Advice to guys with older engines

[DWNewt]

My 1977 75hp Evinrude was running rough. It would die unexpectedly after running good. A few month ago I did a compression test and found all the clyinders around 110. Saturday I did a compression test and got 110 on the top cylinder, 110 on the 3rd cylinder and nothing (0) on the 2nd. I disassembled the engine and found the #2 piston broken on the edge. Enough to see the ring. If any of you guys with older engines have symptoms like these, you probably have a similar problem. Also the lower bearing was missing several ball-bearings. Thanks all you guys who answer our sometimes redundant questions. You've saved me lots of money. BTW, I have to get the head rebored and purchase oversize pistons .040. I've learned how to do it by reading and purchasing a manual. <br />God Bless you.<br /><br />Tech Man

 

[reeldutch]

Re: Advice to guys with older engines

make shure you find the problem that caused all this.<br />carb problem?, oil problem?, timing of?, overheat?,<br />wrong plugs?, wrong octane level?, lugging?,etc,etc.<br /><br />before you put it back in service and dont want to rebuild it within 50hrs find the problem(s) and correct them.<br /><br />good luck

 

[DWNewt]

Re: Advice to guys with older engines

Thanks for the advise, but what is lugging. I just installed a new thermostat. I'll be sure to use a higher octane gas. Just rebuilt the carbs but will recheck the float level because it had a problem flooding. The plugs are according to specs. Not too good with timing but I'll get it checked. <br /><br />Thanks

 

[reeldutch]

Re: Advice to guys with older engines

lugging is when the load is to heavy for the motor.<br />your rpms suffer from the load on the motor and that will result in rapid carbon buildup and sticking rings wich will lead to engine damage.<br />so setup is very important after a rebuild.<br />dont copy the setup before it might been wrong.<br /><br />the octane level is the rate the gasoline is burning inside the combustion chamber.<br />high compresion heads need higher octane to be efficient. the burning rate is faster.<br />high performance engines use the higher octane and even mix it with alcohol or nitro.<br />faster burning rate will cause also more heat.<br />so your best bet would be 87 or 89.<br />tcw 3 oil is a must.<br /><br />good job with the carbs every rebuild needs the carbs done.<br />otherwise its like playing rusian roulette with your motor.<br /><br />also good job with new tstats also put new waterpump kit in. and clean the heads out.<br />take the headcover off and clean all the stuff out. put new gasket on and youl know its clean.<br /><br />sound like your going the right direction.<br /><br />good luck<br />you can set the timing with the joe reeves method.<br />but you have to make shure you verify the timing at wot under load.

 

[rodbolt]

Re: Advice to guys with older engines

actually the higher the octane the slower the burn, which is why most modern motors use 87 octane and some will suffer performance loss with anything above about 93.<br />that motor needs to be able to spin about 5800 or so or it will lug, the piston erosion you describe is normally caused by lugging or a lean carb causing a detonation problem which eats at the piston. can also be caused by an overheat or water ingestion problem. carefully inspect the exhaust divider casting.<br /> water intrusion is also the normal cause of a lower bearing failure on that motor as any water collects at the bottom of the crankcase.<br /> you may wish to bump your main jetting up a couple of numbers as that motor tended to run lean in certain conditions.<br /> when the engine is lugging intake vacum falls off dramaticattly and can create a lean condition as well as the combustion pressure and temp tends to spike leading to detonation which can lead to piston erosion at worst and ring coking at best.<br />either will kill a motor one just takes longer than the other.<br /> check the pressure relief grommets and valves while your in the t-stat housing.<br /> you can hear detonation in your car, most call it valve rattle, you will never hear it on your outboard but the pistons will.<br />your car rarely runs very long at full throttle full load, your outboard can and does for hours.<br />wonder how many nascar motors run with 5 year old t-stats,cooling pumps and last years gas?

 

[Dhadley]

Re: Advice to guys with older engines

Amen Rodbolt.<br /><br />Tech Man, what plugs were you using?

 

[reeldutch]

Re: Advice to guys with older engines

this will explain the octane.<br /> http://auto.howstuffworks.com/question90.htm <br /> http://home.factorypro.com/tech/fuel_octane_vs_power.html <br /><br />good luck