Bogging issue on 3.0 mercruiser solved?

[LilRedNeckGirl]

well to an earlier post, we had twins each bogging on a hole shot start. it was suggested that accelerator pumps, or power valve issues might be the blame.
The mechanic again rebuilt the carbs, still no satisfaction, still bogged.
He called mercruiser, and spoke directly to the carb specialists.
The mechanics there say the following.
"Todays gas is nothing like the gas used back in the day, (1985) . the extra gas pumped in on a hole shot isnt enough in many cases, to get the boost needed with the extra load on the engines, so they bog & stall. The jets are too small to allow that gas to work effectively, and take too long to inject it into the carb intake."
The remedy, bore out the two ports where the accelerator pump shoots the gas into the carb venturi. They recommended a 1/16th opening. On dyno tests, it preforms perfect. water test is next weekend , weather permitting.
Again , this issue was on a 1985 wellcraft 24.8 sportsman, with twin mercruiser 3.0 140 hp I/O drives. Carbs are stock.

 

[ziggy]

Re: Bogging issue on 3.0 mercruiser solved?

thanks for the follow up. it's always good to hear what solved the problem. interesting notes on the expensive apparently less than flammable fuel we get these days.

1985 wellcraft 24.8 sportsman, with twin mercruiser 3.0 140 hp I/O drives. Carbs are stock.

that sounds like a nice set up....

 

[Bondo]

Re: Bogging issue on 3.0 mercruiser solved?

interesting notes on the expensive apparently less than flammable fuel we get these days.

Ayuh,... I hear ethanol has about 15% less energy than gasoline,...
So,... I guess it makes sense...

Good Luck with the sea trials...

 

[LilRedNeckGirl]

Re: Bogging issue on 3.0 mercruiser solved?

We like it. Took a big chance and bought it after 5 years setting dry. ended up only doing a head job on one engine and cleaning replacing fuel system components. as expected, its been a full year of chaseing gremlins, but seemingly, we are at the end of that road.
We love the 3.0 twin setup. we are traveling over 40 miles, two times each weekend in a tidal river, and putting about 30 gallons of fuel in at the end of the weekend. my 70 johnson burnt that much or more easily on a 15 footer. This year, we added new graphics, a power anchor winch, and a dual beam fish/depth finder. that should make the days a bit more enjoyable.
The cabin interior has been modified, with stove and sink removed, and a big counter top installed. as we camp at our marina, the cooking aspect was pointless on the boat. Ill get some pictures up at some point, but for now it can be seen at www.whiskerfish.webs.com

 

[LilRedNeckGirl]

Re: Bogging issue on 3.0 mercruiser solved?

Ethanol. The boaters worst nightmare. forget the 15% loss of power, the damage to rubber and iron parts, the biggies are,
1] it vaporizes at a much higher temp, making cold starts and hole shots more difficult.
2} and the real issue, alcohol mixes with / absorbs and allows water to become dissolved in the gas. Marine environments are damp and humid, and all fuel tanks are vented, so with normal heating & cooling, the tank breathes and humid air moves into the tank, moisture condenses and enters the fuel, redissolves and is not removed by a separator filter as the water is dissolved in the gas/alcohol blend. Remembering back, the old fashion, Gas Dry additives, were nothing but ethanol. @ Water mixes with alcohol, alcohol mixes with gasoline , therefore water is mixed with gasoline. AND, Water doesn't burn !!!!
remember, ethanol fuels come out of the fueling dock with at least 2% water to start with. That is, from what my research shows, is the industry standard.

 

[achris]

Re: Bogging issue on 3.0 mercruiser solved?

... ethanol fuels come out of the fueling dock with at least 2% water to start with. That is, from what my research shows, is the industry standard.

So, we're back to running steam engines... Don't you just love progress....

 

[petrowski53]

Re: Bogging issue on 3.0 mercruiser solved?

That sounds like a good idea. I have an '87 120 (2.5L) and I wonder if I could do the same thing to squeeze out a little more power for hole shots. My engine runs great, but it just doesn't seem to have the oomph it should. When I was a kid in the early 90's, my family had an 1985 Sea Ray Seville Cuddy with the 120 (with more hours on it then my boat has now!) so I know it should perform better. What exactly did you do? You only increased the bore on the accelerator pump jet? Let us know how it performs! If all is well, I think I might have a new weekend project

 

[achris]

Re: Bogging issue on 3.0 mercruiser solved?

... and I wonder if I could do the same thing to squeeze out a little more power for hole shots. ...

If you're looking for hole-shot, try drilling a small hole at the root of each propeller blade, or better still get a Laser II prop with the vent plugs removed. Even that little 120 will pull skiers arms off with one of those props....

 

[petrowski53]

Re: Bogging issue on 3.0 mercruiser solved?

If you're looking for hole-shot, try drilling a small hole at the root of each propeller blade, or better still get a Laser II prop with the vent plugs removed. Even that little 120 will pull skiers arms off with one of those props....

What would drilling holes in the tip of each blade do?

The Laser II props look nice, but being one of the most expensive props out there they should be. Unfortunately, It would be hard for me to justify $300+ for a prop on my boat. This season's priorities lie in cosmetic repairs to the interior. Once those are out of the way, maybe next season I can look into getting a nice prop. I do however have a couple of extra old props that I could "experiment" with ( i.e. I wouldn't mind drilling holes in them).

