Lost some compression. Update. Pictures now on.

[steviecops]

Re: Lost some compression. Update. Pictures now on.

Hi G DANE<br />I have a spare head that I bought a while back, (I've been building up a stock of spare parts as and when they come up), but a piston would be good if he has one. I might take the block in to see whether it needs boring first though. The scoring is very slight and the compression is still good at 130 in the bad cylinder and 150 in the top. I might be lucky and get away with just honing. Is there likely to be any damage to either of the ports?<br /><br />Anyway, I've got the new 50 hp powerhead all dressed now and I'll be putting it on tomorrow. Will I need to set the timing again? I took care not to move anything when I swapped the parts over. Also, what fuel mix is recommended for running in? My OEM manual says use 50:1.<br /><br />Thanks<br />Steve

 

[G DANE]

Re: Lost some compression. Update. Pictures now on.

The ring might have hit the port edges.

 

[steviecops]

Re: Lost some compression. Update. Pictures now on.

Hi<br />Well my motor is alive again. Got the new powerhead on it and it sounds smooooth and sweet. Can't wait until it's broke in.<br /><br />Turns out the damage wasn't done by a broke ring, but a broke rod bearing! When I took my old powerhead apart the bearing cage fell to pieces. All the rollers were there, but the cage was destroyed and a few little bits were missing, (well not actually missing, I found then embedded in the top of the piston!). The cage and rollers were still in position under the cap, but just fell apart when I took the piston out.<br /><br />My question now is, what would have made that rod bearing destroy itself, and how do I prevent it happening again? There was very little, if any carbon build up in that engine. There was no carbon behind the piston rings at all. There is some slight damage to the crankshaft. I'm not sure if it is old damage or whether the rod bearing did it when it broke. <br /><br />I've added some more pictures documenting the ordeal. By looking at the pictures, can this crankshaft be salvaged?<br /><br />more pictures <br /><br />I'd appreciate any advice on the cause of the bearing breaking, and on whether I can do anything with the crankshaft. Don't know if it's connected but I had to make some radical changes to the settings for the timing when I put the new powerhead on. Starting from scratch I followed the manual step by step and had to adjust the idle screw and the advance screw quite a bit. Could my motor have been running good with the timing way off? Could that be what destroyed the bearing?<br /><br />Thanks<br />Steve

 

[pj_elia]

Re: Lost some compression. Update. Pictures now on.

Can't access pictures, it asks for a login name.

 

[steviecops]

Re: Lost some compression. Update. Pictures now on.

Bloody AOL! <br /><br />Does anyone know how I can post pictures on here?<br /><br />Thanks<br />Steve

 

[dolluper]

Re: Lost some compression. Update. Pictures now on.

Try photobucket

 

[steviecops]

Re: Lost some compression. Update. Pictures now on.

Hi<br />Thanks for the advice. I've used photobucket and the pictures should now be on here. <br /><br /> pictures<br /> <br />Any advice on the cause and damage to crank?<br /><br />Thanks<br />Steve

 

[stan_deezy]

Re: Lost some compression. Update. Pictures now on.

stevie: pictures are still password protected unfortunately <br /><br />what oil ratio were you running originally?<br /><br /><br />oh and when did you last check the timing on the 55?

 

[steviecops]

Re: Lost some compression. Update. Pictures now on.

O.K thanks Stan, I think I've managed to unprotect them now.<br /><br />I was running the 55 on 50:1. I never actually checked or changed the timing on the 55 since I bought it, although I did do a link and synch a few times after I'd rebuilt the carbs, etc. When I set the timing from scratch on the new powerhead, I had to make quite a bit of adjustment on the timing screws so it's possible that the timing was wrong originally. But would the engine have run so well if the timing was off?

 

[stan_deezy]

Re: Lost some compression. Update. Pictures now on.

