1960 big twin 40 cooling system?

[nahoo7]

Water comes out of the exhaust hole at idle not a lot but compatible to clips on utube.took it out to adjust high speed needle after running wot for 5 mins looked at tell tale port and only steam was coming out.shut motor down waited 2 mins started up again and water was coming out again is this normal, how much water normally comes out at wot.I took the boat home removed lower unit stuck hose on 1 water tube and it came out the other tube.Does most of the water exit through the lower exhaust port below
the water line just dont want to overheat the motor and not sure how cooling system works cheers.

 

[HighTrim]

Re: 1960 big twin 40 cooling system?

Is the t stat and valve installed?

 

[racerone]

Re: 1960 big twin 40 cooling system?

That is hot water and vapour, not steam.----------That is the way the cooling system operates on the 40 HP model.---I water skied many miles behind a 40 HP and water pours out that exhaust tube up top.-----Then settles down to a mist at idle.-------If you do not know how old the impeller is then you should put a new one in.

 

[nahoo7]

Re: 1960 big twin 40 cooling system?

Yes the t stat and valve is installed and the impeller looked in good condition but no idea how long it has been installed thanks for your replies.

 

[nahoo7]

Re: 1960 big twin 40 cooling system?

Another question when I connected the hose to either water tube no water came out of the tell tale exhaust hole.water did come out when the motor was put back together and idling though .why is that?

 

[racerone]

Re: 1960 big twin 40 cooling system?

That water comes out with the exhaust.-----Therefor when motor is not running there is no water there.----------That motor was quite well built and all you need to do is put a new impeller in every 5 years or so.--When you looked at the impeller were the vanes curved or nearly straight ?

 

[kfa4303]

Re: 1960 big twin 40 cooling system?

Actually, you need to put in a new impeller at the start of EVERY season. NEVER wait 5 years in between. Make sure the lower unit is always well submerged in water when running as well. The water level should be about 1" - 2" below the main exhaust port on the back of the motor. Be sure the thermostat is properly installed as well. You can get a new impeller and t-stat right her at iboats for about $20 each. Here are some handy links.

Reviving a Vintage Big Twin - Part 1

1960 Evinrude 35520 40 hp Outboard Motor Parts

 

[racerone]

Re: 1960 big twin 40 cooling system?

The factory 40 HP impeller is quite durable and every 5 years is good.----------------Running in ice cold water then maybe every year !---Water level about 5" above the pump is fine.-----------No need to have it 1" below the idle exhaust relief !

 

[kfa4303]

Re: 1960 big twin 40 cooling system?

The water temperature is irrelevant. It's the tips of the fins that become worn and/or our of alignment with use, which cause the impeller to fail, or work less efficiently. Besides, a new impeller every season is cheap insurance against catastrophic failure. Plus, it gives you a chance to inspect the lower unit. You're right about the water level. It only need to be that high when running in a test tank. While mounted on the transom be sure that the anti-vent plate is level, or slightly higher than the keel.

 

[racerone]

Re: 1960 big twin 40 cooling system?

The water temperature does matter as rubber becomes stiffer with a drop in temperature !----Rubber does not flex as easily when cold.----At full throttle the tip of the vanes does does not touch the pump housing.

 

[nahoo7]

Re: 1960 big twin 40 cooling system?

Ok will check impeller again, when I remove the impeller from the housing are the vanes meant to straighten out again to indicate it is okay?

 

[racerone]

Re: 1960 big twin 40 cooling system?

If the impeller is fairly new they will go straight.-Vanes on an old impeller will take a " set " with age.---Impellers with vanes that stay curved do not work properly.

 

[HighTrim]

Re: 1960 big twin 40 cooling system?

If using OEM impellers every 4 to 5 years is fine. I have pulled some out that still looked good, but if I drop a gearcase a new impeller is going in, especially if it has been a few years.

Aftermarket impellers are a different animal. Some need changing every week

 

[nahoo7]

Re: 1960 big twin 40 cooling system?

Ok cheers racerone.

 

[nahoo7]

Re: 1960 big twin 40 cooling system?

Ok when checking the impeller the housing that fits over the impeller is plastic I think and very rough to touch is their supposed to be an aluminium cup in there if so I am missing that which probably is causing the loss of water pressure?

 

[racerone]

Re: 1960 big twin 40 cooling system?

If it is plastic then it is a newer factory replacement.-------What I do is remachine the aluminum housing so I have never installed the new type.---------Post pictures to make it clear.

 

[kfa4303]

Re: 1960 big twin 40 cooling system?

Of course the tips of the impeller touch the walls of the housing. How do you think they become worn? If someone has installed an aftermarket impeller housing, there's no tell what else they may have done, which is even more reason to replace the impeller. Don't be cheap and lazy. Get a new impeller! At the very least the rubber will become, dry, rigid, distorted and inflexible due to lack of use and sitting idle over half the year in your area and/or the fins themselves will become misaligned within the housing thus hampering its performance. You will NEVER see a manual suggest waiting 5 years between water pump changes either, never. Don't be penny wise and pound foolish.

 

[racerone]

Re: 1960 big twin 40 cooling system?

At full throttle the tips do not touch the outside of the housing !

 

[nahoo7]

Re: 1960 big twin 40 cooling system?

Actually the impeller is not dry and hard the fins are flexible and when removed only slightly bent I get good flow at idle in tank it is at full throttle on the water the flow stops.it is not the cost of the impeller I think there are other issues involved here.in queensland australia boats are used all year round rare for them to sit for over 6 months.

 

[F_R]

Re: 1960 big twin 40 cooling system?

Ok when checking the impeller the housing that fits over the impeller is plastic I think and very rough to touch is their supposed to be an aluminium cup in there if so I am missing that which probably is causing the loss of water pressure?

Really? I didn't know they ever made a plastic housing for that motor. I suppose I could be wrong.