72 merc 80 hp hard starting

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turboapache

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I bought this Basstream 550 pro bass boat with a merc eng and have had to use carb cleaner spray to start it. The bulb does not seem to want to pump up hard. I put a new diaphram in the fuel pump with no help. I can hear the fuel swishing back and forth in the lines of the eng but cant seem to get the bulb to pump up hard. I have replaced the fuel lines and bulb. I cant find any fuel leaking anywhere on the eng. Anyone have any ideas?
 
jimmbo

jimmbo

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Re: 72 merc 80 hp hard starting

any chance you installed the primer bulb backwards?
 
jimmbo

jimmbo

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Re: 72 merc 80 hp hard starting

Have you checked for an air leak on the fuel system prior to the primer bulb?
 
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Chris1956

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Re: 72 merc 80 hp hard starting

You are holding the choke button down, cold start lever all the way up and cranking her until she starts, right?
 
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Chris1956

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Re: 72 merc 80 hp hard starting

You need to have some way to advance the throttle in neutral, or it will be real hard to cold start. Does your control have a throttle only button? Maybe the throttle handle pulls straight out from the control for Throttle-only?
 
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turboapache

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Re: 72 merc 80 hp hard starting

Yes, it has the throttle only button. I have replaced the quick disconnect that plugs into the motor. Now with a shot of carb cleaner it starts and runs and a little throttle helps it to start. But without a shot to begin with it will not start even with the choke held closed. After having run for a while it will start fine with just a bump of the key, but after an hour it is back to square one.
 
jimmbo

jimmbo

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Re: 72 merc 80 hp hard starting

Have you checked the float levels? low fuel levels can create difficult to start issues
 
chum1

chum1

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Re: 72 merc 80 hp hard starting

That swishing sound more then likely is fuel passing through the needle and seats in the carb (s), at the next opportune time I would change those parts with the merc. brand needle/seat kit (not seirra unless u want to do it over again) that will probably solve your fuel problem.
 
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Chris1956

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Re: 72 merc 80 hp hard starting

I would check the compression. Motors with low compression act like what you are experiencing.
 
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CharlieB

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Re: 72 merc 80 hp hard starting

There are a few things that can cause a primer bulb to feel like it is not pumping up.

First is the bulb itself, it could be old, the valves in it may be leaking.

Air can be sucking into the system anywhere before the bulb.

The fuel pump and/or carbs can be flooding, leaking fuel.



Your second problem, not starting unless given a 'shot' of spray.

Verify the choke/enrichener is working.

Check cranking speed, a dragging starter, or poor battery cable connection can reduce cranking speed and contribute to hard starting.
 
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turboapache

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Re: 72 merc 80 hp hard starting

I solved the bulb problem by installing a new quick disconnect on the end of the hose where it goes into the motor. New hose and bulb. Good compression. New fuel pump kit. I had the boat out yesterday and once started it ran out well, lots of power. My only problem now is the fact that it will not start without the spray even with the choke full on. Do we have any certified Mercury mechs out there who have been thru this?Thanks
 
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Chris1956

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Re: 72 merc 80 hp hard starting

You are advancing the throttle with the "throttle only" button?
 
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CharlieB

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Re: 72 merc 80 hp hard starting

1972, the carbs still had an actual choke shutters. With the motor cover off you should be able to SEE if the choke shutters are closing when you hit the choke button, are they?
 
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