When I punch the throttle from idle to full, the motor hesitates before it aprings to life.

Occassionally, it will bog down and I have to back off. If I don't back off it will choke out and die. If I ease up to 1/2 or 3/4, it's fine and I can punch it the rest of the way.

It always hesitates but the bog down seems to happen mostly after idling for a while. The problem seems to lessen with fresh gas/the fuller the tank is. The boat is outside kept in a boat slip and I have forgotten to screw in the gas vent a few times. Could it be moisture in the gas?

Boat always fires on first try without choke. Electrical is fine. Spark on all 3 cyl. Compression fine. Everything is otherwise fine. Motor is an 84 Mariner 70hp.

If it's a carbed engine, drain your float bowls, first. Then put a little seafoam in the fuel. 'Might be a little water in there. That's where I'd start. Then I'd inspect my fuel line for internal desinigration ( sp?) due to ethanol.

I would check the Sync of the carbs.

If it's carbed, the low speed jets are probably set too lean.

Yes, the motor is double-carbed. Draining the bowls and checking the lines is a piece of cake. How do I check the synch and adjust the low speed jets?

I had that problem last year and if was the spark plugs. My problem was similar b

I haven't checked my plugs in a while. I'll get down there and give them a look tomorrow. They're the flat type (not sure what they're called), so I'm not sure if that changes anything.

surface gap plugs are great for running at high speed a lot but have a tendacy to fou; out very easily when idling. if its a omc engine run a regular spark plug l77jc4 and it will probably solve your hole shot problem. year, model manufacturer?

I didn't get a chance to get in the water and pull the cowling to check the plugs. I didn't get home from work until just as the sun was going down. No OMC here. The motor is an '84 Mariner 70hp.

Anytime an engine baughs on holeshot, It is a fuel starvation problem. Three things can cause the probem, 1. air/fuel mixture screw is too lean, 2. Carb float set incorrect,, 3. low fuel pressure. You mentioned it happens more at idle. If that engine is the three cylinder model with the single fuel pump. I would 1st increase the air fuel mixture screw from 1.5 turns out to 1.75 turns out and take it for a test run. If that does not cure the problem, rebuild the fuel pump. Simple to do and extremely inexpensive.

Thanks Mike! Yes, it is the 3-cyl model.

Once I am at speed, the motor runs like a champ. It always fires right up; hot or cold.

However, in addition to what I have already stated, it doesn't seem to like to idle for periods of time and will choke out and die if I don't occasionally put it in gear and give it some gas; especially if I don't make sure that the motor is leveled out. I always thought it was just a quirk to my motor and I have learned how to avoid it, but after talking about fuel starvation and such, perhaps this information could be in correlation.

Plugs checked out fine. Backed off the carbs about 1/8th of a turn and the motor came to life! No more bogging (so far)... and I also picked up an extra 1mph on the top end somehow. Not enough fuel to really push the motor maybe?