Help 1980s 70hp evenrude Idles but bogs down under load

[N8tureboat]

I just bought a 70hp evenrude that was supposed to run great but after installing it on my boat and trying it out it has a problem. It idles Beautifully and goes in and out of gear great and even accelerates a little bit but when I try to plain out it bogs down. I tried to keep pushing the key in little spurts and I got it to go full out but when I stop pushing the key it slowly slows down and starts to pulse until it stalls.
I tried cleaning the carbs but they where really clean. It free revs great but not under load. Anyone have any ideas or experience with this?

 

[racerone]

Did you find the high speed jets ( orifice plugs ) 3 of them.----You find it in the carburetor bowl way in behind the drain plug.----Water pump impeller changed ?----Compression test results need to be posted.

 

[N8tureboat]

Did you find the high speed jets ( orifice plugs ) 3 of them.----You find it in the carburetor bowl way in behind the drain plug.----Water pump impeller changed ?----Compression test results need to be posted.

The water pump was apparently changed about 2 years ago. It Squirts water really well. I wil check the compression today. I didn’t think it was that because it idles nice and free revs. Someone told me it might be the fuel pump because it’s a diaphragm fuel pump and I don’t think it has been changed in a long time. Got to all of the high speed jets on 2 of the 3 carburetors and cleaned them with carb clean but they looked clean already.

 

[N8tureboat]

The water pump was apparently changed about 2 years ago. It Squirts water really well. I wil check the compression today. I didn’t think it was that because it idles nice and free revs. Someone told me it might be the fuel pump because it’s a diaphragm fuel pump and I don’t think it has been changed in a long time. Got to all of the high speed jets on 2 of the 3 carburetors and cleaned them with carb clean but they looked clean already.

It has a weird home made fuel rail wondering if it was eating too much pressure to feed fuel

 

[racerone]

That fuel rail set-up should work OK.

 

[RBoyd1971]

Could be the fuel pump. Also check the link and sync on the cards and the ignition timing just to rule that out. Also, do all the spark plugs look the same as far as coloration and amount of carbon, etc...

 

[oldboat1]

Don't overlook hull condition on your boat. If it sat out while waiting for repower, there will be water under the floor or soaked into the flotation foam. Once up on plane it apparently runs well -- could have something to do with water weight evenly distributed. Post compression numbers (crank until needle stops, and record result for that cylinder).

 

[N8tureboat]

Could be the fuel pump. Also check the link and sync on the cards and the ignition timing just to rule that out. Also, do all the spark plugs look the same as far as coloration and amount of carbon, etc...

One of the plugs was more dirty than the other. The other 2 where almost clean.
the dirty ones was a normal amount of dirty for a 2 stroke for what I’ve seen before but the other 2 where strangely clean

 

[Keyboardman]

If the plug is clean, then it's not getting any fuel to that cylinder.

 

[RBoyd1971]

Or they are getting steam cleaned from water intrusion from maybe, a leaking head gasket.

 

[racerone]

If there is no spark the plug will stay clean.-------If there is way too much fuel the plug will stay clean.

 

[RBoyd1971]

If it's water getting in there, you'll see it on the plug usually. If no water, what racerone and keyboardman said.

 

[Mblender]

This happened to me when I first put my 48 spl on my boat. Sounds strange but I’m positive your control box has a problem. “ is it hard to get out of neutral or extra slack when it’s in gear?” when it gets to a certain position and starts bogging down and you hit the choke and brings you up to speed it’s because your butterflies on your carbs are wide open but you throttle cable isn’t in time with it.
It could be as simple as greasing your control box or your control cables and readjusting them. They have to be in perfect sync. If your throttle arm has alot of slack and is loose in gear it’s not reaching its max output