Lost # 6 cylinder today
 

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.

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