Recently purchased a 1978 Sea Sprite with a 1978 70 hp Evinrude. Ran nice the first trip but noted that throttle response was slugglish from low idle to wide open. Would periodically die out when transitioning through this mid range speed. Any suggestions on this issue once I get the second bigger issue resolved noted below.
Second issue noted during second trip. Same symptoms as above but died out and couldn't get restarted. Pulled plugs and noted water in cyl #3. Turned it over an water misted out #3 plug hole. Checked compression on all 3 cylinders. All rock solid at 110 psig. Thinking head gasket at this point but havent opened it up to check the cylinder or head. Looking for some advise and confirmation Im on the right track. Is there anything that Im leaving out. Pretty new to the outboard thing, also wondering how difficult to tear this thing down. I would appreciate any help!!
highly recommend the factory shop manual, available at kencook.com or marineengine.com - nothing tricky about the cylinder head.
Three fixed jets in the carbs. That engine will idle on two cylinders and sound perfectly happy doing so - till you put a load on it. If the head gasket don't fix your sluggishness, a carb rebuild will. Heck, might as well do it now anyway, they always seem happier with a good carb cleaning.
If you don't know when the water pump impeller was last changed, I'd do that now, too.
welcome to iboats!
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Thanks jtexas. The site is awesome. I was just looking into the manual locally here in Green Bay but will check out the sites you referenced. Good call on the carbs and I have been reading several recommendations on the impellar.
Another quick question. I have also been reading that the exhaust plate gasket could allow water into the cylinder. Does having good even compression on all cylinders around 110psig help differentiate between a cylinder head or exhaust plate gasket?
By the way, you described the idling fine then bogging scenerio perfectly. Confirms to me that this motor was never firing on all three. Thanks again bro
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Forget the carbs and everything else for right now. It is absolutely critical that you get that water leak fixed. It will destroy the bearings in the crankcase. If they aren't already. Rust happens to polished steel very quickly.
If it is not the head gasket it is the exhaust cover. Probably the exhaust cover. (Naturally, that is the hardest to get to!) Those inner covers will warp at the slightest bit of overheating, and then water squirts into the exhaust ports. There is lousy support for the cover around the ports. You have to replace the warped cover and gaskets.
ditto with fr,the exhust plates were chronic problem causing omc to change in later yrs ,ther are multiple plates and gaskets,your comp is great ,leaving the head gasket to likely not be suspect,and you running issues may get better when water intrusion is dealt with,i suggest you also spray some oil in the cylinders for protection while you fix problem
Thanks Mikesea and FR. Im on it. Going to tear into the exhaust gaskets next week and noticed this am that there are several...cover, a larger plate and smaller one. I will check for trueness when its opened up.
I sprayed some W-D 40 down the leaky cylinder. Will that do it for a week until I get to it or should I fog it with something else to prevent rusting.
Hey guys. Just wanted to give you a quick update and thank everyone for the help. The exhaust plate gaskets were definately the problem. Big holes and lots of water in #3 and actually in #2. Im surprised this thing actually ran. I got curious at this point and pulled the head. Head gasket was in pretty rough shape as well. It had good compression by was leaking down pretty good. Took the kids out tubing over the Labor Day weekend and the old 70 ran like a top. Sooooo Im back in business. Thanks again. This site is awesome.
70 hp Evinrude water in cylinder 3
Re: 70 hp Evinrude water in cylinder 3
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