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78 115 hp sputter sputter chug chug??

C

Canadianwalleye

Regular Contributor
Well I’ve come a long way from where I was. Originally I got the boat a few weeks ago and it ran decent. Would chug in low idle or low speeds but I would just give it more throttle and it would stop. A few days later and the engine wouldn’t start at all. I inspected what I could see and there was fuel coming from 1. The fuel pump connection too the main fuel line= ordered new fuel pump, installed
2. Lots of fuel from the air silencer cover. Usually means your carbs are flooding.= took out the carbs and did a cleaning. Found large peice of rubber under the seat for the float needle so I removed it and cleaned out the hole. Replaced the float pins and housing on ONE of the carbs as I only had a one kit with them included. (The other didn’t have them). Next I removed the slow and moderate speed orifice screws and found another peice of rubber in the intermediate jet. Removed the jets to inspect further and they were fine. Sprayed out the insides of the sprayer home ( did not remove the aluminum covers to thoroughly clean inside as I’ve never done a carb cleaning before). Put the jets back in and put the carb back together with basically all new gaskets (that I know of).
Put everything back onto the engine and try to start it and it starts!! The problem I’m having now is the chug and bog and low idle/speed... I made a video of it to get a better perspective as too what I’m talking about... I’ve tried the only idle screw that is in the engine and if I go lower rpm then what is shown in the video, she chugs and sputters very bad and dies!!

what do I do too fix this?
Heres what it looks and sounds like;
 
CEC9D60D-E1D0-4D24-AF98-917ADA85A926.jpgHere’s what the setting is for the throttle... can’t go lower as it will stall the engine but the motor goes into gear... kinda high rpm to do it but it goes (just)
 
My 2c is that that motor is not running on all cylinders and the popping etc indicates that you may also have electrical issues on top of carb issues. I have had bad power packs cause similar things.
Have you checked electrical system with a spark jump test? Can you wire a timing light to check for spark when it does that pop and chug?

You should also check all connections, coils and the power packs. A bad diode can cause an idle like that as it causes erratic and intermittent firing
‘the CDi site has a real good trouble shooting guide.

you have quite a few posts so I hope I haven’t missed where you might have done this stuff already.

my final 1c, is that the Lync and sync needs to be precise, these motors will bog every time on the water if it’s not perfect. As an example if throttle advances too early vs the spark advance it will die.
 
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I readjusted the carb float “again”. Runs better and better each time I do but still can’t seem to idle at a decently low rpm (guessing, no gauge to say)
i just got this boat last weekend and the cylinders have what I believe to be compression tests from previous owner. One cylinder reads 30 while all he others read 125-130...
 
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