Hesitation - 3.0 Mercrusier I/O - 135hp

[RAN209]

I just inherited a 1996 Sea Ray 175 with a 3.0 Mercruiser I/O. The boat is in great shape with low hours, but has been garaged for 2 years. It had a half a tank of gas in it when I got it. So I topped it off and headed to the lake. Idled rough and ran rough. A bottle of fuel system cleaner and two tanks later, it runs better, but it still hesitates when accelerating hard. I just changed the spark plugs and cleaned the distributor cap. What should I do next? Should I try another bottle of carb cleaner?

 

[Haut Medoc]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

Welcome to iboats <br />Another can of carb cleaner won't kill it....<br />Change your water separating fuel filter.....<br />Run a tank or two of new gas & see if it improves even more.....<br />Is hard acceleration a smooth, easy engaging of the throttle or is it "put it to the hammer" in one motion?<br />You may never get the instant response from going no throttle to full blast....<br />My advice is: run some more new gas through it & clean your flame arrestor .....JK<br />Changing your points may help, too....<br />Esp. if it has been sitting for 2 years...

 

[Mile-High Mariner]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

Come on, Medoc - you know a '96 3.0 isn't going to have points! Mercruiser dumped all else, including the DDIS, in favor of the Delco EST ignition years back, several years before Ran's motor was produced.<br /><br />Ran - you indicated that your SeaRay was garaged for two years prior to your taking possession, but do you know when it was last run? Your profile doesn't tell us where you live, but if your environment is humid (or even if it's not, in particular) you have to put a good fuel dryer as well as a good fuel stabilizer if you're going to store it for such a long period. Water will condense inside the tank (there are numerous threads on this forum that argue over whether you should store the boat with the tank empty or full) and collect in the bottom. The only way to get it all out is to pump it out, and the only time I had to do it, I pumped a couple of liters of gas into the tank and suctioned it out, repeating several times until I was satisfied that I had removed ALL liquid, fuel, water or other, from the tank. Medoc's suggestion to change your water-separating fuel filter is sound advice, too. Good luck!

 

[dough41]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

I bought a 98 with a 3.0 mercruiser with similar problems... changed out both the fuel filters (inline and in the carb housing)and the fuel/water seperator twice each and rebuilt the carb ( accelerator pump)and it runs beautiful.hope this helps.

 

[RAN209]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

Thanks. Yeah, when i say hard acceleration, I'm talking from a dead still. Once it reaches plane, it runs fine. Don't think my boat is equipped with the water/fuel seperator. But i did think that replacing the fuel filter would help, but couldn't find anything about it in any of my books.

 

[KRS]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

Over the two years of storage, any gasoline left in the carb would have evaporated, leaving behind a varnish residue.<br /><br />It may be time to buy a carb rebuild kit and instal it. Not an impossible job, easy one-day type of thing.

 

[Haut Medoc]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

My apologies, I thought I read '76....<br />You do not have points as Mile High Mariner so graciously points out ....<br />If it runs, keep on running it, & use the carb cleaner & see if it improves, if that fails to improve performance , a carb. rebuild is in order.....JK

 

[tommays]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=016698#000002 <br /><br />If you search on member RON7000 he has written a lot about how to adjust the carb to fix this problem<br /><br /><br />tommays

 

[dough41]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

Ron;<br />I failed to say that I added a fuel/water seperator and it did take out alot of crap that been settled in the tank. I changed that twice and the hesitation you mentioned was the same as mine, in that after I pushed it down (the throttle) and it got over the slight hesitation and on plane it also ran well. Changing the accelerator pump and cleaning out the carb, after that it ran great. Hope this helps.

 

[RAN209]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

I guess i'm gonna bust open the carb and see if I can't get it cleaned out. I think I may try another fuel additive first. Any suggestions?

 

[harveje]

Re: Hesitation - 3.0 Mercrusier I/O - 135hp

my 90 3.0 did same thing, took carb apart, sprayed the crap out of it blew it out with air hose, same thing, ran pretty good but fell face first on hard accel. Then it started flooding. But a kit in over the weekend and both / all problems started going away. These boats will not jump out of the water on hard accel, but should have a good ramp up to WOT, also depends on prop how fast the ramp up is.If yours does not have a water seperator put one in line. Not sure on yours but I think my 90 has a filter in the fuel pump that I need to change.