Engine rebuild questions, 1980 E25

[BugEyes]

Hi Guys,<br /><br />Started tearing the engine down last night. One thing lead to another and now I have the powerhead on the workbench with the cylinder head off.<br />Main bearings seem good and cylinder walls is unscratched. However there is some play between the pistons and cylinder walls. With the piston in the top position there is no play but halfway down just around the channels it can be moved sideways a bit. Couple of questions thus.<br /><br />1. How much play is too much play and how do I measure?<br /><br />2. Are these cylinders reborable?<br /><br />3. Is it worth it? That question I have to ask myself of cause. There does not seem to be corrosion in the cooling channels but I suspect that the lower unit needs an overhaul as well.<br /><br />Thank's

 

[dolluper]

Re: Engine rebuild questions, 1980 E25

You should have some play for expansion sounds normal smooth wall must be honned before reassembly and lubed [pre-assembly grease]or on the cheap [lubraplate]new rings with openings staggered add it up make your diss

 

[G DANE]

Re: Engine rebuild questions, 1980 E25

An automobile mechanic will jump back with a scared look in his face when he feels the piston slop. They expand a lot when they heat up. If your pistons still has the turn pattern all over sides, without blank spots or areal, they are fine. Was this the rattling one ??

 

[G DANE]

Re: Engine rebuild questions, 1980 E25

Forgot to add: If the crosspattern is still visible in bores, chances are you didnt have to disassemble it at all. I guess your rattle comes from the lower main bearing, If you replace it, look in your manual to avoid ruining the new on, by beating it on the cranckshaft. If pistone and bores look fine, hone and rering.

 

[BugEyes]

Re: Engine rebuild questions, 1980 E25

Thank's for the input,<br />I havn't split the crankcase yet, need to get the correct tool for the bolts as some of them is not metric. Checked again and the play looks big to me but I havn't been inside these engines before so relate it to what I have seen in other types of engines. There is no edge in the cylinder where the ring turns but I don't know if it means anything. Having come this far I might as well open it up and change all the bearings and the rings while I'm at it.<br />Another observation is that when one piston is at the top and the other at the bottom, I can turn the crank a little without the pistons moving. But with both pistons midway I can't feel any play that way.<br />I also removed the lower unit today and found what looks like a brand new impeller. The oil was chocolate milk colored so I will order a seal kit. Otherwise things seemed OK down there.

 

[Solittle]

Re: Engine rebuild questions, 1980 E25

Why are you opening this motor up?<br /><br />What was the compression?<br /><br />I agree with G Dane that from what you have told us there is little/no reason to disassemble.<br /><br />Do a pressure test to determine where the leak is in the lower unit so you know which seal is leaking. It may be as simple as the vent/fill screw nylon gasket.

 

[R.Johnson]

Re: Engine rebuild questions, 1980 E25

If you take this engine down for a rebuild, do not use any kind of grease for reassembly. Simply use 50-l outboard oil. The only place grease is used, is OMC needle bearing grease. Don't use a substitute here either.No movement of the piston at top, or bottom of the stroke is normal, you are seeing crankshaft over-lap. The bore on your engine is 3.00 in. This can be measured with a dial bore guage, or a telescoping guage, and micrometer. The piston clearance, measured at the bottom of the skirt is .0035 min.-.0065 max.

 

[G DANE]

Re: Engine rebuild questions, 1980 E25

Need for replacing bearings on these motors are rare, except from lower main bearing which should always be replaced if its been off. You will find the roller bearings expensive. Piston clearance at piston top is hard to determine, should be measured at bottom as R Johnson says. Look for cross pattern, when pistons are down. Any visible wear ?? These motors usually runs thousands of hours, if nothing unexpected occurs.

 

[BugEyes]

Re: Engine rebuild questions, 1980 E25

Thank's again for all good advice,<br /><br />The reason I'm tearing it down is a distict knocking noise on idle and low revs that definately shouldn't be there. It comes from the powerhead somewhere and I will never be able to thrust this engine unless I find the cause for it. Also I bought this engine cheap as a winter restoration project, I know nothing about how it's been used or the milage. I'm prepared to spend a couple of $100 to fix it up and I want to do it myself as a learning experience. Guess I'm the kind of person that can't stop myself from messing with mechanical things.<br />Compression is about 100 PSI on both cyls measured with a compression gauge when I pull the rope as hard as I can. So that's not a problem, it's the knock that bothers me.<br />There was a problem with the engine when I bought it that I found and corrected. The problem was that a stopper on the trottle linkage had slipped causing the engine to get excessive preigition timing on lower rews, it wouldn't idle. On this motor there is a direct link from the tower arm to the carb and that was way late related to the turning of the stator plate, that due to the misplaced stopper. I'm concerned what damage could have been made by this as I don't know how long it's been there and if the engine have been used that way.<br />I havn't found any obvious problem soo far but it has to be there somewhere, that sound is just not normal. Gonna open the crankcase next to check everything.<br /><br />Thank's again

 

[umblecumbuz]

Re: Engine rebuild questions, 1980 E25

I havn't found any obvious problem soo far but it has to be there somewhere, that sound is just not normal.

