Sputtering when going to full throttle

[rkeown]

I have a 1989 NS40C Nissan motor. It starts fine, idles fine, but when I give it gas to take off, it wants to sputter until it gets on plane and then runs great. I've had the carb rebuilt, prop replaced, new plugs and gas. I've replaced all of the hoses thinking it might be sucking air. The motor is pushing a 15 foot figerglas Nissan boat. I notice it more when there's more than one person in the boat. I gapped the plugs at .040. Great running motor other than this one issue. Please advise on what the problem could be.
Thank you.

 

[Sea Rider]

Re: Sputtering when going to full throttle

My engine does the same when not well warmed up, (4 or less minutes) give a full wot for 15 seconds and problem solved. Check gas/oil mixture maybe too much oil, in idle oil tends to paste tip plugs as they have not reach their proper tip temperature to burn oil tip acumulation well.

Hapoy Boating

 

[rkeown]

Re: Sputtering when going to full throttle

Thanks for the reply and suggestions. I tried them with no success. I took the fuel pump appart and found nothing unusual. The diaphram appeared OK, but might be a little stretched. Blew through the ends and one took the air and one didn't. I assumed that the pump was working properly from that small expierment. Took the spark plugs out and they appeared a little fouled, somewhat oily. When I put my passenger way up front to assist in the boat planing out, the problem of the motor sputtering seems to go away. I had fish in the rear livewell the other day and when me and my fishing partner was in the seats, the motor never got on plane. I moved to the bow of the boat and the motor reduced the sputtering and was on plane in no time. The motor runs great with no sputtering on plane. I'm still scratching my head and I really appreciate the suggestions.
Happy Boating,
Richard

 

[BOAT DOCTOR]

Re: Sputtering when going to full throttle

if you can run the motor and when it starts to act up choke the motor does it pickup and run good for a second or so or does it fall on its face?

 

[rkeown]

Re: Sputtering when going to full throttle

Thanks for the question. I tried choking the motor when I was accelerating and the motor was sputtering, and the motor fell on it's face. I changed the gas today and cleaned the plugs. Heading to the lake tonight after all the frolickers head in for some night fishing. I appreciate all of the advise...someday we'll come across a solution.

 

[BOAT DOCTOR]

Re: Sputtering when going to full throttle

take off silencer cover off of carbs when running boat then get motor to act up and choke off each carb one at a time to see what carbwould stop it from sputtering and that will be the carb that has the problem

 

[rkeown]

Re: Sputtering when going to full throttle

My motor only has one carb. I did clean the two plugs and took the fuel pump apart and cleaned everything inside it. The motor runs much quieter now and seems to sputter less on take off's. I guess I'm at a loss for my next step. I do thank everyone that has offered their opinions and advise as to what I might need to check or do.