Old Evinrude 70 Hp - Hard to start when hot, loses power and stalls

hamo

Recruit
Joined
Apr 3, 2004
Messages
3
I got stuck at sea yesterday and had to get towed in. Here is a synopsis of the situation.<br /><br />We went 10km and then had to stop for 5 mins (which turned out to be 2 hours!) The motor ran fine all the way out but would not restart. On the previous run we had loss of power under load which led to stalling. We were able to restart but only after many attempts<br /><br />Some history<br /><br />1. Problems started after I closed vent on fuel tank (didn’t know about this - and still don't know what difference it makes)<br />2. At the same time I put a spacer on the end of the propeller (which I doubt would have any impact)<br />3. First probs were losing power when under load and then eventually stalling. This was intermittment. To solve it I would stop the motor and restart. It blew a lot of smoke but then ran fine.<br />4. Restarting was difficult on these occasions. Often took a long time and when it did fire it blew a lot of smoke.<br />5. Motor has started reasonably well when cold, however the last few times it has been a bit more tricky<br />6. It has new spark plugs<br />7. Fuel is about a week old and mix is good<br /><br />Any ideas???
 

Xcusme

Commander
Joined
Apr 21, 2003
Messages
2,888
Re: Old Evinrude 70 Hp - Hard to start when hot, loses power and stalls

Hamo,<br />Welcome to Iboats!<br />To answer your #1 question. What difference does venting the fuel tank make??Remember, the fuel pump draws fuel from the tank by suction, air must be allowed to equalize the pressure in the tank. If the tank is sealed, the fuel pump will draw a vacuum on the tank, which will, at some point, stop all fuel from flowing. By venting the tank, the pump can draw fuel and pump it to the carbs. Fuel starvation can cause the loss of power and stalling that you describe.
 

hamo

Recruit
Joined
Apr 3, 2004
Messages
3
Re: Old Evinrude 70 Hp - Hard to start when hot, loses power and stalls

Thanks! That does make good sense and I can see how it contributed to the initial loss of power / stalling.<br /><br />I'm wondering now about the failure to start when hot. Vapor lock is something I read about but don't know much about - could that be an issue?<br /><br />Could that be a product of a closed vent at all?<br /><br />Of course today the boat started first time every time in the driveway...
 
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