You won't rest until you've stripped every last bit - so go ahead and do it. Nothing to do with mechanics - all to do with peace-of-mind on the water.<br /><br />

With the piston in the top position there is no play but halfway down just around the channels it can be moved sideways a bit.... when one piston is at the top and the other at the bottom, I can turn the crank a little without the pistons moving

All normal - probably nothing to worry about. But the knock and it's possible cause is definitely not normal. Keep stripping! It's good psychology.<br /><br />Ciao

 

[rodbolt]

Re: Engine rebuild questions, 1980 E25

hello<br /> some other tips.if you remove the wristpins for inspection replace the circlips. always use new rodbolts. always replace the bottom bearing.most times the upper,center and rod bearings are fine. carefully clean and inspect them. on reassembly be anal about cleanliness. I use a 3m pad on a drill and alchohol or a spray carb cleaner that leaves no residue. electrical contact cleaner works well too.<br /> if the house warden is not looking a dishwasher is great for cleaning the block . if ya get caught flowers and a dinner out usually helps as well.<br /> I dont use the loquic primer anymore as I am slow sometimes and it will cause the gel-seal to kick very fast. after cleaning use latex gloves . fingerprint oils can hinder sealant adhesion.<br /> other than that is a straight fwd assy. you will need omc adhesive M or its equivalent Gel seal II or its equivalent and omc gasketmaker or its equivalent. replace the crank seals as a matter of course.<br />good luck and keep posting

 

[Solittle]

Re: Engine rebuild questions, 1980 E25

Pike - I had a bunch of fun years back tearing down a 35 to the last screw and was awed when it started on the second or third pull. I do recommend that you get the OMC shop manual.

 

[jy118lfd]

Re: Engine rebuild questions, 1980 E25

if the house warden is not looking a dishwasher is great for cleaning the block <br /><br /><br />Man thats funny! I'm in tears<br />I got caught once using the oven for powder coating. Flowers and dinner werent all I had to do! Lets just say I now have a dedicated powder coating oven

 

[G DANE]

Re: Engine rebuild questions, 1980 E25

If you decide to use the dishwasher, remember to hone and oil the bores right away, they will appear slightly rusty when dried up, I wouldnt do it. Do a search here on rod cap alighment, before you put it together, there is something important there. Torque caps progressively in small steps. Be sure to get the center bearing shell in the right direction or you will get another sound. Also rotate cranck by hand, when you have both cranckshaft halves together, will give you a hint of if something is "talking" Good to see others here from Scandinavia. Good luck

 

[BugEyes]

Re: Engine rebuild questions, 1980 E25

stillfishing;<br />You're right, it's about peace of mind on the water, but also for the fun of exploring the machine.<br /><br />rodbolt;<br />Good advice, but I better stay away from the dishwasher. I hate sleeping on the sofa.<br /><br />SoLittle;<br />I hope to do what you did.<br /><br />G DANE;<br />I better search on rod cap alignment as I don't even know what it means.<br />Where in Denmark are you? I'm in Stockholm and keep the boat in the archipelago 100 km north of Stockholm where we have our summerhouse. I use this boat mostly for fishing and shorter tours with the family.

 

[G DANE]

Re: Engine rebuild questions, 1980 E25

I live in Southern Seeland.

 

[BugEyes]

Re: Engine rebuild questions, 1980 E25

Got one step further tonight and split the crankcase. Took me some headscratching to find the two bolts hidden under the reeds but I got it apart at last.<br />Nothing spectacular in there but one thing caught my curiosity. On the counterweight side of one crank there was an area wich was not sooty like the rest, but clean metal. On the casing, the part that sits under the reeds there were some scratches like something had dragged agaist it, that was also fresh metallic without the slight varnish that the rest had. It didn't look like the crank itself could have touched directly on the goods. Don't know what that could mean if anything. <br />When getting the pistons a little more out of the was I could see some more of the bores. There are some scratches in the bores, only minor but still I can feel them clearly with my fingernail. The bearings that holds the crank to the goods seem good but I have my doubts about the wrist bearings, need to check further.<br />I have not yet seen the sides of the pistons as I didn't have the tool to remove them.<br />What are the screws that holds the cap to the rod? Torx? Anything else?<br /><br />Thank's

 

[G DANE]

Re: Engine rebuild questions, 1980 E25

Its just a 5/16", 12 point socket, get a good one, I've bought a Belzer, they take a lot of torque. If you dont have a manual, I would strongly recommend you to buy one, It will pay for itselves by the mistakes you avoid, and by getting correct torque on everything. You will also need incl tools if you havnt already, or you will ruin something. Biltema has it, maybe even the 12 piont socket. There should be no soot at all in cranckcase. If there is, a cylinder has serious blow by, perhaps missing a ring ?? It can run with very small scores, but that would take a photo to evaluate. Beginning to think you were right about the teardown

 

[G DANE]

Re: Engine rebuild questions, 1980 E25

Concerning the scratches on intake cranckcasinghalf. Are the marks right where the rod end travels ?? If it is, you are maybe standing with a surprise. It probably had a bad rod bearing, and the rodend has touched the cranckcasehalf. If the bearing was replaced without rebuilding or replacing the cranckshaft, its bad. Get that bearing apart first, and post the result. Can you feel any play in the connection rod bearings ?

 

[BugEyes]

Re: Engine rebuild questions, 1980 E25

Thank's DANE,<br /><br />I ordered a manual about a week ago and it's now somewhere between me and Amazon.com and estimated to arrive the coming week. I bought a set of SAE (inch) sockets as sonon as I saw the need, I know what happens if one tries to use metric on SAE or the other way around.<br />The scratches in the casing was to in the bottom at the outer side and could not have been made by the rodend, but something hard have passed trough there and left it's marks. By the look of the screws I don't think this crankcase was ever opened before.<br />I will post pictures when I get everything apart.