1978 Mercury 700 - 3 Cyl. 70HP - great idle but no acceleration

I have recently tuned this engine that I have purchased one month ago. New starter, new plugs, refurbished carbs, everything looked good but. <br /><br />I have put it in the water for the first time yesterday and it started immediately. The idle was perfect. <br /><br />It went into gear (both reverse and forward) without any problems but, once I have cleared the pier I started to accelerate but the engine did not responde, it sounded like it was sort-of flooding or choked. I am very, very new to boating, could someone give me a hint on what it could be and how to fix it? Thanks, Christian

Re: 1978 Mercury 700 - 3 Cyl. 70HP - great idle but no acceleration

Re-check the idle mix screws..... or it might be over-propped and *can't* spool up. I assume you did the timing and synch.<br /><br />-W

Re: 1978 Mercury 700 - 3 Cyl. 70HP - great idle but no acceleration

Hi Clams Canino, thanks for your quick reply. No, I actually did not do either one of those - timing and synch - I was thinking about looking for a manual on these engine at the local West Marine store.<br /><br />I have just removed the cover and I have access to the carbs screws. I was trying to figure out if it had anything to do with the link to the mercontrol but I don't think so (I am not positive) - now I need to understand which one is the "idle mix screw". Do you have any other suggestions?<br /><br />Thank you again. Christian

Re: 1978 Mercury 700 - 3 Cyl. 70HP - great idle but no acceleration

I wouldn't use just the manual from West Marine (likely Seloc or Clymer if even available). I highly rec. getting the original mercury service manual. You can find them on ebay or Http://www.mercurypartsexpress.com

Re: 1978 Mercury 700 - 3 Cyl. 70HP - great idle but no acceleration

Do what Clams said, also check that the fuel lines are tight and not allowing air to get sucked into the system.<br />another culprit could be that the fuel pump diaphram needs changing.

Re: 1978 Mercury 700 - 3 Cyl. 70HP - great idle but no acceleration

Hi guys, ok I have discovered that I had a poor ground connection to the battery. I fixed it and then, after attaching the ears to the engine I started it to see if it made any difference.<br /><br />No problem starting and idling, I engage the forward gear and started to accelerate. It was just beautiful. The engine roared! Same thing in reverse.<br /><br />Yesterday I took my two kids on the boat expecting a powerful ride... instead, same problem happened!<br /><br />It seems as when the engine gets into the water it just looses power... once again I was able to go, at almost full throttle at about 7 MPH. I tried to slowly add for acceleration gradually to see if maybe the engine would rev up but instead it died. It took me several minutes to get it started again. <br /><br />To conclude, on the ground with ears - perfect!<br />On the water ...<br /><br />Please help! Thanks, Christian

Re: 1978 Mercury 700 - 3 Cyl. 70HP - great idle but no acceleration

If the throttles are opening properly, it sounds like the high speed jets in the carbs are dirty and the carbs should be cleaned, the engine will free rev with no load on it as it does not require as much fuel

Re: 1978 Mercury 700 - 3 Cyl. 70HP - great idle but no acceleration

Luna, not a good idea to rev the motor with muffs on. I understand the motor could run away and fly apart.<br /><br />Jerry