100HP Merc Outboard ? Slow Acceleration & Stalling

[l_striker]

I recently purchased a 1988 16? Sea Ray Seville with a 100HP Merc/Sea Ray engine on it. Took it out for the first time yesterday and it ran very well for the most part. There are, however, two problems:

1) Slow Acceleration ? I?m not expecting to take off like a rocket but I do know it shouldn?t take as long as it does to get up to top speed (around 40 MPH or so).

2) Stalling in Neutral ? It stalled out on me a few times while in neutral. If I applied the choke it would idle fine without stalling

Prior to taking it out, I replaced the plugs and impeller. I also put 10 gallons of fresh gas in the tank in addition to the 10 that was already in there (probably a year or so old). I also added Stabile (fuel stabilizer).
I?m thinking that the lower carbs are probably dirty and all I need to do is clean them? Before I go ripping them apart should I try using the ?Deep Creep? spray or ?Sea Foam?? I plan on doing a compression test but not until I pull the boat out of the water in a few weeks.

 

[verado7]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

does the primer bulb stay firm or go soft after squezzing and holding it .
have someone check the bulb for firmness on the hole shot and full throttle running - if soft try pumping it -does the motor pick up ?

 

[Traceyh]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

I suspect if you are having to apply choke during idle, you will have to do a carb clean, as a low speed circuit clogged or partially clogged would cause the exact symptoms you are describing. How long has the boat sat? Im guessing from your post, at least a year. That alone make me think carb cleaning will be in order.


Seafoam is a waste of time and money, its simply a mixture of pale oil, cigarette lighter fluid, and rubbing alcohol. It wont magically clean your carb.

 

[Dave1027]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

1) Slow Acceleration ? I?m not expecting to take off like a rocket but I do know it shouldn?t take as long as it does to get up to top speed (around 40 MPH or so).

2) Stalling in Neutral ? It stalled out on me a few times while in neutral. If I applied the choke it would idle fine without stalling

You are thinking the lower carbs being dirty are causing the stalling? Nope. The lowers have nothing to do with idling. That function is all on the upper two.

What rpm does it idle at?

How slow is the acceleration? How long does it take to get to 40 mph? Mine takes about 10 seconds I'd guess. Never timed it. What size prop do you have? I have a 17 pitch SS.

 

[sschefer]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Change the inline fuel filter and add an appropriate amount of QuickSilver QuickClean to your fuel and see if it improves. The statement about upper carbs being the idle carbs is correct, this is a 2+2 motor.

Hesitation during acceleration is something you can tackle after you get it idling right.

One thing at at time.

 

[l_striker]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Thanks for the advice! I'm almost positive the boat has been sitting (on land) for at least a year. It takes a good 45 seconds to get up to 40 MPH. I noticed that it does idle fast...close to 1500 when warm. I'm going to start with the fuel filter since I have an extra and the Quickclean. If that doesn't work I'll tackle the carbs. I'm really suprised to hear that about the Sea Foam. The other posts I've read about it make it sound like a miracle cure for carbs.

 

[Dave1027]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Listen, it's not the fuel filter. We can help you to get this thing running but you need to be open minded to our suggestions. Sea foam may have it's uses but no way is it some miracle.

First thing, what size prop is on it?

2nd, so it idles high and sometimes dies. Does it cough and die? That may be a lean pop on the bottom two carbs. I have seen that before. Too much gas builds up in the bottom two and they actually fire when they are not supposed to. As the excess fuel burns off it goes lean and coughs.

Before you go any further you need to perform a sync and link. Also while your at it do a compression test just to see what you have.

 

[l_striker]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Don't get me wrong, I appreciate the help. I've worked on a lot of engines and this site has been a life saver. Two posts below yours, however, "sschefer" said to change the fuel filter so I said I would. Can you tell me how that's not being open minded?

I had also never heard of Sea Foam before reading these forums so I figured it's worth a try. That's being pretty open minded in my book. Most posts say it works wonders. I've never tried it so I'm throwing it out there to see if it's a possible solution. Regardless, the worst that can happen is that I'm out $10 if I use it. The best thing than can happen is that I save myself a whole lot of time and money if it actually works.

