'83 evinrude 70 hp loses power

E70elcte

K well,
This is what happens.

I'll run around low throttle for about an hour everything's fine.
10 min of running full throttle and it cuts down to very little power instantly
Just enough to make it back in. I will say that it did seem to run rather rough
The motor doesn't feel hot though
Lots of water flow
I get home an hr later and it starts instantly and will rev up instantly

I think it's the temperature sensor.
My friend was once an outboard merc mechanic and pointed me in this direction
I got in late today and plan to ground out the temp sensor wiring to listen for a warning siren
Though I'm not entirely sure that there is one on my throttle

What I'm really interested in is "slow mode" I've been reading lots of threads and this is a common issue
Would a faulty temp sensor put my outboard in slow mode?

Impeller was done, leg was serviced, carbs were cleaned, new spark plugs. Fuel system does not seem to be the issue. Runs fine until I run her full blast for ten minutes
Any ideas would be greatly appreciated.

Re: '83 evinrude 70 hp loses power

That mtr didn't have SLOW. Sounds more like you have ignition probs. Do a cyl drop test on it when the prob occurs and see if you can find a dead cyl or two.

Re: '83 evinrude 70 hp loses power

boobie said:

That mtr didn't have SLOW. Sounds more like you have ignition probs. Do a cyl drop test on it when the prob occurs and see if you can find a dead cyl or two.

Click to expand...

Ok We'll I'm going out this weekend then. Should I bring tools to switch coils around to eliminate that? If that doesn't affect it I should try an ohms test on the stator while its buggered? I understand that's another part that can become inoperative when hot if there's a problem with it.

Re: '83 evinrude 70 hp loses power

Could also be a powerpack, which would affect the cylinder firing (ignition as stated in post above). Do a search, there are some tests you can do to narrow it down.

Re: '83 evinrude 70 hp loses power

Agree. Could be you are losing spark to one cyl. Weak ignition components tend to fail once the engine heats up to normal operating temps. Take an inductive timing light out with you next time you go boating. When the engine seems to slow down, put an inductive timing light on each plugwire and check for spark while the engine is idling in gear. The flashes from the gun will show misfires, intermittents, etc. Easiest to eliminate the ignition problem first. If the spark checks out ok, look at your fuel system.

Re: '83 evinrude 70 hp loses power

Check your wire connections, especially those stupid plug/clip connectors. Took me almost 2 months to figure out an issue once and that was it.

Tom B.
(LongLine)

Re: '83 evinrude 70 hp loses power

Timing light showed no signs of an erratic spark. Going over all connections revealed no problems. I opened the fuel pump and the diaphragm looked pretty decrepit so I redid that. I also installed a tach so as to help further diagnose things if anything changes. Does anybody happen to know the max operating rpm on this motor?