I would love to be able to put a bigger carb on the engine, but every time I have seen the question posed, everyone says it can't be done on the 120.

 

[Bondo]

Re: Bogging issue on 3.0 mercruiser solved?

What would drilling holes in the tip of each blade do?

Naw, the Other end of the blade,...
At the Root of the blade,...
The hole is drilled through the Barrel of the prop to ventilate it abit at launch...

 

[achris]

Re: Bogging issue on 3.0 mercruiser solved?

 

[achris]

Re: Bogging issue on 3.0 mercruiser solved?

.... Unfortunately, It would be hard for me to justify $300+ for a prop on my boat.....

In Australia we pay $300 for a bog stock Ali prop. The S/S job are up near $1000.

 

[LilRedNeckGirl]

Re: Bogging issue on 3.0 mercruiser solved?

Ok, Drilling out the accelerator pump ports helped 100%. On the weekend, not 1 issue of stalling on fast starts. . The ports were drilled out to 1/16th . my mechanic did the modification, recommended by mercruiser tech support, so not sure what is involved. You might google " Ace Marine" in Stuarts draft virginia and speak to the mechanic or go directly to mercruiser carb tech support for questions...
It still doesnt have that really strong shot, but again, they are 140 hp 4 cyl engines.... but it sure beats the issues we had before. Now at least, we can get a water sports thing going on without drowning the guy on the end of the string.... we are up on plane in a few seconds, and everything is running great. We lost nothing in fuel efficiency, as we did about 110 miles of running, and used less then 50 gallons of stabilized winter fuel.... im hopin after thats run out, with fresh fuel , we do a bit better on power and efficiency..
Im going to try that vent hole in the prop thing. We used to do that years ago on the outboards, had totaly forgot about it for these engines. Looking at new props soon anyways as normal maintanace so playin with the old blades wont risk much....
On the weekend, the STE outdrive is sweet. runs quiet, no issues. great replacment drive at a sweet price...
well, past that, the new depth finder is installed, just wish they worked at cruisin speed.... also high water alarm is in, so next improvement is installing a live well. im just a bit scared when it comes to drilling any hole below the water line.... any suggestions on alternative methods to get water into a live well?

 

[LilRedNeckGirl]

Re: Bogging issue on 3.0 mercruiser solved?

Just a few pics.. http://whiskerfish.webs.com/apps/photos/photo?photoid=106783066 , http://whiskerfish.webs.com/apps/photos/photo?photoid=121889433 , the boat and why it is aptly named, "WHISKERFISH"

 

[crenche]

Re: Bogging issue on 3.0 mercruiser solved?

well to an earlier post, we had twins each bogging on a hole shot start. it was suggested that accelerator pumps, or power valve issues might be the blame.
The mechanic again rebuilt the carbs, still no satisfaction, still bogged.
He called mercruiser, and spoke directly to the carb specialists.
The mechanics there say the following.
"Todays gas is nothing like the gas used back in the day, (1985) . the extra gas pumped in on a hole shot isnt enough in many cases, to get the boost needed with the extra load on the engines, so they bog & stall. The jets are too small to allow that gas to work effectively, and take too long to inject it into the carb intake."
The remedy, bore out the two ports where the accelerator pump shoots the gas into the carb venturi. They recommended a 1/16th opening. On dyno tests, it preforms perfect. water test is next weekend , weather permitting.
Again , this issue was on a 1985 wellcraft 24.8 sportsman, with twin mercruiser 3.0 140 hp I/O drives. Carbs are stock.

Ok, I know that I have not contributed to this forum site before but I have been lurking for about a year now. I have a 1990 17ft Maxum 3.0 4 cylinder with mercarb, that has needed some tlc since I bought it. It was stinking cheap ($660)! All I really needed to do was put a out drive in it because the previous owner had a huge crack in the lower unit which burned up the upper unit. Found another outdrive for $300. So after a gimbal bearing replacement I have an awesome boat for less than $1200. To make a long story even longer... I had the bogging problem with pulling tubers and trying to pull skiers. I tried to go to WOT from idle and it would bog/hesitate and then kick back in. Thinking it was the accelerator pump as well I rebuilt the carb. Today, I started the boat from it's wintery sleep and reved it a couple of times and it seemed to have the same bogging problem. I was disappointed. So I decided to try the drilling of the accelerator pump jets. I used the 1/16th drill bit and opened up the holes. I reinstalled the carb and tested it. It seems to fix the problem. I slam it down from idle and it just revs right up, no hesitation!! I'm extremely excited. Granted, this is all on the trailer, I haven't taken it to the lake yet but I am confident that this has fixed this problem.

I have been reading a lot of the advice that has been given to people that having similar problems and it has been suggested to either get a new prop or the carburator cannot be rebuilt properly. I think this method is the FIX for this problem. I think that the fuel jets are too small for the ethanol gas and just need to be bored out a bit. It was really easy to do as well. I can't say that it wil work for other carburators and maybe on newer models mercruiser has fixed the problem but I strongly believe in this fix. I can tell how I drilled the jets in more detail if someone else needs that information.

I'm no expert on all this but I hope my 2 cents helps others as well. Oh and thanks for all the helpful information that I have gleaned from this site. IT HAS HELPED ME SO MUCH!