 

[Mi duckdown]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

I also put 10 gallons of fresh gas in the tank in addition to the 10 that was already in there (probably a year or so old).
That is a problem you need to consider.
Start fresh.
Can you hook up a GOOD/ Clean portable tank?

 

[Traceyh]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

I had also never heard of Sea Foam before reading these forums so I figured it's worth a try. That's being pretty open minded in my book. Most posts say it works wonders. I've never tried it so I'm throwing it out there to see if it's a possible solution. Regardless, the worst that can happen is that I'm out $10 if I use it. The best thing than can happen is that I save myself a whole lot of time and money if it actually works.

It only cleans an already clean carb, it does nothing for a dirty or gummed up carb. Yes, I stated all that correctly. While you are researching Seafoam, also research "snake oil", you will find they have a lot in common. The $10 that you waste on Seafoam can be spent on a couple of cans of spray carb clean for when you disassemble the carbs to clean them properly.

 

[l_striker]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

That is a problem you need to consider.
Start fresh.
Can you hook up a GOOD/ Clean portable tank?

You're right, I always try to start fresh when old gas is involved. The problem is that there's a 20 gallon, built-in, gas tank. I would have loved to have pumped out the old gas but I don't have the equipment or a place to dispose of it. Are you suggesting that I should try the portable tank to troubleshoot or as a replacement?

 

[Mi duckdown]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Yes.

 

[l_striker]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

It only cleans an already clean carb, it does nothing for a dirty or gummed up carb. Yes, I stated all that correctly. While you are researching Seafoam, also research "snake oil", you will find they have a lot in common. The $10 that you waste on Seafoam can be spent on a couple of cans of spray carb clean for when you disassemble the carbs to clean them properly.

I totally agree that NO spray, liquid, etc is going to take the place of taking apart the carb and cleaning it right. A lot of people seem to like it though (see thread below) so I'll give it a shot since I already bought it.

http://forums.iboats.com/showthread.php?t=170490

 

[l_striker]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Yes.

Yes, replacement or Yes, troubleshooting?

 

[Mi duckdown]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Fresh gas and oil. WHAT DON'T you get

 

[l_striker]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Fresh gas and oil. WHAT DON'T you get

I don't get why you have to be such an @SSHOLE! I asked a simple question and get an attitude. What's your problem???

 

[milehighboater]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Wow this is getting a bit heated for an idle issue.
So... I think what mi duckdown was saying was do the test with the portable tank to rule out any bad gas issues. I don't feel you need to replace the tank. With that being said I doubt one year old gas is too bad but it would be good to go back out to the lake and burn a bit more off before filling it up again to do the tuning. As for the Sea foam it doesn't hurt anything to try it out. Where it will not magicly take apart your carb and polish every crevis it does a good job busting up some carbon deposits and cleans up some of the sludge (not varnish).
So back to the post... how does it act when it dies in idle ie just putting along and nothing or cough then dies?

 

[starcraft1982]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

Some on here think that if they give advice,they have to give "remarks"also.Just how it works.Anyhoo,you can drain old gas by simply getting a can(bigger than 20 gallon)in your case,unhook connection from motor,cut(or take)it off,and use the bulb to start the flow,or prime,if you will.it will come out(albeit slowly).I would also suggest cleaning the carbs thoroughly as dirty carbs cause a lean condition to cylinders.Not enough gas=noy enough oil and in anyones book,thats BAD for a motor!Also,you could very well have a bad fuel pump.The choking making it better points to carbs or fuel pump.Get a rebuild kit for fuel pump and put it in.Cheap and easy(we all like that!).And the reason i said cut off fitting on fuel lines is you want to replace them anyway,bulb included.Ethanol will rot them out inside.Ad for carbs,theyre not that hard either and will serve your motor well even if not the cause.Good luck.

 

[Mi duckdown]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

I'm Not a## hole. Trying to help you.
To eliminate fuel problem.
A little thin skinned.
Read all your posts. Done.

 

[verado7]

Re: 100HP Merc Outboard ? Slow Acceleration & Stalling

man overboard