Mercruiser bogs down when warm

[boatnbill]

I have an 89 mercruiser alpha 1 with 4.3 litre mercarb gm engine and everything is fine until it gets warm then I have to run it at idle all the way home because it wont get up on a plane without stalling or bogging down. Fuel filters are clean.

 

[Robj]

Re: Mercruiser bogs down when warm

It sounds like a carb problem and/or bad vacuum leak somewhere. I would start by checking for vacuum leaks, if that is OK, then I would rebuild the carb.

It sounds like your problem starts when the engine is warm and the choke is off. My guess it runs OK when cold because the choke is on and the engine is running rich.

I am sure the experts will chime in soon with more advice.

Have a great day,

Rob.

 

[boatnbill]

Re: Mercruiser bogs down when warm

Thanks I'll give it a try.

 

[Don S]

Re: Mercruiser bogs down when warm

http://forums.iboats.com/showthread.php?t=167561

 

[boatnbill]

Re: Mercruiser bogs down when warm

http://forums.iboats.com/showthread.php?t=167561

ordered a rebuild kit for carb, strange thing it usually doesn't stall just cuts out until i reduce to idle then idles fine and will speed up smoothly for a couple seconds then feels like i run out of gas so back to idle all the way home.

Dealer said might also be ignition amplifier or sensor in dist. I removed dist cap and seen a little build up on the posts inside how can the rotor be removed? it seems stuck on and when I pry on the 6 metal legs they want to bend. wouldn't it not start if it was a bad ignition.

 

[boatnbill]

Re: Mercruiser bogs down when warm

ordered a rebuild kit for carb, strange thing it usually doesn't stall just cuts out until i reduce to idle then idles fine and will speed up smoothly for a couple seconds then feels like i run out of gas so back to idle all the way home.

Dealer said might also be ignition amplifier or sensor in dist. I removed dist cap and seen a little build up on the posts inside how can the rotor be removed? it seems stuck on and when I pry on the 6 metal legs they want to bend. wouldn't it not start if it was a bad ignition.

also choke is stuck open all the time so if it was rich wouldn't it run rough at idle when warm?

 

[Maclin]

Re: Mercruiser bogs down when warm

I removed dist cap and seen a little build up on the posts inside how can the rotor be removed? it seems stuck on and when I pry on the 6 metal legs they want to bend. wouldn't it not start if it was a bad ignition.

When was the last full tuneup with all new parts? dist. cap, rotor, plugs, points if it has them and dwell/timing set, etc....

 

[Maclin]

Re: Mercruiser bogs down when warm

Sorry about my standard answer on the tuneup list, you described electronic ignition so no points. The sensor inside the dist. can act like that. Also a coil can show the same symptoms. When this happens if you could get a dwell meter on it just to see if it flakes out as the rpm's rise could be a help in diagnosis (carb vs. electrical). Also try to notice the tach behavior.

How long do you have to wait before it runs normally again? Will it always start and idle when this happens, just no RPM?

 

[boatnbill]

Re: Mercruiser bogs down when warm

First of all thanks a million for the help.

8 years since last tune up 50 hours a year on boat. Tach is dead maybe the coil killed it?

Starts right up and idles fine when it happens I try to sneak up on a plane and almost get there but then it will bog down some times right away sometimes up on a plane.

As far as I can tell its not better till the next day when the motor is cool to the touch.

 

[sarantis]

Re: Mercruiser bogs down when warm

i had the same problem and it cost me a lot to learn not to unerestimate the simplest things.USE AN EXTERNALTANK to eliminate the first and very possible ocassion.Current doesn't get pissed from 2000rpm to 3000rpm.Do not touch the carb unless you are sure the problem is there..Nobody assures you that if you rebuilt it it wil become perfect,so you may cause a combination of problems that will be much more difficult to get solved.

 

[Maclin]

Re: Mercruiser bogs down when warm

It is certainly due for at least new cap and rotor and sparkplugs. Replace those and try again.

If it still happens then I would try the external fuel line and tank.

If it still happens then I would put in a new coil.

If it still happens then it almost has to be the sensor inside the distributor.

 

[boatnbill]

Re: Mercruiser bogs down when warm

Once again I appreciate the support and will try all of your ideas next week. Let you know how i make out.

 

[boatnbill]

Re: Mercruiser bogs down when warm

sarantis sarantis my hero I am forever in your debt, the external tank run like a champ!