Top End Problems (70hp Evinrude)

[Meghan]

I recently purchased a late 70's (early 80's?) 70hp Evinrude. I've rebuilt 3 carbs as well as the fuel pump - and the motor still has no top end. It only reaches 3000rpm in the water (occasionally jumps to 3500 - 4000rpm). It seems to be bogging down and picking up by itself...does anyone have any ideas on what could be causing this?
Thanks!

 

[jimdd810]

Re: Top End Problems (70hp Evinrude)

do a compression test. Are you sure your firing on all cylinders. Are you sure the carbs are completley clean?

 

[Meghan]

Re: Top End Problems (70hp Evinrude)

I had a compression test done and the carbs rebuilt.. Just picked it up from the shop today - and that still hasn't fixed the problem. I'm not 100% on whether it's firing on all 3..but I'm assuming the mechanic would have figured that out? I will definitely look into that though - Any other ideas on what my problem could be if that doesn't seem to be the case? Any advice would be appreciated

 

[Dave64]

Re: Top End Problems (70hp Evinrude)

I had a compression test done and the carbs rebuilt.. Just picked it up from the shop today - and that still hasn't fixed the problem. I'm not 100% on whether it's firing on all 3..but I'm assuming the mechanic would have figured that out? I will definitely look into that though - Any other ideas on what my problem could be if that doesn't seem to be the case? Any advice would be appreciated

I have a 1981 70 hp Evinrude,here's what I when through. Discovered that the middle cylinder was'nt firing. Traced that problem down to the power pack and replaced it. After getting all 3 cylindeers to fire it still had no top end!! While taking the spark plugs out noticed that they had water on them.Pulled the water jacket and the head, all three cylinders had water in them. The good part was the head was not cracked. Replaced all gaskets and so far it runs like scalded dog!! So check for water in cylinders, pull the spark plugs and look in the hole, if the end of the piston is bright an shiny you could have water in the cylinders. Good luck.

 

[tashasdaddy]

Re: Top End Problems (70hp Evinrude)

Just picked it up from the shop today. take it back to them, they did not fix it, as they said they did.

 

[Meghan]

Re: Top End Problems (70hp Evinrude)

Thanks for the advice! I will check for water in the cylinders this afternoon and see if that could be my problem! Appreciate the advice!

 

[Meghan]

Re: Top End Problems (70hp Evinrude)

hey do you no what the compression is supposed to be on late 70 early 80 70hp evinrude

 

[jimdd810]

Re: Top End Problems (70hp Evinrude)

Meghan,
I would highly recommend you bring that motor right back to where you got it worked on. Any mechanic worth his salt will find the problem and make sure its fixed with out charging you. I am a mechanic and I own my own shop. I would not be in business for long if I worked on motors and charged customers and their motors didnt run right when leaving my shop. IMHO

 

[Meghan]

Re: Top End Problems (70hp Evinrude)

Okay, I've checked all three cylinders for water...no water...top cylinder spark plug was clean. Looked brand new. Middle cylinder was black as well as spark plug, bottom cylinder was black, as well as spark plug. Checked spark on all plugs and all three have spark. What should the continuity be on spark plug wires as well as coils? Or does anyone have any other ideas on what my problem could be? Thanks in advance for the advice!

 

[Meghan]

Re: Top End Problems (70hp Evinrude)

also when running my motor out of the water with the muffs on i could hear what sounded to be a miss fire any clues?thanx

 

[Haffiman]

Re: Top End Problems (70hp Evinrude)

Testing problems on muffs without proper back pressure is a dead end.
From your plug status, it may be that your cyl# runs lean.
Why, is another thing.
High temp? Low water pump capacity, defective thermostat leaving an air-pocket on top)
Missing ignition pulses?
Upper carb partly blocked or low fuel pressure not filling it properly. low float setting...?
How is the compression balance between the cylinders?(is upper low compared to the others?)

 

[Dave64]

Re: Top End Problems (70hp Evinrude)

also when running my motor out of the water with the muffs on i could hear what sounded to be a miss fire any clues?thanx

Hey guy, Did you ever get that 70 hp evinrude running???

 

[Meghan]

Re: Top End Problems (70hp Evinrude)

hey i was woundering if any one could tell me the model of my 70hp evinrude all i have is the serial number c7174178 i cant read the model number anymore

 

[Meghan]

Re: Top End Problems (70hp Evinrude)

Hey guy, Did you ever get that 70 hp evinrude running???

I had it out Sunday..it did 3000rpms all day we were fishing..right before we loaded er up..I took it for one last spin and she hit 5000rpm! Still haven't had the time (and I can't read the model #) to order a repair manual...I changed the spark plug wires - but it still sounds like it has a miss... Hoping someone will have that model # so I can get a repair manual