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1973 evinrude 65hp power issues

M

mmr

New member
So I have had my boat out on the water several times this year with no issues. But last weekend when I put her on the water it started a little hard and when I throttled up and it sounded great for about 15 seconds then it lost power. If I pull out the choke it the rpms come up but still not to full throttle or full power. So I took it out of the water and on the driveway with the water muffs on it runs spectacular no issues whatsoever. My thinking is that somewhere in the fuel lines it got plugged. I took the carbs off and didn't see any debris in them. Any suggestions would be helpful. The motor is a 1973 65hp evanrude triumph.
 
There is no load on it in the driveway, so that is a meaningless test. It probably is not running on all 3 cylinders. Check spark on all and don't just assume the spark plugs are ok. Let's hope the problem isn't the one that kills the 65hp---water getting into cylinder from a warped exhaust cover.
 
I know it has spark on all 3 I already checked that. Any other suggestions or things I should be looking at?
 
They all roar and sound good on a hose to the untrained ear.----------------Start with a compression test.------------Are all carburetor / ignition linkages in place ?----------All 3 carburetors go to full open ?--------------Does bulb go hard when you prime / fill the carburetors ?
 
Everything sounds great when running on the hose in the driveway all throttle plates open up good and all linkages are in good shape and in place. How can I check if water is getting into the cylinders through the exhaust cover? What will the signs be for that? I have a pretty decent mechanical background as I am a small engine 2 stroke mechanic but this is a bit different than a string trimmer
 
One of your statements..... "If I pull out the choke it the rpms come up but still not to full throttle."

That indicates that the carburetors have become fouled due to sitting (a common problem). Remove, clean, and rebuild them. Be sure to carefully clean the high speed jets with a piece of single strand steel wire as solvent just doesn't do that job properly.

The HS jets are located horizontally in the bottom center portion of the float chambers.
 
I have cleaned the carbs and it made no difference. The Jets were clean with no debris in them the only things I can think of is 1 the fuel supply is restricted or 2 the float height in carbs is off causing a fuel supply issue?
 
If you have proper compression and spark that will jump a 7/16" gap with a strong blue lightning like flame... a real SNAP, that leaves the carburetors. Both compression and spark are worth double checking.

I assume you've removed the carburetor drain screw plugs to see if fuel is actually filling the float chambers?

Possibly debris within a fuel line has clogged one of those cleaned high speed jets?

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.
 
??---------What if one cylinder had lots of spark but no crankcase compression ?-------No cylinder compression ?-----No fuel going into it ?--------And have you checked the flywheel key ?---------------Testing and trouble shooting beats guess work every time.
 
So I did a compression test on all cylinders and I have no compression on the top cylinder, 110 psi on the middle and 100 psi on the bottom. I also noticed what may have been some water droplets on the spark plug of the top cylinder as well.
 
Does that mean the cylinder head gasket is blown ant it's allowing the water from the engine cooling system into the cylinder?
 
Pull the head it should be obvious may as well order a head gasket now they are relatively cheap and you will have less down time! Then look at the cylinder walls for scoring especially on the exhaust side.
 
Do you know how old the thermostat is? While the head is off pull the thermostat cover and inspect the pop off valve and spring if the spring is getting weak just replace it as well as put in a new thermostat and you can get the new parts all at once.
 
So I replaced the head gasket and put the boat back in the water today (4th of july) and test ran it. It ran great for 20 min or so and then it started acting up again. Pulled it out of the water and re ran compression checks on all cylinders. All cylinders have roughly 100 psi of compression and all plugs have spark, however now the middle cylinder has water in it any thoughts as to the cause of that?
 
Look at post # 2 again.-------Gives you a strong hint.-------And I know that all older outboard cylinder heads are warped, including yours.------Did you check it / resurface it ?
 
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