Mechanical FLIPFLOP..

[jeffywestcoast]

AARGH..mechanical nightmare , looking for opinions here folks, found another complete engine 70 horse for 150 bucks needs rebuilding, but a friend of mine seems to think i might be able to get away with just honing out the cylinder that is bad on mine and putting a new piston in it and carry on for the rest of the season or at least until i can get the 70 rebuilt...Not sure what is the best bet..|I just want to be back fishing..been too long already without a boat in the water ...guess for a couple hundred bucks it is worth giving the 75 another chance. cylinder has a pretty good gouge in it, will a new piston be able to maintain some compression or am i wasting time and money trying to limp it thru the season?

 

[jeffywestcoast]

the bad gouge is at about 11 oclock in the picture Any thought would be appreciated..Thanks..

 

[jeffywestcoast]

sorry my bad guess this should be in the boat motor trailer section..

 

[trendsetter]

Nope, you can't hone that out. It needs to be rebored but since you're getting a new piston anyways the cost isn't much more.

Not sure what your mechanic is telling you but you can't replace a piston on one of these motors without completely disassembling the powerhead. So essentially it will be a rebuild. You will need to replace the wrist pin bearings on all three pistons and the connecting rod bolts. Also a powerhead gasket set is needed.

Going to the trouble of replacing one piston and trying to get by with one hone job is not worth it when for a couple hundred more the job can be done right and you will have essentially a new motor.

Clearly a ring let go and pieces of it were pounded in between the piston and cylinder head. What does the cylinder head look like? I'm better it looks similar to that piston and will need to be resurfaced also.

 

[jeffywestcoast]

was also told from another guy that races these engines that he has many times replaced a piston and rings and left the other two alone, i just purchased a complete 70 for rebuilt for 120 bucks, we were going to take a piston from the 70 new rings 100 bucks and for 60 bucks for a gasket set and a little resurfacing of the cylinder and cylinder head, and yes it looks just like the piston, the guy i am buying the 70 from is a marine mechanic in nanaimo for years.but a good friend is helping put it back together for beer n pizza, had i been paying mechanic wages to do it i wouldn't even think of it. but to get me back out fishing well the 70 will be getting a complete rebuild bored ,new pistons kits for each cylinder and anything else it might need, i realize it isn't the proper way to do it by scabing it back together but let face it this thing ain't a gem and i only have a month left before returning to work in the oilfield, if i can get it back together and limp it along for a month i would be happy to do so. As i am missing alot of fishing right now.

 

[jeffywestcoast]

Also trendsetter i value your opinion as you have stated you have rebuilt many of two-stroke engines and if i am just opening a can of worms by doing it this way i will put a stop work order on the project until it can be done properly, i have 1000 bucks set aside to rebuild it so maybe just going with the full/full is the better way to go. probably shouldn't take much longer anyways with them both apart like said, just an afternoon in the machineshop.

 

[trendsetter]

Yep, your friend is totally right, you don't need to replace all the pistons or rings at once. You can certainly replace a single piston and leave the other two if they are in good shape and still have decent compression. Did you do a compression test on the top and bottom cylinders before taking it apart? If they were both over 100 PSI then you don't need to replace them at the same time if you just want to get it running.

The problem you have is that cylinder needs to be rebored. Even with a new piston and rings it will have low compression if the cylinder is gouged. The engine will run like crap and you will be out a few hundred bucks!

Also you have to be certain the donor piston is the same size as the one it's replacing. It could be standard size, .20 over, .30 over or even .40 over. The number should be stamped on the head of the piston. So you'll need to pull apart the donor motor first to see what's in there.

 

[jeffywestcoast]

yup roger that , the reason my friend said for not going into the machining is that the bolts holding the water and exahaust portion of it are 30 years old and most likely are going to break off, and cause a much greater headache and cost factor, there has to be a point at witch it is not worth putting any more money into the 30 year old outboard, after returning to work fulltime in the patch im sure it will be not long before i find a completely newer and better fishing set-up, i was at my buddies looking at motor again, my buddy thinks he can get most of the ridge out and that the gouge is really not that bad. he had a similar gouge in his 90 evinrude that he took down the ridge and ball honed it and scabbed it back together we will have to see, here is the picture of the gouge in question and yes the two other cylinders still have very close to stock compression

 

[trendsetter]

If the engine is in poor overall condition with rusted bolts etc then it's not worth putting any money into it in my opinion. There are a lot of clean outboards out there that need rebuilding that are much better value. It costs about the same to rebuild a 1998 outboard as it does a 1980 outboard.

I've got one sitting on an engine stand in my garage that needs to be rebuilt. I'd keep an eye out for a replacement motor and sell that one and the donor to recoup some cash.

 

[jeffywestcoast]

the bolts are not rusted they are just coroded , outboard was in good working condition 2 weeks ago when it started makin a funny noise n right away i shut it off and ran in on the kicker, will have to see i guess will let my buddy see if he can make it work, just need it to run to charge the battery so i can bring my downriger up n down

 

[jeffywestcoast]

what would your rebuild total cost be ? keep me posted maybe you can rebuild one for me or help me find a suitable replacement.i am assuming the donor motor is not total junk apparently it is complete and electrical components are interchangeable i am just across the pond in nanaimo and would consider coming over there with my truck if i can find affordable replacement, 50 -70horse tops... probably in a month or two. there is a 90 evinrude in victoria running for 500 but i know it is probably to heavy for my 16' shallow v knc.

 

[trendsetter]

A rebuilt mid 90's 70hp with power trim / tilt and in good overall condition usually goes from 1500-1800 on the used market. A dealer would probably charge around 3k.

I could probably find one or rebuild one for you if you wanted. I rebuild these things more as a hobby then as a job but I'm sure we could work something out.

 

[jeffywestcoast]

Good to know trendsetter i have you on my radar now, could be a possible motor in my future but like i said before in the forum , i can only put so much lipstick on a pig and will seriously need to be looking into a completely upgraded hull and motor as Sportfishing is something that will always be on the front burner for me .

 

[jeffywestcoast]

i found the model number #j75trlcnd
and serial number #c8148694
if i am correct it tells me it is a 1982 i am asuming that it has never been rebuilt but untill we split the powerhead i wont know, if they are stock .20 or .30 over..still waiting for the donor motor to be dropped off, it's on its way i have gaskets and piston and rings able to be shipped next day once we know the size. parts are pretty cheap if you get a marine mech discount i found the gaskets for 60 and piston kits from sierra for only about 60 aswell, on new piston and three sets of rings and a gasket set is all it is going to cost me to putter back together.

 

[jeffywestcoast]

going to see what can be made of the two this morning, donor motor is complete and will require a going over to see what if any parts can be re-used..

 

[jeffywestcoast]

found a mint block and stock pistons ,just waiting on gaskets seals and rings ,it is all going back together within a few days, for around 300 bucks a some beer n pizza..

 

[jeffywestcoast]

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