Bog on takeoff

[swandogg]

I have a 85 Rinker I/O with the Merc 120 in it. I had this very annoying bog when trying to takeoff from a stand still and after reading on here that the carb was a very well known issue I placed an order for a few things.
So I ordered new plugs, fuel filter, electronic ignition conversion since I was tired of dealing with points and a carb rebuild kit.
I figured I would do all these before I rebuilt the carb. The engine has never run better. Idles at 800 rpm, WOT is 3000, timing is 8*BTDC which is spec. and the engine is just plain smooth. I took it out and I still get a slight hesitation every once in a great while.
Now is there something else I should look into because I don't want to rebuild the carb if it is not needed. Any suggestions where to go from here?

 

[superbenk]

Re: Bog on takeoff

Check fuel delivery system from the tank through the carb. I found my anti-siphon valve was a problem for me (valve on the tank in the pickup line.

Have you changed your fuel filters yet?

 

[swandogg]

Re: Bog on takeoff

Check fuel delivery system from the tank through the carb. I found my anti-siphon valve was a problem for me (valve on the tank in the pickup line.

Have you changed your fuel filters yet?

Thanks for the suggestion.
Yes I changed the filter. All what I changed is in my original post.

 

[6meter]

Re: Bog on takeoff

I could be wrong, more of a V8 guy, but 3000 seems low for WOT. I'm thinking it should be in the 4's. Redo the carb.

 

[Bifflefan]

Re: Bog on takeoff

accelerator pump in the carb, or a timing advance issue.

 

[swandogg]

Re: Bog on takeoff

I could be wrong, more of a V8 guy, but 3000 seems low for WOT. I'm thinking it should be in the 4's. Redo the carb.

I believe that is what the service manual says. I'll have to double check today.

accelerator pump in the carb, or a timing advance issue.

How would I go about checking and knowing it is the accelerator pump? Is that when I look down the carb looking for two steady jets of fuel?

This is such a sporadic issue it doesn't seem worth it to rebuild the carb right now. Meaning I can not duplicate the problem on my own. It just happens one out of ten times when taking off full throttle.
It is just amazing the difference in the boat in the few things I did do so far.

Thanks for the suggestions.

 

[cr2k]

Re: Bog on takeoff

You can spend hours on here asking everyone and most of us will tell you to take a few hours and rebuild the carb. About the only other thing is the advance in the distributer. Pull the cap and see if you can twist the rotor about 10 degrees. That is the centrifugal advance. If it is stuck you will need to pull the breaker plate and clean and lube the cams.