Problems with mercruiser 5.0 lack of power, bogging etc.

[saltwater_cowboy]

Looking at a friends inboard ski boat with the 5.0 mercruiser model MTE230.<br /><br />The boat had not been used for a few years when he got it so we did compression check - 6 @ 150+, 1 @ 140 and 1 @ 130 but the low ones went up with a little oil.<br /><br />Put on new leads, plugs, cap and arm and did a carb rebuild (soaked for a few days, blow out with compressed air) new gaskets etc and float set etc.<br /><br />Starts ok but runs rich (slight black smoke) at tickover no matter how the idle adjustment is set. On acceleration it has the initial pick up (which I assume is the accelerator pump) but quickly bogs down. If I accelerate slowly it splutters and picks up but does not like over 2/3 throttle. <br /><br />At present it doesn't even have the power to pull a skier.<br /><br />So even after a carb rebuild the only thing I can think to do is junk the carb and get a new rebuilt one. Its a quadrjet and I can get a fully rebuilt one on ebay for about $250.<br /><br />Anyone care to offer any advice?<br /><br />Thanks in advance<br /><br />Jay

 

[waterone1@aol.com]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

I noticed that you didn't say anything about fuel filters. You did replace them, right ? Was the gas drained and the tank filled with fresh gas ? A newly rebuilt carb will get gummed up in minutes if it is "drinking" bad gas. Have you also checked the ignition timing ?

 

[vipzach]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Ditto what waterone1 said, check the gas and filters...sounds like water and junk in the fuel. Maybe timing.

 

[saltwater_cowboy]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Checked timing, thats ok. Replaced fuel and filter.<br /><br />Any ideas?

 

[waterone1@aol.com]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Black smoke (not blue) is surely a sign of running rich. I've screwed up a carb rebuild once or twice...maybe you missed something ?

 

[saltwater_cowboy]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

I've had it apart twice now and followed the guide step by step.<br /><br />I first thought that the float level was too high and thats why it ran rich on idle but then I thought that the float level was too low and thats why it runs out of fuel as I accelerate but its set at 1/4" which is correct for my model of carb.

 

[Manipulator]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Check firing order. Last thing I did before I put her in the water was change the plugs. We launch and I take her out to warm her up and I could barely plane her off. At first the idle was a little rough but I figured it was do to being cold and the old gas in the tank. I think my weekend is ruined as I have a boat that has lost a lot of power and it will take all weekend to fix. My dad puts the trailer away and comes over. I explain it to him and first thing he says is firing order. I'm like "dad she idles fine no way it's the firing order". So reluctantly I get the manual out check the firing order. Sure enough I had two cylinders swapped. Basically I had a six cylinder until I swapped them back. After that she ran great. This is my first V8 and I didn't know that it will run on 6-7 cylinders and look fine on an idle. Now I know.

 

[THE BEEF]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Float ---- is it a black plastic one???<br />This will cause all sorts of problems.<br />When thay get old thay will not hold the proper level.Flooding problems run rich etc...<br />Get a brass float and try it before a new carb.<br />Go ask an auto mech about this, I bet he'll tell you horror stories about cars having the same problems<br />when thay ran carbs. plastic is cheaper then brass<br />Demand a BRASS FLOAT 10$ is cheaper then 250$<br />GOOD LUCK!

 

[jeff13601]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

In your original post you said it burned rich no matter how you set the idle screw. Did you mean the air/gas adjustment screw?

 

[saltwater_cowboy]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

The screws are the two screws at the front of the carb that the rebuild manual refers to as idle mixture screws.<br />No matter how these are adjusted it still runs rich.<br /><br />The flaot is a black pastic one but has no holes and is not full of fuel so I can't see how that can be faulty.<br /><br />I'm in the UK so parts for this carb are not easy to come by.<br /><br />The plug leads are connected as per the markings on the inlet manifold and on the dizzy cap.

 

[THE BEEF]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Is the float new ? If not CHANGE IT. The float is solid and very light. Thay wil get saturated with gas and flood engine .Look down carb air horn when this happens and see if fuel is dumping in. I had this problem on a van rebuilt carb no help still flooded BAD FLOAT. Call and ask your marine mechanic.This problem was big in the 70's before<br />FI. On cars anyway.Hope this helps

 

[THE BEEF]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Is the float new ? If not CHANGE IT. The float is solid and very light. They will get saturated with gas and flood engine .Look down carb air horn when this happens and see if fuel is dumping in. I had this problem on a van rebuilt carb no help still flooded BAD FLOAT. Call and ask your marine mechanic.This problem was big in the 70's before<br />FI. On cars anyway.Hope this helps

 

[jeff13601]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Is the black smoke just at start up? It wouldnt account for the smoke, which may be a seperate issue, but maybe you could be starving for fuel. Have you checked the pickup screen in the tank, the vent and the fuel pump pressure?

 

[saltwater_cowboy]

Re: Problems with mercruiser 5.0 lack of power, bogging etc.

Not checked fuel pump pressure but with engine crnking there is a good flow of fuel from the pump.<br /><br />Can't get a new float here in the UK so I'll have to order one from the US.<br /><br />Going to have a nother fiddle at the weekend.