1990 Glastron Sierra Mercruiser 3.0 CARB REBUILD HELP!!!

[Drobinson1389]

Hey Everyone,
I am a new member to I-boats, and just like to say everything i have ever read off of here has been more than helpful. Now i have a problem of my own. I have a 1990
Glastron Sierra Boat with the 3.0 MerCrusier Engine. It is inboard. I have a issue with taking off (pulling someone up out of the water) when i push the gas down to accel it
Wants to die. If i start to Pump the throttle is tries to get going then sometimes does. The Boat Starts right up and ideal just fine. Then once the boat is all warmed up it takes off from a dead stop pretty good!

I have read people doing a carb rebuild and it fixes the problem. I am pretty new to the boat engine world and i am wondering what kit i need to buy and is this something that i can do myself here at home.

ANY HELP is greatly appreciated.

 

[V-Tech]

Re: 1990 Glastron Sierra Mercruiser 3.0 CARB REBUILD HELP!!!

It sounds like the accelerator pump in the carburetor is worn out. Is this a GM engine? Probably is. GM uses a piston type accelerator pump in their Rochester carbs and they wear out fast compared to the diaphram type other manufactures use. Naturally there could be other issues, particularly ignition system related, but what you describe sounds more like a carb issue. To me changing the accelerator pump is easy, but I do not know your abilities. You might be able to purchase just the accelerator pump and the air horn gasket (air horn is the very top third of the carburetor and the gasket I'm talking about goes between the main body of the carb and the air horn) You'll have to take the airhorn off to replace the accelerator pump. You should not need to remove the entire carb from the engine.

Again, I do not know what carb you have. If you can't get just the parts I mentioned you'll have to buy a carb rebuild kit. They might need some numbers off the carb to order you the correct kit.

 

[Drobinson1389]

Re: 1990 Glastron Sierra Mercruiser 3.0 CARB REBUILD HELP!!!

Thanks in advance for the help. I did go ahead and rebuild my carb and that seemed to work out pretty well for a while. I am having a very hard time trying to get the idle right. It seems that i can get it to idle good but then when i put it in gear it barely wants to run, then once it gets warmed up the first slowest setting it seems to run great but as soon as i take it out of gear it seems that it ideals where to high. Does anyone know hoe to get the ideal to be perfect? What am i missing? It ran better before the carb rebuild.

The rebuild also did help with the acceleration problem but sometimes it does like to bog and want to die at take off. Now trying to kill the motor is worse then ever. It will try to keep running even with the key off? Has anyone had this problem or can help me with it?

The boat does seem to run very good though when it warms up. Those are just the issues that i am having and just want to get it figured out so i can winterize the boat before it gets to cold.

Thanks again for all the help!!!!

 

[kd7isf]

Re: 1990 Glastron Sierra Mercruiser 3.0 CARB REBUILD HELP!!!

Hi,

1st, you have what is called a "MERCARB". This is a veriation of a 2bbl Rochester carb that Mercruiser came up with.....
2nd, YES, this IS a GM engine. If you have a 3.0 mercruiser (inboard outboard -- also called a stern drive) then you have a GM Marine 3.0l I-4

Sounds to like you have a couple of problems...

1. Did you replace the float? Most kits come with one and although its a very good idea to replace it, you can't just stick it in and expect it to work.
-You need to set the "Float Level" and "Float Drop". Instructions for this can be found in the manual and in the adults only section of this website under carb rebuild. Use the specs from the mercrusier manual -- not from anywhere else.....
-Not doing so can cause flooding and other problems.

2. You said it worked just fine once the engine warms up. While it is possible that your accellerator pump was worn, most likely your choke was not adjusted correctly. A worn accelerator pump should be noticeable warm and cold.

3. There are 2 steps to setting the idle mixture. You seem to have found one.
-Step 1. Warm the engine up. Bring it down to idle. You may have to adjust the idle stop screw (the one on the throttle linkage) to bring the idle up enough to keep running. Adjust the idle mixture screw (the one sticking out of the carb base) for the fastest idle you can get (better method is to connect a vacuum gauge to the manifold and adjust for maximum vacuum).
-Step 2. Put the boat in the water, tied to a dock. Warm the engine up. Put it in gear (at idle). You may have to adjust the idle stop screw again -- in gear your idle should be around 600 RPM or so -- see specs in the manual. Adjust idle mix screw for highest possible vacuum or idle speed again, adjust idle stop screw for proper idle speed. You may find that when you take it out of gear your idle increases a little. See the manual -- appx 150 RPM increase when shifted to neutral is generally about right...


Hope this helps....

 

[Drobinson1389]

Re: 1990 Glastron Sierra Mercruiser 3.0 CARB REBUILD HELP!!!

Thank you for that information. I did not replace the float as the kit i got did not come with one.I just reused the old one and didn't even adjust it. Do you suggest that i go ahead and purchase a new float and adjust it to the specs on this website. I am fairly new to this type of thing. I am trying to learn everything on my own since i am sick of paying shops to do everything.

I do know where the idle mixture screw is and that is the one that i have been messing with. Now the idle stop screw that you mentioned i have a slight idea, im just trying to make this 100% Clear to me, thats the other screw that i can pretty much barely reach with a short screw driver? Does this deal with my choke adjustment as well? I really am thankful for the help.

I do have a 3.0 Mercrusier Inboard motor. Once again i cant stress enough how thankful i am for all the help.

 

[kd7isf]

Re: 1990 Glastron Sierra Mercruiser 3.0 CARB REBUILD HELP!!!

As long as the float is in good condition, theres no need to replace it... But ALL carb kits (save for gasket only kits) come with a new seat and needle. You will need to adjust the float after installing the new seat and needle...

Yes, the little screw on the throttle linkage that you can barely get a short screw driver to... (NOT the one holding the linkage onto the end of the throttle shaft!! : o ) )

No effect on choke. See the manual. Choke is the round black thing on the front of the carburetor. It opens and closes the choke butterfly (the metal part at the top of the carb that opens and closes).
Manual says how to set it. It should have 2 wires (one connected to the tab on the black part, one connected to one of the 3 screws holding the black part on). On a cool day, the choke should be completely closed with some spring tension -- and open within a few minutes of power being applied to the choke.
There is a mark on the round black part and several marks near the top of the metal housing. These are the index marks. If you have an aftermarket carb, the black part might not have the index mark...
Note: the clymer manual procedure is wrong -- use the mercruiser manual.

This is why we warm the engine up BEFORE making idle adjustments -- choke can cause you to get the adjustments wrong : o )

Hope this helps