79 omc 230hp 305 chevy bogging down

[jasonrandolph]

Hello,

After 20-30 minutes going 3,000 rpms with no problems, my boat will bog down if I back off on the troddle. If I try and throddle up, there is no response and it will eventually stall. In order for me to get it started again, I must start it in neutral with the throddle forward and bring it back was It has started. I have limp back to the dock with my fingers crossed.
I have replaced the alternator, and rebuild the quadrajet last year. I went through the fuel system last year and checked the usual suspects(siphon valve, new filter, etc.) Does anybody have any other ideas? Getting frustrated, and don't want to spend another summer without the enjoyment of my boat. Thank you.

Jason

 

[Glastron_V210]

Re: 79 omc 230hp 305 chevy bogging down

I think you were on the right track with fuel.

Try to isolate the fuel system from the carb. Try this:

Get a kicker fuel tank and hook it up to the fuel pump. Cap the line from the main tank so it won't leak. Same problem? If yes, then your main tank and feed line are likely ok. and you have carb/fuel pump problems.

Install a fuel pressure gauge between the carb and the pump. If the pressure doesn't drop off, it's the carb. If it does, it's the pump.

Or, just try a new fuel pump and consider the cost diagnostic. Then you have a spare if it's not the issue which is kinda nice.

I've seen fluky problems when the filter is not completely sealed too. If it's not, the fuel pump will suck air into the fuel line and strange things can happen.

Good luck,

Chay

 

[Howard Sterndrive]

Re: 79 omc 230hp 305 chevy bogging down

After 20-30 minutes

the time - heat thing makes me think vapour lock

Try running with the bilge blower on

 

[jasonrandolph]

Re: 79 omc 230hp 305 chevy bogging down

Thanks for the replies. WIll running the boat with the blower on all of the time cure a vapor lock? I guess I did turn the blower on after it stalled the first time and it ran well again for a couple of minutes then gradually lost power again.
I guess I will spend Memorial day working on the boat vs. enjoying the boat. Again, thanks for the ideas.

 

[jasonrandolph]

Re: 79 omc 230hp 305 chevy bogging down

I ran a boat side fuel test, and everything came out ok as far as pressure and suction goes. The reading suggest that the pump is fine and there are no restrictions. What I have noticed is that the clear hose I used would never fill up totally with gas. Is the line supposed to be full? I did see alot of air and a trickle of gas would come through. I did check all of the fittings and everything was tight. Can someone tell me how I remove the fuel intake out of the gas tank? There is an L shaped fitting going into the gas tank, but it appears to be welded. I don't want to try and screw it out and risk breaking it off of the tank. I have removed the anti-siphon valve from it though.
The reason I am doing this is that it appears that I have alot of Junk in my tank. The fuel filter had debris as well as the small filter in front of the carb. I want to pull the inlet hose and check/remove the screen. Is there anyone familiar with this who can give me advice?
Thank you,

Jason

 

[MikDee]

Re: 79 omc 230hp 305 chevy bogging down

No one wants to tell you to try unscrewing the fitting, with out being able to tell if it's removable, but maybe you can take a picture of the fitting on the tank, a clear close up would be good, and post it for us to help you determine what to do. This does seem like it could be your bottleneck though.

 

[jasonrandolph]

Re: 79 omc 230hp 305 chevy bogging down

Ok, I did get the fitting removed from the tank. Am I incorrect in assuming that the fuel intake line should be attached to this fitting? If I am incorrect, how do I remove the fuel inlet hose to see if it is plugged. Again, thanks for everyones help. Jason

 

[fparkell]

Re: 79 omc 230hp 305 chevy bogging down

Take this for what it is worth;

I had a very similar problem with a same vintage engine. My engine is a 305 chevy mercruiser with a rochester 2bbl carb. I rebuilt the carb and continued to have back fire problems, etc. I then checked the choke and found that the choke was out of adjustment and would slowly close causing the engine to flood. After adjusting choke and resetting idle screws engine is running great.

Choke adjsutment on a rochester carb is done by loosening three external screws and rotating the housing so that the internal tang either compresses or loosens the choke spring. If the spring is too tight the carb pulls too much fuel into the carb, if it is set too loose, the carb will not choke when starting cold.

I dont know if your choke adjusts the same way but it turned out to be a very simple fix to a perplexing problem.

Good luck

 

[jasonrandolph]

Re: 79 omc 230hp 305 chevy bogging down

Thanks for the reply. I will look into the Choke. I did rebuild the 4bbl q-jet last year, but used the old choke. Does anybody have any information about the in-tank fuel pick up?

 

[jasonrandolph]

Re: 79 omc 230hp 305 chevy bogging down

Hello all,

Am I to assume that the fuel pick up is unserviceable if it does not come out with the L shaped fitting on this aluminum tank? From the looks of it, the opening is to small for the pick up tube to be removed. Is this commom with older aluminum tanks. I am at a loss. I have heard of people using comressed air to clear a clogged p/u tube. But I assume this is a temporary fix.