3.0 Liter Mercruiser Bogging at full throttle

Hunter37618

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Jun 24, 2013
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I have just purchased a 1999 Stingray with a 3 liter mercruiser engine. There are several issues that could be causing my problem. The first thing I did was to buy a new prop as the old one was bent up. I then took the boat out to try it and it was very slow out of the hole and would only run about 20 mph at 2500 RPM's. I had a guy go through the fuel system, empty all the gas, put a carburetor kit on it, new plugs, distributor, and rotor button. I took the boat back out and at full throttle the boat would not come out of the water. I backed the throttle off to about half and I could hear the RPM's increase slightly and it finally planed out. The boat was running right at 28 mph at 3000 RPM's but nothing happens when I give it more throttle until I push the throttle lever all the way forward then the engine boggs slightly. After running up the lake with no improvement I came back to the dock and the boat would not idle.

Now I removed the spark arrester so I could look into the carburetor and I could see gas dripping into it. I figured the float was stuck causing the engine to load up. I took the carburetor back apart last night and cleaned it very thoroughly and replaced the vent hose (that was dry rotted) running to it. I started the engine on the hose and it is running very smooth now. Before last night the engine would shake slightly while idling and sometimes die. I am going to take the boat back to the lake this evening to try it out.

I guess my question is this: I found out the prop that was installed is too big and I am not sure if that could be keeping the engine from gaining more speed or if the carburetor may have been the entire problem. Any help will be appreciated.
 

eavega

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Re: 3.0 Liter Mercruiser Bogging at full throttle

Since you messed with ignition components, did you verify timing/dwell?

II guess my question is this: I found out the prop that was installed is too big and I am not sure if that could be keeping the engine from gaining more speed or if the carburetor may have been the entire problem.

You could be overpropped and lugging the engine. What size boat do you have it on? What pitch prop do you have on it now? Do you have any history on this boat that would indicate there was a problem prior to replacing the prop?
 

Hunter37618

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Re: 3.0 Liter Mercruiser Bogging at full throttle

Since you messed with ignition components, did you verify timing/dwell?



You could be overpropped and lugging the engine. What size boat do you have it on? What pitch prop do you have on it now? Do you have any history on this boat that would indicate there was a problem prior to replacing the prop?

The boat is a Stingray 180RS which is 18'. The prop that is on it is 14.8 X 17 and I think the boat calls for a 13.9 X 17. I don't really have any history other than the boat has been sitting for 2 years.
 

eavega

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Re: 3.0 Liter Mercruiser Bogging at full throttle

We have very similar boats (1988 Stingray 176 SVB), so I doubt its your prop unless you have some serious underlying issues with saturation/water under the deck. I think I would be borderline underpropped with a 17" Pitch prop.


I will repeat, you need to verify timing, since you were changing/modifying ignition components.

re-addressing the carburetors was also a good idea. If its not ignition/timing related, i would also say its a fuel problem.

Rgds
 

Hunter37618

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Jun 24, 2013
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Re: 3.0 Liter Mercruiser Bogging at full throttle

We have very similar boats (1988 Stingray 176 SVB), so I doubt its your prop unless you have some serious underlying issues with saturation/water under the deck. I think I would be borderline underpropped with a 17" Pitch prop.


I will repeat, you need to verify timing, since you were changing/modifying ignition components.

re-addressing the carburetors was also a good idea. If its not ignition/timing related, i would also say its a fuel problem.

Rgds

I am going to get the timing checked as I have no idea how to nor do I have a timing light.
 

Bondo

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Apr 17, 2002
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Re: 3.0 Liter Mercruiser Bogging at full throttle

I have just purchased a
I am going to get the timing checked as I have no idea how to nor do I have a timing light.

Ayuh,.... There's Really Alota things that really oughta be Checked, by someone who knows I/Os,...

It sounds like it's general overall condition is pretty much Unknown at this point,...

just to get an Idea,... Up in the Adults Only section, at the top of the forum,...
Read through the summerization thread, 'n winterization thread,...
That's generally All the things that need checkin',... Annually,...
 

Hunter37618

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Jun 24, 2013
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Re: 3.0 Liter Mercruiser Bogging at full throttle

Ok I pulled the filter out of the fuel pump and it was nasty to say the least. So I replaced it with a new filter and took it to the lake. The engine started right up and idled perfect. The boat was still a little slow out of the hole but did seem to plane out a little better. I didn't push the throttle all the way forward at first as I wanted to see how the engine sounded and watch the RPM's. This time as I eased the throttle forward past half the engine RPM's did increase to 4300. It did take a few seconds for the RPM's to build up. The engine ran at 4300 RPM's for about 2 or 3 minutes and then slowly decreased down to around 3000 RPM's. My next step is to disconnect all the fuel lines clean or replace them and try it out using an external fuel tank. I found out the guy that had the boat before me was very unhappy when he was told to give the boat back. He cut all the wires under the dash and could have possibly put something into the gas.
 
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