Lost # 6 cylinder today

[RidgeRunner]

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???

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.

[turbinedoctor]

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

[turbinedoctor]

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

[turbinedoctor]

I dont know if I put it into words as well as it could be, so here are some pictures of the pistions.

[turbinedoctor]

My other thought is instead of buying a piston at $100.00 is to take the non beveled piston to a machine shop and have it beveled.

Any thought either way?

[RidgeRunner]

Cut it. I don't know the reason for the bevel unless there is a clearance issue in the block at the combustion chamber or different porting from one block to another. If you don't cut it you would have more compression on that hole or worse, interference. You can take it to a machine shop or you can take out the file and do it yourself. You will get it plenty close enough just don't use anything that will cause a build up of heat and make sure it is nice and smooth like the rest of the piston.
I responded to this thread earlier that the tower of power likes to spin free but was wrong on the rpm. Some of the 150 hp inlines like to spin up to 6800 to 7000 but I read somewhere that the 90 and 115 like fewer like 5800 to 6200 max. The fact that it lived as long as it did is proof that you must have been doing it right all along.
How about the tools, were you successful in locating the tools you needed?

[turbinedoctor]

Originally Posted by RidgeRunner

Cut it. I don't know the reason for the bevel unless there is a clearance issue in the block at the combustion chamber or different porting from one block to another. If you don't cut it you would have more compression on that hole or worse, interference. You can take it to a machine shop or you can take out the file and do it yourself. You will get it plenty close enough just don't use anything that will cause a build up of heat and make sure it is nice and smooth like the rest of the piston.
I responded to this thread earlier that the tower of power likes to spin free but was wrong on the rpm. Some of the 150 hp inlines like to spin up to 6800 to 7000 but I read somewhere that the 90 and 115 like fewer like 5800 to 6200 max. The fact that it lived as long as it did is proof that you must have been doing it right all along.
How about the tools, were you successful in locating the tools you needed?

Since I have 5 non beveled pistons I will probably play with one to do it myself. As to the rpm's the manual calls for 5000 to 5200. I have the largest jets in the carbs to make sure it is rich, use only Quick silver oil and as per two different mechanics which dont know each other, I run premium gas for the octane, helps prevent knock. I have most of the tools coming with the order of parts and found the two tools that are NLA at Powerhouse marine, these two are in my pocession now. If you need to do a rebuild on one of these let me know and I can sent up a rental plan for the tools. LOL