'98 Merc 4 stroke bigfoot Runs weird.

Seein Stripes

Recruit
Joined
Jan 24, 2002
Messages
5
I bought this motor in August from Florida (salt) and it runs good, but not perfect. It has new plugs, new fuel separator, and doesn't have many hours on it. <br /><br />It cranks up great and usually idles okay, but sometimes it chugs and sputs, sometimes it doesn't. When you make your first run to wherever you're going, it will run 27.0-27.2 on my Lowrance GPS at about 4800 RPM. On subsequent runs after that, it starts off much slower then gradually picks up RPM the farther you go. It will also seem to 'shuffle' back and forth between running clean and wide open to slightly off and about 2-3 mph slower.<br /><br />It has a low water pickup, It's turning a 14p 4 blade stainless surface cutting prop made by Prop Tech, a lot of cup. It's on an 1860 Sea Ark tunnel and is sitting high enough to let it eat some air while running with it trimmed all the way up. <br /><br />Another weird thing is you can't ever hammer the throttle, it will die, you have to baby it until it seems to 'catch' and then you can hammer it at about 2000 RPM. Once it planes out, you can feel that when the throttle is pinned, it's not running at its best at times, and letting off about an inch it will speed up and sound better. After about 5 minutes of running, you can slowly put it back all the way down and it will run fine.<br /><br />I've been told that it's just overpropped, but I feel that it is in the carbeuration. I have run three 12 gal. tanks of carb cleaner including MMO and ValveTec to no avail. Is it mechanic time or should I just put a 90 HP on her?<br /><br />Thanks a million! Shawn.
 

snooks2005

Cadet
Joined
Nov 9, 2002
Messages
25
Re: '98 Merc 4 stroke bigfoot Runs weird.

I have the same engine as was wondering who was the manufacturer of your prop.
 

Seein Stripes

Recruit
Joined
Jan 24, 2002
Messages
5
Re: '98 Merc 4 stroke bigfoot Runs weird.

Snooks, I think the Mfr. is actually "Prop Tech" at least that's what it says on the prop. There's a phone number engraved on it also, I can get it to you if you'd like.
 

DP

Petty Officer 1st Class
Joined
Sep 18, 2001
Messages
209
Re: '98 Merc 4 stroke bigfoot Runs weird.

I have the same engine with the standard lower unit on my BW 17 Montauk. Tops out at 33 mph with a Merc 4 blade Trophy Sport pushing about 1600#s.<br /><br />I had a similar problem and it was found that the carbs were out of sync. Might be wise to take it into a dealer and have them checked.
 
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