RPM's not getting higher than 4,000 on Mercury 4.3l

[viettim]

i have a 2003 Mercury 4.3L V-6 in a Sea Ray 19' and i can't seem to get the engine to pull more than about 4,000 - 4,100 RPM's. it has a quicksilver 4-blade prop. any idea why it isn't hitting the 4400 - 4800 rated rpm limit?

 

[Bondo]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

Ayuh,....

It either needs a Tune Up,... or,.. The Prop is Too Big, drop some pitch....

 

[nlain]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

I have a 2004 SeaRay 185Sport with 4.3L 190hp, Alpha 14X23 Prop, don't remember the gear ratio, I have no trouble getting 4800 even with a full load. I think Bondo hit it pretty good.

 

[MikDee]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

i have a 2003 Mercury 4.3L V-6 in a Sea Ray 19' and i can't seem to get the engine to pull more than about 4,000 - 4,100 RPM's. it has a quicksilver 4-blade prop. any idea why it isn't hitting the 4400 - 4800 rated rpm limit?

A history of the boat would help, did it ever run 4400-4800 before? with any prop? or is this a prop you just recently put on the boat, and now it's not reaching this rpm? and what's the pitch on the 4 blade?

 

[viettim]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

thanks all. not sure if it ever did...i just got the boat a couple of weeks ago. the engine runs great, starts no prob, idles well, etc. i'm not sure the pitch but know it has a quick silver 4-blade prop. i'm thinking the first step is a new prop and then even an fuel intake cleaning would be good. any good suggestions on any additives that work well?

 

[bhammer]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

i have a 2003 Mercury 4.3L V-6 in a Sea Ray 19' and i can't seem to get the engine to pull more than about 4,000 - 4,100 RPM's. it has a quicksilver 4-blade prop. any idea why it isn't hitting the 4400 - 4800 rated rpm limit?

I have a 06 4.3 MPI @ 220HP and have to run a 17" 3 blade to get to my RPM. Boat manufacturer sold them with 18" 4 blade but could never get WOT.

 

[wca_tim]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

try looking at the prop for markings. May have to remove the prop nut to see them on the rear of the hub. Unless it is higher than a 23 or so, i would bet that you're in need of at least a full tune up (not just fuel additive... plugs, cap, wires, fuel filter, check and clean everything, etc, etc, etc...

my 4.3 in an 18 foot boat would turn a 26" prop to 4700... and 23 to 4800-4900, 21 4 blade to over 5000. I'm assuming that your boat is fairly light and that you don't have a monster mismatched prop on there. can't be sure until we know a little more... at least what the current prop is.

Cheers!

 

[bhammer]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

try looking at the prop for markings. May have to remove the prop nut to see them on the rear of the hub. Unless it is higher than a 23 or so, i would bet that you're in need of at least a full tune up (not just fuel additive... plugs, cap, wires, fuel filter, check and clean everything, etc, etc, etc...

my 4.3 in an 18 foot boat would turn a 26" prop to 4700... and 23 to 4800-4900, 21 4 blade to over 5000. I'm assuming that your boat is fairly light and that you don't have a monster mismatched prop on there. can't be sure until we know a little more... at least what the current prop is.

Cheers!

Wow, what drive ratio do you have? I only wish I could get that out of my 220HP. Now, I do have a 3000# boat and I am sure that has some to do with it. Sorry to get away from teh OP.....

 

[viettim]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

thanks everyone. i am putting on a 14/24 3-blad prop to get back more to stock. i'll take it out next weekend and see if that's the ticket.

 

[MikDee]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

thanks everyone. i am putting on a 14/24 3-blad prop to get back more to stock. i'll take it out next weekend and see if that's the ticket.

That sounds like way too much pitch for that boat combo! I'd say maybe a 19", or 21" pitch, max,,,, You really need to find out whats on there first before you go, and throw anything on. Usually, one step up in pitch is required with less blades, so if it was an 18" pitch 4 blade, a 19" pitch 3 blade would be in order.

 

[viettim]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

that's good advice, i found a guy who is willing to let me try a few before i buy. sounds like that's the way to go. what about stainless vs aluminum?

 

[MikDee]

Re: RPM's not getting higher than 4,000 on Mercury 4.3l

that's good advice, i found a guy who is willing to let me try a few before i buy. sounds like that's the way to go. what about stainless vs aluminum?

IMO, stainless don't spool up as fast as aluminum, (it works your engine more) but holds steady fixed speed like a rock, will give you more top speed because it's rigid, and can be run higher out of the water, especially when trimming, but it's heavier.