Hesitation during plane-off

[melbournegreg]

I have an older 3 cylinder 70HP Johnson (VRO removed) that has begun to have significant hesitation when trying to get the boat up onto plane. The low rpm seems fine and the engine runs fine at high rpm if we manage to get there. The hesitation sounds cyclic and usually prevents getting up onto plane. Removing/cleaning the spark plugs solves the problem only temporarily (1-2 plane offs).<br />Anyone have ideas?

 

[DJ]

Re: Hesitation during plane-off

Your carburetors are in need of attention. (rebuilding).<br /><br />Make sure the sync & link adjustments are correct. You'll need a manual to do it.

 

[melbournegreg]

Re: Hesitation during plane-off

Thanks. My family and I would really like to get this working again. I just purchased the boat and only had 3 successful outings prior to this problem. The motor is 1988.<br /><br />I wondered if you might consider looking elsewhere for this problem...<br />1. What are the recommended spark plugs and gap?<br /> <br />2. Can the carbs be cleaned without a rebuild kit?<br /><br />3. Should I replace the fuel filter and/or fuel pump? (we siphoned out the old fuel and never used any it but it looked rich even though the previous owner had been using the VRO).<br /><br />4. Is an online version of the manual available to help with the sync & link adjustment and the fuel filter installation?<br /><br />Thanks,<br />Gregg

 

[craigvalk]

Re: Hesitation during plane-off

Greg, I can make a couple suggestions but can't answer all.<br />Most likely you need the rebuild kit.. they are cheap, and it's likely you will tear gaskets and stuff when you disassemble a carb. Don't take shortcuts and you won't have to do the job twice.<br />Outboard carbs are famous for getting gummed up, mostly from being left sitting with fuel in them.<br /><br />A fuel filter change is also cheap insurance... if you don't know when it was done, change it and now you do.<br /><br />You really ought to get the manual for that motor.. you can buy it right here on I boats and it should be the very first thing you do, before you start tinkering with it... study it and become familiar with your motor and you will have a lot more fun and a lot less hassle when you do proper maintenance. The book will also contain the specs to answer your other questions.<br />There are no online service manuals that I am aware of.<br /><br /><br />Best of luck<br /><br />Craig<br /><br />,