1986 Starcraft 22ft islander, 2.5 or 3.0 mercruiser? Having some small issues any input helps!

Hello all,

I am on here to get a little more information pertaining to my dads boat. I am mechanically inclined, I work for chrysler as a field support rep so I know my mechanics. The trouble I am having is that I am unfamiliar with marine engines and where to obtain the information. It shows a 140 on the valve cover, I cannot find any serial numbers to indicate if the boat is a 2.5 or 3.0. The motor has been replaced so I am hoping we have the correct motor and the valve cover is not swapped. The title shows a 140hp motor which to me indicates*the motor is the 3.0L. *Any help is greatly appreciated!

To start the boat is running it just seems to have a rough idle sometimes stalling out. It can be very stubborn and the low rough idle will allow the boat to stall when going into gear. Once the boat takes off it will run fine, occasionally it will start to mis and run like crap. The carb has been rebuilt with a new carb kit. We replaced the fuel filter attempted to install a electric fuel pump which*ended up being a waste of time due to the pump over heating! The original mechanical fuel pump is on the boat again and it starts and runs but as stated before I need to figure out if I need to tune the carb or simply replace it. My dad wants to go holley I think it may be a bad idea seems Rochester carbs are not bad. I have verified that we*are getting fuel to the carb, we have replaced cap, rotor, plugs, wires.*The other piece to the puzzle is the PCV hose that links the*valve cover to the carb.*At this time is simply a rubber hose that is hose clamped to the*cover and then attached to the carb. There is no PCV valve or internal piece on this. Is there suppose to be a PCV type valve or something to eliminate the oil from blowing into the carb at wide open throttle? I am not sure if the way this is set up is affecting the operation or not. I appreciate any input. Thanks

Ktmhiflyer said:

Hello all,

I am on here to get a little more information pertaining to my dads boat. I am mechanically inclined, I work for chrysler as a field support rep so I know my mechanics. The trouble I am having is that I am unfamiliar with marine engines and where to obtain the information. It shows a 140 on the valve cover, I cannot find any serial numbers to indicate if the boat is a 2.5 or 3.0. The 3.0l has a pulley, 'n harmonic balancer, the 2.5l has just a pulley...The motor has been replaced so I am hoping we have the correct motor and the valve cover is not swapped. The title shows a 140hp motor which to me indicates*the motor is the 3.0L. *Any help is greatly appreciated!

To start the boat is running it just seems to have a rough idle sometimes stalling out. It can be very stubborn and the low rough idle will allow the boat to stall when going into gear. Once the boat takes off it will run fine, occasionally it will start to mis and run like crap. The carb has been rebuilt with a new carb kit. We replaced the fuel filter attempted to install a electric fuel pump which*ended up being a waste of time due to the pump over heating! The original mechanical fuel pump is on the boat again and it starts and runs but as stated before I need to figure out if I need to tune the carb or simply replace it. My dad wants to go holley I think it may be a bad idea seems Rochester carbs are not bad. It's best to replace, What's There,...I have verified that we*are getting fuel to the carb, we have replaced cap, rotor, plugs, wires.*The other piece to the puzzle is the PCV hose that links the*valve cover to the carb.*At this time is simply a rubber hose that is hose clamped to the*cover and then attached to the carb. There is no PCV valve or internal piece on this.That's as it should be, No pvc, just a Vent, free flowin',... Is there suppose to be a PCV type valve or something to eliminate the oil from blowing into the carb at wide open throttle? I am not sure if the way this is set up is affecting the operation or not. I appreciate any input. Thanks

Click to expand...

Ayuh,... Welcome Aboard,.... Have ya done a compression test,..??

It shouldn't be blowin' oil out of the vent, or very much anyways...

Rochester is a damn good carb when set up right. Do both idle mixture screws adjust when you tune the carb? I remember a man who found a problem in the wire harness on the digital ignition...cracked wire in the harness. I agree w/Bondo...a compression test is a must do.

I have done a compression test I came up with 115 across all 4. There was a minimal increase with a wet test but only a couple PSI. I am only aware of one air mixture screw and one idle adjustment. Either way the motor will change with both.

I believe I have a carb issue but I want any ideas available! I came across the base gasket thickness on a post in here. I am going to check that out and see what we can come up with. Do we have any general specs for the air/fuel mix screw? 1.5-2 turns? Thanks Guys!

Was the throttle wide open...115 PSI isn't the best but they are wearing evenly. If there is only one idle air mixture screw in the middle of the base then it's a Mercarb and requires base gasket Merc. PN 27-807982. I have one left you can have if needed...send me a PM w/your mailing address. I start the I/M screw at 1.25 turns CCW from fully CW.

