Mercuiser 3.0L 1989 120 Carb issue

[Dizzi]

OK, I have done my homework and reviewed many of the old threads on this 120 carb. So, I am going to throw this question out there for one of you who are much wiser than myself.

Here are the details, 1989 20ft Sea Ray with 4cyl 3.0L Alpha One engine. It is my fathers boat but I know it well. I know that this engine has a great long tried and true history within the marine world but, I also know that in 1990 Sea Ray went to the V6 in this class of boat. That being said, this boat has very few hours on it and is like new. It is very sluggish out on it's hole shot and if you are trying pull an in experienced skier out of the water by the time the engine's RPM picks up the skier is aready face down. This has been an issue since it was brand new. I was told that Mercuiser had a lot of problems with this engine bogging down on hole shot and was told that there was a Service Bullitin for the POWER VALVE to be replaced? I could not find anything on this, but what I did find was the Accelerator Pump Linkage could be replaced to give you a different set of holes for adjustment.

Does anyone know anything about the Power Valve or the Accelerator Pump Linkage replacments? I know that if he put larger jets in that this may help but I am not to keen on that one.

any info you can give me would be great. You all have always been great!

thanks

Dan

 

[JustJason]

Re: Mercuiser 3.0L 1989 120 Carb issue

Me thinks your problem is an underpowered boat, and nothing to do with the carb.
If your going to do a lot of watersports you should seriously condisder a 4 bladed towing prop. You won't get the same top end out of the motor but it will perform better towing and with heavier loads.

 

[Dizzi]

Re: Mercuiser 3.0L 1989 120 Carb issue

You are correct about that. However this boat is what it is. We put a different pitch prop on when we ski with it and that helpped of course but the bogging down still persisted. So we even purchased one of those ajustable props and tried different degrees of pitch. The only thing we have not tried is a 4 blade prop. But I would still like to know if anyone can answer my questions about the accelerator pump linkage or power valve replacment bullitins? Any help would be great.

thanks
Dan

 

[JustJason]

Re: Mercuiser 3.0L 1989 120 Carb issue

There's no power valve in a rochester 2gc. As far as the acc pump adjustment. On some you bend the rod, on others there are holes you can move the pump rod to. Or it's a combination of both.
The problem is. Where the rod should be set with a light load and with a heavy load are going to be 2 different things to get rid of the bog. You'll have to find a happy medium.

When your towing your trying to pull a truck uphill with it's ebrake on with a lawnmower engine. Changing the pitch on a 3 blader isn't really going to improve towing all that much. You need more surface area on the prop.

 

[Dizzi]

Re: Mercuiser 3.0L 1989 120 Carb issue

Sounds good I will let him know.