3.0L Mercruiser hard start, will not idle, hesitation

This is my first post so I will try not to write a novel. <br />The leading particulars are;<br />I/O 3.0L Mercrusier Model Number OC464636.<br />The problem I am having is hard starting, rough idle and hesitation during acceleration. WOT is at 4200 within specs and it runs great.<br />I have overhauled the Mercarb 2 bbl with a Sierra overhaul kit from West Marine using information from Clymer and Sierra. It had the solid needle set up so I replaced it with the same.<br />The Ignition system has been upgraded with a new Pertronix Ignitor 2 system with a new Accel SuperCoil. There are new plugs, wires, rotor and dist cap installed. I have checked this system and it seems to be working fine.<br />I have adjusted the idle speed and set the timing to the specs as per the Clymer manual.<br />I thought I may have set the float level wrong so I tore the carb down and checked. It was fine. The engine started easy and ran great on the trailer. Once I put it in the water same problem.<br />I suspect the carb since I have pulled the new plugs and am seeing indications of to much fuel.<br />I know I am missing something but I am out of ideas and could use any opinion! I am beginning to think this boat hates water.<br />Thanks in advance

Re: 3.0L Mercruiser hard start, will not idle, hesitation

3 things putting in the water changes,1.at rest angle of boat and that effects carb float level ,2 .back pressure on exhaust, 3.load on engine in gear.

Re: 3.0L Mercruiser hard start, will not idle, hesitation

Thanks for the reply, and the food for thought. I had thought of the carb float level, but decided not to move it since the manual required a certain seting. This boat does set in the water at a different angle than on the trailer. Would you agree that I would need to lower the float level?<br />The prop is the same that has been on the boat for two seasons without trouble, so I am thinking that scenario is eliminated. Shouldn't the same be said of exhaust back pressure? <br />Again thank you! I need someone to help get the old thinking hat straightend up again.

Re: 3.0L Mercruiser hard start, will not idle, hesitation

http://www.marinemechanic.com/site/page152.html i was really pinning my hopes on boat attitude and float setting. hope this provdes some help.

Re: 3.0L Mercruiser hard start, will not idle, hesitation

akriverrat.....I will dance at your next wedding! The link you sent may have cleared up my problem. Both Clymer and the overhaul sheet from Sierra list float drop as 1 3/32". The information you sent shows 13/32", which makes more sense now that I think about it. <br />I am taking off work to go and change it now. Hopefully this was the problem all along.<br />Thanks again. I'll let you know how it goes.

Re: 3.0L Mercruiser hard start, will not idle, hesitation

I have the same problem with my mercuriser 2.5 I/O

Always runs good in the yard. I put it in the water yesterday and it started but did not get up to a smooth idel.

Nothing had changed so I was really lost as to what the problem could be?

Then I remember one thing that had changed.......... Everytime I ran it in the yard with the rabbit ears the cover was off the engine. When I put it in the water the cover was on the engine and I forgot to turn on the blowers so the Carb. could get lots of air.

Have not tested this yet but I hope it works.

Any thoughts, thanks
Duke of ....

Re: 3.0L Mercruiser hard start, will not idle, hesitation

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