'89 Mercruiser 4.3 Bogs in midrange, Runs great idle and WOT

[Tanker_01]

I have a '89 Merc 4.3 with the 3304-9565 Rochester Carb on it. The boat starts cold great and idles perfectly. Once warmed up if I slowly increase throttle it starts to bog and will die around 10-20% throttle. If I push it past 20% up to like 60% it will catch and rev up. It runs at WOT perfectly fine. Another possibly related issue to this is when the motor is hot it does not want to start right up, I have to give it a pump or two and as long as I dont flood it then it will stumble for a second then start up and idle. If I flood it then it absolutely will not start unless I let it air out or spray starter fluid. Does this just sound like I need a good carb cleaning? Clogged jet maybe? I have a rebuild kit on the way now for it but I wanted to pick the brains of the experts before I dug into this. I have extensive experience with motorcycle carbs but this is my first automotive style carb.

Also, side question, do I need to remove the carb fully to refresh it or can everything be done with it installed on the intake?

 

[BruceK]

Drop something into the manifold and you'll have a big headache. I said previously it sounds like you are running rich. Find the cause. Do you have an automatic choke? Check it. I had the Mercarb 2BBL and if it was a Rochester or not I cant comment. It 's bogging issues was often down to the accelerator pump. There were 3 positions you could set it to alter the metered dose. Also have you set the pilot jet correctly?
If your Rochester is the Mercarb 2BBL I can email you the manual for it. PM me an address, if the upload hasn't worked

 

[ARE]

4bl Rochester carbs are very temperamental, the best option is a Holley carb and a Edelbrock inlet manifold combo.