Pull the valve cover off, stamped on the head is the info you need. Say you have a 2bcg carb, 2 adjustment screws lead me to believe this, pull off the carb and rebuild it. Rebuild kits abound. Below is a link.. rebuild carb. and how to go thru your fuel system.

Hook your gauge up and see what psi the fuel pump is giving you. 4-7 no less not more. Get back to us with what you found and the outcome.

clean carb pump tank

Hello All,

I want to thank you all for you input. I sat back and thought a little about this, the boat was running decent when it would first start and then once it ran a little longer the boat would start acting up. I thought maybe it had to do with the choke but was to inconsistent to be a choke issue. If it was the choke it would run like crap all the time not randomly. So I reverted back to the igntion side for a breif minute and debated if the new coil that was installed is internally opening when the motor warms up. I swapped a coil off a older vehicle that is similar in style and the boat ran and idled very well. It missed a few times but nothing like it was previously. I am wondering if I had a combination of bad gas and a crappy new coil. I will keep you guys posted with any new out comes! To note I have confirmed it is a 3.0 with a Mercarb on it and not a rochester. Sometimes you have to get dirty and get the information for yourself and not listen to others! LOL. Thanks again fellas!

They make epoxy filled coils for marine use...less internal vibration than cheap oil filled coils. I installed a BLASTER epoxy filled coil and never had a bit of trouble w/it. Make sure you have the correct base gasket for the Mercarb...much thicker than standard base gaskets. It provides for better fuel atomization which greatly improves idle.

Hello All back again, the coil only helped the concern temporairly. It ended up being the ignition B+ wires leading to the coil has been replaced and the wire that was used was to small for the current that was needed and was heating up causing us to lose power intermittently. Just figured I would post the correct information. Thanks

The flaw I see is "Carb was rebuilt".Well,there's the answer.Another one tampering with their carb.Let me guess?You used gumout or other type of carb cleaner on the carb.I see so many people asking questions why their boat engines run poor after rebuilding their carbs.You cleaned a 1986 carb out & installed factory setting's carb kit.Now wondering why the thing won't idle.You followed everything by the book as well now stumped.It's a 1986 carb.Installing factory 1986 parts on a warn,used,aged carb,factory settings won't work.Setting by the ear is the true & only way.Ask any true Harley biker.Also,depends on how many times it's been rebuilt.You can only rebuild a carb so many times before is done.
Another way to explain is,Under your accelerator pump spring is a tiny hole.That tiny hole is molded to fit a ball bearing.Steel ball bearing against aluminum hole & corrosion.aluminum corrosion eats the aluminum surface.We all know aluminum is a soft metal.Aluminum corrosion eats just like teeth decaying.So,what happen's if you clean that ball bearing hole out of a 1986 carb?You just made the hole bigger.The ball bearing isn't factory seated for the size hole anymore.That is the reason,why carbs can only be rebuilt so many times.Until the carb is junk & can't be rebuilt.
When,you buy a carb rebuild kit.It comes with all the goodies.(New factory Neddle valve & seat,Ball bearing & ect),Some even come with new jet screws.Same thing as I explain about the ball bearing hole as well as the jet screw hole/insert."It's made of Aluminum" not with standing hard steel.
To rebuild a carb correctly requires reusing the old ball bearing.Reason?The old ball bearing is warn & cut from ware & tear thru the yrs from 1986.Also,most people don't realize or know there is a ball bearing inside the carb.When ,they remove the carb from the intake.Some turns the carb upside down to either look at it.Or to unhook something.If you turn the carb upside down?The ball bearing will fall out of it's hole.The only thing holding it in is the tiny pressure from the spring.
So,many people are rebuilding their carbs this year.Then,stating engine won't idle or hard to start then,asking the reason why.Because,of incorrect rebuilding the carbs.I hear many people saying this as well,"All boats are cold blooded,hard to start,requires giving it throutle to start it until warmed up"
If your carb is rebuilt correctly,Choke is adjusted correctly and you have fuel & spark?2 -3 throutle pumps that engine should fire right up & stay running on high idle until you kick it down.There is no difference from a boat engine to a car engine.I know a guy that took a Mercruiser 4.3 Liter and installed it into a Pontiac Bonnivlle.Just had to switch over the intake,exhaust manifolds and bolt on the pontiac motor mounts.The engine ran the same in the car as it did in the boat.With very low miles like new.

After typing all of this now I just realize you found your problem wiring.Well enjoy the tip.
Best,