Evinrude 40hp big twin

[Fisher freak]

i have recenty bought a 40hp big twin. the guy i bought it from said it was 1970s era. how do i find out and what might i look for if their are any common problems? every reply will help this is my first boat and motor so it is still a fresh concept for me.

 

[Tyty]

Re: Evinrude 40hp big twin

Well for starters you should check the lower unit lube and make sure its not milky rub a little bit of the lube with your fingers as it comes out you shouldnt feel any grit it should be just oil and there should not be any water. I would check the spark to you can have someone crank it while u hold the plug with it touching the metal cover so its grounded it should have a nice blue spark. You should make sure it has good compresion with a compresion gauge.

 

[Fisher freak]

Re: Evinrude 40hp big twin

i have done a commpressin test and checked the spark both are good. should their be a serial number on this year of motor?

 

[rodbolt]

Re: Evinrude 40hp big twin

other than the above I would change the water pump and thermostat and make sure all the water pressure control parts were still in head.
good motors. motor mounts liked to break and most are NLA,they dont tolerate overheats at all and there are no warning systems for it.
points are a pain to maintain but as long as the stator plate bushing is ok they work.

 

[Intermediate Mariner]

Re: Evinrude 40hp big twin

Keep an eye on the bottom cylinder. Call me crazy but I have seen alot of guys with bad bottom cylinders.?!?!.. (Mine was too - don't know if overheated or debris in cylinder but tore up the piston).

I always pull the head right away to resurface plus get to inspect cylinders for grooves, carbon build-up etc and check out water passages for calcium build-up.

Also I agree with Tyty on lower unit - if the oil does not come out right away you may be in trouble... if grit/water/milky comes out you ARE in trouble and will most-likely have some rusted gears but muriatic acid clean 'em right up like new (or pits them if rust is too deep). Also DON'T put any aluminum in muriatic acid!

Rebuild Carb and Fuel Pump and replace all hoses (ESPECIALLY the bulb - they deteriorate from the inside and the black rubber gummy suff clogs up everything and it wont start) and any broken wires (which will be corroded).

 

[Fisher freak]

Re: Evinrude 40hp big twin

Thanks i do need to change the fuel hose it is dry and tough so its gone