1996 S115TXRU rebuild Help

[Kndjen86]

UPDATE-S130TXRU
I purchased a 1998 cobia at auction this year. My first boat. I rebuilt the carbs and got the motor running. It was still bogging down in the water and on my first real day out the motor died on me twice. I took it to our local mechanic. Piston rod broke at crank. 3 grand to do a full rebuild. uGh! So I figure I’ll do it myself. I currently have it broke down. Tomorrow I start into the power unit. I have to determine if the crankshaft or internals have any damage. I have a couple questions. One is does this motor have sleeves? I cannot find a part for the sleeves. If it does not have sleeves and I have to get the cylinders bored then do I bore all cylinders or just the damaged cylinder? Also the prop shaft is bent. I’ll be replacing that. What tools do I need to pull the shaft? Also is there a walk thru or step by step for pulling this shaft from this motor? Thanks everyone!

[boscoe99]

No sleeves.

You do not have to bore all cylinders if just one or several need to be bored.

Service manual will be highly desirable. No specific videos that I know of. Maybe look at dangar marine videos on youtube.

[TownsendsFJR1300]

And being a rod broke, I'd suspect some damage to the crankshaft..

I'd pull that powerhead apart before buying any parts.

Open up this https://www.boats.net/catalog/yamaha.../1996/s115txru to bring up all your parts.

It'll also say if their available or not(especially with the age of the engine)

If used in sale water previously, may want to inspect closely for serious corrosion...

And plus one on the shop manual...


Good luck and post back what you find..

.

[Kndjen86]

Ok I need to update this as well! I made a typo. It’s a S130TXRU.

[Kndjen86]

I have purchased a shop manual. Have not read to far into just yet. Going to really break into it tomorrow when I get into the crankcase.

what’s the best option to clean the corrosion? Honestly the head and covers are not overly expensive. I have had the motor running and it has good water flow. While I have it tore down though I’m going to clean all the water passages as best as I can.

[boscoe99]

It is no wonder the rod broke with the damage to the top of the piston.

[Keithbaja]

I can't really tell on my cell phone, but that piston is hammered. Thinking pre-ignition. Piston rod pic would be nice. They don't break easily. Most times a rod breaks from water intrusion.. think hydraulic a rod.. I would be looking at the crank journey with a trained eye. Like someone who has been doing this a while. Aka machinest. Inspect,, inspect,,inspect before buying any parts. I don't understand,, why you are thinking about boring cly. Maybe dressing with a hone...

[TownsendsFJR1300]

Re corrosion, for the block/head, covers, pretty much manually. Thin screw driver, small toothbrush style SS/brass brush (where it'll fit).
(The corrosion, for that old an engine doesn't look terrible, likely a fresh water run engine).
For removeable parts(again head, etc), you can use a "Mix" and let it soak-I forgot what folks have used previously.

You can clean the top of the piston with a wire brush, brake/carb cleaner will speed up the process. I'd inspect very closely the top piston ring groove (pistons out)
that the crown of the piston isn't damaged (crushed down / pinching the top ring.

As noted, I'd dig into what is actually damaged/needs replacement (if available/ worthwhile) before spending time cleaning the block , etc.


.

[Kndjen86]

Thanks for all the info y’all! Much appreciated. Used motors in the 100+ HP range cost between 3-5k around here. I have had to redo this whole boat this summer from fiberglass work to redoing the seats to rewiring. So I figured I might as well rebuild the motor myself. I’ve learned a lot about boats. Made a lot of mistakes and have better knowledge when I actually get a newer boat. I should have checked the compression before I started. Learned that one the hard way. So far costs I have figured up.
gasket rebuild kit $309
piston rod assembly $220 per rod
prop shaft $75 already purchased
i figure I could rebuild the whole engine for around $1500.
probably going to have to replace the control rod as well. Pretty sure I broke it when pulling the engine. Plus side only thing that broke besides a small oil line.

1. For the crankshaft. I will post more pictures as I get further into the block. I have a mechanic that is going to mic the crank. Also I have a machinist neighbor going to have him double check my mechanic.

2. For the block. I will post more pictures as I get into the block. I have a couple options near here. Going to start with my machinist. I’ll have him check the cylinders. I also have a couple custom diesel shops I’ll take the remaining rods and pistons to.

[Keithbaja]

No sense putting a mic. On the crank !! It's nicked, scratched, damaged or not. Really simple. If a light scratch try croucus cloth to polish. no way in hell will a mic do any good except checking for out of round.. you are way in over your head. Stop and save yourself time,, money,, headache

[99yam40]

where did the rod come apart at?
you said at the crank, but does that mean the cap came off?
did it hit anything in there?
a rod or even a piece of a rod flying around inside the crankcase can do a lot of damage

[Kndjen86]

So updates for everyone. Thank you for all the information. The wrist pin broke and the connecting rod was bent. The motor was still running with the rod running into the exhaust port. The cylinder wall was cracked as well. So I have now pulled the whole motor off the boat. If anyone needs parts let me know! Trim tilt and all other parts worked great! I am planning on repowering. I am going to look at a 90HP Mercury tomorrow. Any advice on hooking everything up would be great. Thanks again everyone.