1988 70 evinrude rebuild questions

[J JACKSON]

I am in the process of rebuilding my powerhead, the #1 rod bearing went and scored the cylinder too. I am not really sure what caused it. The engine ran hot last time out but only for about 1 min (just enough time to get out of the channel once the alarm came on) and i found a piece if the lower screen stuck in the thermostat. After removing it ran fine but had a rattle. so we ran at low speeds to the ramp.
It also has VRO and the other connecting rods are discolored but no damage to the crank other than slight bluing. But a inop VRO would have gotten all the bearing not one, I have dissembled the carbs and don't see anything blocking the main jet.

Next question can the crankshafts in these engines be polished? i measured the journals and it measures well within spec. I have built many racing engines and small engines just no outboards.

I am going to do away with the VRO and relocate the tail tell to the top of the head are there any other updates i need to do?
I saw something about a updated thermostat but i can't find it now best i can remember if it is white it needs replaced with a black one.
Almost forgot the engine data :E70ELCCA s/n G1800349
Thanks for any help and ideas

 

[multimech]

Re: 1988 70 evinrude rebuild questions

The VRO being bad would not necessarily take out the entire set of bearings in my opinion, besides you should have a no oil alarm working on the engine that monitors that. There are bleeds specifically on the engine that also help lubricate the engine. A blocked check valve in any of these bleeds could starve a component for oil, like your rod for example. Although, an overheat can expand pistons out very quickly and all they need to do is make contact with the cylinder walls to either seize or cause damage to both the piston and the rod.

2 stroke cranks are very hard and can be polished to clean them up, especially the slight blueing you have going on. Keep the polishing to a minimum to clean up the effected areas. Although it might not be a bad idea after the crank is polished up successfully, to put the crank in a set of V blocks and make sure it is true.

 

[J JACKSON]

Re: 1988 70 evinrude rebuild questions

i was going to have the machine shop i use polish the crank when they bore the block, so it will be done on a lathe, what are these bleeds you are talking about? the holes in the connecting rods the feed the bearings?

 

[bonz_d]

Re: 1988 70 evinrude rebuild questions

Very interesting, I have a 1988 70hp also that I have been debating a rebuild on. It is in need of a crankshaft as the splines were wiped out of it. May have to locate a manual for this as I was unaware of the "bleeds" on this for the lubrication.

 

[J JACKSON]

Re: 1988 70 evinrude rebuild questions

anyone know about the thermostats?

 

[bonz_d]

Re: 1988 70 evinrude rebuild questions

Thought I read something about this posted by chinewalker. Might want to search his posts on rebuilds.

 

[Chinewalker]

Re: 1988 70 evinrude rebuild questions

I fuddled around with the thermostats on one of these last spring before I found out someone had replaced the head with a later one that used a different housing, etc. Once I got the correct head on the motor, along with the recommended thermostat, it ran beautifully. With the later head the thermostat I had on it never opened or closed anything and the motor ran ice cold, wouldn't idle for *@^& and stalled repeatedly. With the correct head and t-stat combo, it idled all day and didn't stall at all. I did the other cooling updates, too (moving p-tube and adding updated spring).