85 model Yamaha 70 Hp 70ETLK motor issues

I am asking for some advice.My old motor has worked amazing for a few years now till recently. The issue is random don't happen every time.The motor idles fine but when the motor is asking for more power it acts like it is over loading gas. Put it back on neutral and it idles fine. When it is acting up, some times i can turn the motor off are restart and it acts fine. I have rebuilt the carborators (3) and it was pretty clean. the boat gets used weekly usually. I looked at the water pump and it was bad and needed replaced. I pain Rockwall Marina to replace it and relube the lower unit. I replaced the fuel line from the fuel tank to the motor. It ran good yesterday buy when i went out today it was acting up. I am thinking it is the CDI ( https://www.crowleymarine.com/parts/1373936.cfm ). Rockwall Marina needs six weeks till they can look at it. asking for peoples opinion. I don't mind spending the money if that is what the issue sounds like. Anyone know how to test the CDI?


Thanks

I would clean all of the electrical connections first because the 4 or 5 CDI units I have put on were replacing a no power situation. Not a random malfunction..

Is there a way to test the unit with a volt meter or something like that?

I had a similar problem on my 89 mercury that drove me crazy. After we got the boat back home my son found the fuel line connection was not all the way seated in where it plugged into motor. He pushed connector in till we hear it seat. We had looked at this on the water and no gas was leaking out so we called it good. We got to thinking maybe we were sucking air on acceleration. The next time we went out problem was solved and motor ran great again. Good luck.

I checked the electrical connections. Twisted all then in the connectors. I did not see any type of corrosion.

had similar issues with my 70 hp Yamaha last year. had the carbs cleaned, timing set , cdi changed, nothing fixed it. Turned out to be the rev limiter, may not be that but maybe the place to start, quite a bit less expensive than the CDI.

Well i am seeing that boat motors can be pretty temperamental. I thought old carborated motors would be easier.

except for the intermittent, it sounds like a fuel pump diaphragm rot issue. when's the last time the diaphragm was replaced?

I bought the fuel pump whole assembly from Rockwall Marine roughly two years ago. I removed the fuel in and pumped the bulb. It pumped alot of fuel. I reconnected the fuel pump and disconnected the out to corroborator side and cranked the motor and it seemed to work. I know that under a load is different some times. I was out the lake Saturday after working on it and the boat cranked and ran fine. i went back Sunday and for the first half of the day everything was normal. then when getting ready to head to the boat ramp it started fine but when i was attempting to speed up it bogged down. When it does that you turn the motor off and wait a few seconds and try again. Repeat until it works it took twice. I bought and installed a brand new fuel line from the fuel tank to the motor last week as well.

we can check it out need to bring in next Monday

What is your rate?

I dont want to dump alot of money into this motor. I have a 2015 motor that if it is a major issue i want to put on the pontoon.

Madatu if you decide to go with the newer motor on you pontoon I may be interested in buying your 70 horse if the compression is good on all three cylinders