Merc 5.7L bogs slow to plane

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1736p

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May 31, 2004
Messages
3
I have a 1987 Sea Ray Weekender 23ft. When ever I press down on the throttle (to fast) the motor seems to bog down and then picks back up after a few seconds. Or, I can back off on the throttle and ease into it and it doesn't bog so badly. It just seems it is taking forever to plane, especially when I have 5 or 6 people in the boat. 1st.... how can I get it to quit bogging when I go to WOT? (WOT RPMs achieve 4200) 2nd... Would a hydrofoil help plane or a decrease in pitch on the prop? THANKS! Nick
 
W

WSUDERMAN

Petty Officer 2nd Class
Joined
Sep 9, 2001
Messages
176
Re: Merc 5.7L bogs slow to plane

Nick,<br />Just a guess, but it sounds like your accel. pump on the carb. They tend to dry out over the winter and after a few winters - crack. <br />Easy fix if you like wrenching or just get the carb rebuilt.<br /><br />your WOT rpm's @ 4200 are in the range 4200 - 4400. If that was with a full load your current prop is good. If that was with a light load you might be able to go down a notch to increase your rpms to the top of the range.<br /><br />Wes
 
snapperbait

snapperbait

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Aug 20, 2002
Messages
5,754
Re: Merc 5.7L bogs slow to plane

Agree with Fourwinns.. Accellerator pump is a good place to start.. <br /><br />Also check for any slop in the accelerator pump linkage.. Upon moving the throttle even the sligtest bit, you should get a squirt of fuel into the throttle bore, immediately... Sloppy (loose) linkage or a worn acc pump cam can delay the acc. pump shot...<br /><br />5-6 people is quite a load.. A hydrofoil may help seeing as your hitting WOT.. A better way to help with the load would be installing a set of trim tabs (if you don't already have them, of course)....<br /><br />Good luck, and let us know how you make out with the problem...
 
1

1736p

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May 31, 2004
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Re: Merc 5.7L bogs slow to plane

Thanks for the info! I'll check acc pump. About the planing, I have trim tabs already...I ran the boat yesterday and I just hit 4200 WOT with only 2 people in the boat. My current prop is a 15 X 17 RH 4 blade...what is your opinion to achieve WOT 4400, one that is quick to plane I'm not looking for speed just quick out of the hole and a nice cruise @ +/- 25 mph (one that doesn’t call for the 4 barrel to open). I was thinking 16 X 14 3blade or 15.25 X15 three 3blade. Any suggestions. THANKS AGAIN for the info! Nick
 
POINTER94

POINTER94

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Oct 12, 2003
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5,031
Re: Merc 5.7L bogs slow to plane

Nick,<br /><br />I have a comperable boat and I am turning a stainless 14.5 x 17 with a 1988 5.7L and the boat make a touch over 41mph at 4400 rpm. Seems like a good match. I would like to go a bit faster but performance with this is solid. Holeshot, speed to plane, and some tell me that that is a good speed for a 25ft CC.
 
1

1736p

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May 31, 2004
Messages
3
Re: Merc 5.7L bogs slow to plane

Thanks for the prop info, I may give that a try. I just checked the acc pump and sure enough it is only shooting on one side (right side looking at the motor)same side as the pump. Now how do I get it to shoot out on the other? I tried some carb cleaner--no help yet. If I can get it to shoot out of both sides maybe this will solve all my problems! Any sug.. Nick
 
R

Rhadley

Petty Officer 1st Class
Joined
Jul 20, 2003
Messages
219
Re: Merc 5.7L bogs slow to plane

Welcome to the world of BOG. I have a post going on this also, and the problem is very common with many friends I talk to. Bad gas can also cause a problem, but there is a design deficiency in some of the Mercarbs, especially the pre-1987 ones.
 
A

anesthes

Petty Officer 2nd Class
Joined
May 5, 2003
Messages
186
Re: Merc 5.7L bogs slow to plane

mines doing the same thing.. quadrajet. I think the carb is junk.. what else is new.
 
A

anesthes

Petty Officer 2nd Class
Joined
May 5, 2003
Messages
186
Re: Merc 5.7L bogs slow to plane

I was offered a Carter 4V today for $150 (rebuilt carb). I think i'm gonna modify the fuel line, and try that out. See if the boat runs better with it.<br /><br />-- Joe
 
S

steve n carol

Chief Petty Officer
Joined
May 8, 2004
Messages
459
Re: Merc 5.7L bogs slow to plane

Nick, As Captain of your boat, you are responsable for much. Other persons are guests and usally will listen and comply with your suggestions on where to sit, or stand. Move them to places where your boat performs best and they are safest. When I pull skiers, the flag person is able to sit in the seats at the bow, (open bow). this helps me and helps the boat plane quicker. Our guests usally are unaware of such things as plane, list, exposed engine moving parts, and other boating common sense. what was plugging your accl pump?
 
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