leads me to believe that your mind may still be sound.
Your ability to make a rational decision???:hide:

Break-in oil ratio -- Old School 25:1 (double oil)
I have heard of some going 30:1 on another thread. 25:1 was good enough for all major outboard manufacturers so 25:1 works for me.
No wide open romps for at least 10 hours and then only for a short time say 20 seconds. Do not let it stay at one RPM for long periods of time. The idea is to let the friction surfaces get accoustomed to one another without creating any super hot spots and possible sticking a piston. When you do get some hours on it that motor needs to spin free. Make sure your not lugging the inline 6 they like lots of RPM on the big end. Not positive but 6600 to 7000 is what I remember.

You must love that motor. How do you propose to clean up the damage to the block in the head area and around the spark plug? It would need to be smooth to prevent predetonation. Looks like some irregularities to the counterweights on the crank. Probably where the rod was shearing the bearing. If it were my money I would take the block and rotating assembly to a good machine shop. They can check the bore for roundness, magnaflux the rods and give suggestions on which way to proceed. They would be my "second opinion" and they typically do it for cheap $$$. I would consider it insurance for $2K you will spend on the rebuild kit. When my 90 Jrude broke a ring the damage was similar to yours but I replaced the head, you don't have that option. How do the reeds look? They get pricey for that motor. Pistons are not cheap.

If I ain't mistaken where the motor bolts to the boat is BIA standard, you may want to take a breather and spend some time looking for a newer powerplant. Or maybe a inline 6 for a powerhead swap as someone suggested earlier.
Been there with a 84 inline 90. That motor really screamed. Good or Bad depending on your perspective. My .02
Best of luck whatever you decide.
 
Thanks for the input Ridge, I was thinking along those same lines for break in. I did not how ever consider the roughness in the head as a starting point for predetonation. I was going to wire brush it clean and a little smoother, I may have to work a little harder in there now.

To late to consider a rebuilt power head since I just ordered $2122.00 worth of parts and tools. I do have a parts 90 inline I am going to get the replacement piston out of, I'll check the head on that one. It should be in better shape, if so I'll use that block.

Thanks, Turbo
 
Well I tore down the spare motor and the heads look much better then mine, so I will be using that block, crank and pistons. I am still waiting for the parts to arrive, checked with the supplier and they are waiting for the new wrist pin washers before they ship my order. I am still cleaning parts, so it's no big deal yet. I have to take one piston from my old motor and use with my spare due to damage on # 3 piston. While cleaning the one from my old motor I noticed that the pistons in the spare have a bevel on the intake side, where as my old one does not.

Question: will it hurt to use the piston that does not have the bevel along with the 5 that do?

Turbo
 
You must log in or register to reply here.
Back
Top