Steve, I can only go on the experience I had when I ran a mariner for several months and then checked the timing <br />The timing on that engine was out by 17' but was running not too bad at all: in fact it started a lot better <br />I'm wondering if the timing was screwed a bit and maybe causing predetonation but you say the plugs were pretty carboned up, so that's unlikely: if she was too advanced she's have overheated the plugs and done it evenly. Maybe just a manufacturing defect?

 

[sprouticus]

Re: Lost some compression. Update. Pictures now on.

the same thing happened to my 1977 70hp rude a few months ago. I ended up scrapping the motor and buying another one. If anyone needs a bottom end or other parts for this motor contact me.....they're free. I am very curious as to what the cause was myself, as I do not want it to happen again.

 

[steviecops]

Re: Lost some compression. Update. Pictures now on.

It is slightly worrying not knowing what caused the bearing to break up like that. Most engine failures that I've read about have been caused by running lean, over heating or excessive carbon. Non of these things apply to my engine.<br /><br />The damage to the crankshaft looks more like pitting than anything the bearing did. Maybe the pitting caused excessive vibration around the bearing and led to it breaking up? But what caused the pitting to the crankshaft? Maybe it's as Stan says, a manufacturing defect?<br /><br />I'm sure Dhadley, Joe Reeves, etc, have seen many broken bearings and may know what the common cause is.<br /><br />Thanks<br />Steve

 

[rodbolt]

Re: Lost some compression. Update. Pictures now on.

those pits are water marks. caused by corrosion. the bearing surface will pit up and then get polished but the danage was done long before it finally died. usually caused by a bad lower crank seal or a exhaust divider leak. its quite common around here.

 

[G DANE]

Re: Lost some compression. Update. Pictures now on.

The cranck looks exactly like a 35 I had apart once. It took a swim, was recovered and ran for years after. No damage to cylinders, as they were flushed out and oiled immediately, but it sat for a period of time untill they got it fixed. Rollers leave rust marks on cranck journal, and when they run damage gets slowly worse. Your flywheel teeths look rusty on photo, it could have been from leaving motor out without hood, but could also be salt water. This is why a motor has to be run immediately after, or disassembled within hours. The broken cage is rare, will cause rollers to tough eachother.

 

[steviecops]

Re: Lost some compression. Update. Pictures now on.

Thanks for the info.<br />It's interesting getting a picture of what may have happened to the engine before I got it. The main thing is, the damage was probably done before I got the motor and it isn't anything I've done that's caused it.<br /><br />Is there anything that can be done with that crankshaft, or is it just fit for the bin?<br /><br />Thanks<br />Steve

 

[billaranguren@yahoo.com]

Re: Lost some compression. Update. Pictures now on.

I had the same bearing problem in my old 55.<br />BAD design. Easy to install at the factory. Notice the replacement has no cage, just needles and end washers. A few years after the 55 problem I stripped down a 175. Bearings were intact, but a couple cages had hairline cracks. Replaced them all.

 

[rodbolt]

Re: Lost some compression. Update. Pictures now on.

there are some places in the states that repair cranks for outboards . the new style bearings have heavier duty cages. a friend of mine made a fixture to replace the rollers in the new style cage but I just buy the bearing assy.

 

[steviecops]

Re: Lost some compression. Update. Pictures now on.

I've heard of auto crankshafts being reground, but don't know if they can do that with an outboard crank. Can you buy different bearings for reground crankshafts?

 

[G DANE]

Re: Lost some compression. Update. Pictures now on.

There are companyes that recover cranckshaft journals - even here en Denmark. Ask an automotive cylinder shop for a name and telephone number. A Google search for Cranckshaft Repair returns lots of hits. As I guess you are in no hurry, look for a c/s on ebay now and then.

 

[wilde1j]

Re: Lost some compression. Update. Pictures now on.

steviecops, you're running 25:1 oil for breakin, right?<br /><br />Bearings are the same size for reworked cranks. They add weld mat'l to bad spots, then regring to original diameter spec.