Weber Redline carb performance for 3.0L Mercruiser

AR185

AR185

New Member
Jul 13, 2009
35
Mobile, AL
Boat Info
185 Sport 2007
Engines
3.0l Mercruiser 135 hp
Does anyone have any experience with the Weber Redline performance carburetor for the 3.0L Mercruiser?

http://www.alamomotorsports.com/weber/mercruiser.html

http://www.redlineweber.com/html/application_guide/mercury_cruiser_6_4_1_performanc.htm

I'm interested in finding out if this upgrade is worth the cost.

The claims are enticing:
"
Performance Kit Features:
¨ Improved Idle quality:
Aids in low speed maneuvers, docking, picking up skiers, fishing
¨ Improved fuel economy:
More miles per fill-up, less expensive to operate, burns fuel efficiently, engine starts easier
¨ Horsepower & Torque output increased up to 21%:
Pull Skiers up easier, come to plane sooner, Max RPM increase"
¨ Complies with:
“Recreational Boating Safety Regulations”
“Code of Federal Regulations” CFR 183 Subpart J, Carburetors
“United States Coast Guard"
 
I'd be interested to find out myself. I had a Weber 32/36 on a 1977 Toyota Celica after I removed the pr of Side draft 48mm Webers that were on there and mpg went up, but lets just say I nneded a horn after that. The 48's had no air filters just chicken wire over the air horns!!!! Didnt need a beep beep with those.:grin:

Scared many jay walkers in those days.
 
No personal experience with that carb, but I have done a fair amount of carb work. I don't think you would see many benefits. also, then you deviate from OEM equip, which may come back to bite you down the road. If your current carb is working well, which I am sure it is, I doubt that you would see any noticable improvements. Now getting a 4.3, that would make a huge difference :)
 
What about not having the oem carb would bite me in the but when it comes to servicing, considering the boat is out of warranty?

The Weber people won't make exact claims on HP, torque etc improvements. They sent me a personal email and said with the 3.0 Mercruiser, I could expect better fuel economy, better tall around performance, and a much smoother idle. They said I could return it if I am not satisfied.

With the satisfaction guarantee, it seems like it would be worth trying.
 
The Weber people won't make exact claims on HP, torque etc
Click to expand...

There is a reason for that. If you have a good working carb now, a new one isn't going to do much for you unless the current carb is undersized or a very poor design. The OEM carb is well designed and sized about right, IMO. The people that will see those big gains needed a carb rebuild.
 
BarryCF said:
There is a reason for that. If you have a good working carb now, a new one isn't going to do much for you unless the current carb is undersized or a very poor design. The OEM carb is well designed and sized about right, IMO. The people that will see those big gains needed a carb rebuild.
Click to expand...

I agree, but if you really want one, get it and let us know what improvements you get. Make sure to document it also, like what rpm's you run at certain speeds and what WOT speed is.
 
Is there any way of getting more power from my 3.0? I know there isn’t a great deal you can do with them but wanted to know if there is a possibility?
Regards
Mike
 
We have a 3.0 Mercruiser I/O in the 2005 18’ Maxum my kids use and it is a quick little boat. Never tried pulling water skiers with it or anything but with 4 of us on it the thing still has a great hole shot.
The motor idles super rough until warmed up, but I’ve learned this is normal for the 3.0.
I did have the carb rebuilt last year when I installed a new OEM exhaust/intake which made it a very little bit more responsive, but it wasn’t too bad before.
We still run an aluminum prop on it because it’s shallow around here and don’t want to take the chance of the kids banging the bottom with a stainless prop.
Your boat is probably basically the same.
I’d check the condition of your prop, basic tuneup stuff, etc. first then go from there.
 
JVM225 said:
We have a 3.0 Mercruiser I/O in the 2005 18’ Maxum my kids use and it is a quick little boat. Never tried pulling water skiers with it or anything but with 4 of us on it the thing still has a great hole shot.
The motor idles super rough until warmed up, but I’ve learned this is normal for the 3.0.
I did have the carb rebuilt last year when I installed a new OEM exhaust/intake which made it a very little bit more responsive, but it wasn’t too bad before.
We still run an aluminum prop on it because it’s shallow around here and don’t want to take the chance of the kids banging the bottom with a stainless prop.
Your boat is probably basically the same.
I’d check the condition of your prop, basic tuneup stuff, etc. first then go from there.
Click to expand...
Thanks for the
JVM225 said:
We have a 3.0 Mercruiser I/O in the 2005 18’ Maxum my kids use and it is a quick little boat. Never tried pulling water skiers with it or anything but with 4 of us on it the thing still has a great hole shot.
The motor idles super rough until warmed up, but I’ve learned this is normal for the 3.0.
I did have the carb rebuilt last year when I installed a new OEM exhaust/intake which made it a very little bit more responsive, but it wasn’t too bad before.
We still run an aluminum prop on it because it’s shallow around here and don’t want to take the chance of the kids banging the bottom with a stainless prop.
Your boat is probably basically the same.
I’d check the condition of your prop, basic tuneup stuff, etc. first then go from there.
Click to expand...
hi thanks for the reply! I have done all the things you’ve suggested. Carb rebuild, dizzy and leads plugs etc ! Think the carb needs setting properly ie mixture and idle. But find it strange that there isn’t anything out there to make the 3.0 faster? Example a Carb upgrade etc
 
Probably a couple of reasons you don't see a lot of aftermarket performance upgrades for marine engines:
  • It takes a lot of HP to increase speed on a boat and not just HP, but low RPM torque.
  • Demand and volume - how many people are going to buy kits for their boat engine to get 3-5mph on the top end vs the car market?
  • The biggest improvements you can make on a boat are things like propellers and trim tabs.
  • If you are looking for the big increase like you might find by tweaking things in a car motor, it's just not there.
There are two old sayings in the boat world, not trying to be cute, but these are so true:
  • "There is no replacement for displacement." That 4cylinder supercharged 400hp rocket engine in a little sports car is not going to translate into similar performance in a boat - the HP is generated at a high RPM and low torque compared to V8.
  • "Want to make your boat go faster - get a faster boat."
So on your 3.0 - which is a great simple, solid motor - you might get a little better performance out of a new carburetor, possible easier starting and smoother idle, but I doubt it is worth the cost. It's a 4 cylinder that produces 130hp, the motor design has been around for at least 40yrs, they are inherently loud and shake a lot, it's just not going to do much more. I'm not saying don't try the new carburetor - they will take it back so why not - but I would not have high expectations. Focus on the propeller and maybe smart tabs, that is where you are going to see improvements.

Let me give you an example - years ago I had a Correct Craft Ski Tique - 16ft boat with a 235hp Commander 302 - we had that boat running and propped perfect - smooth as it could be, 4800rpm at WOT - 45mph was all it would do - and it would do that empty or with two skiers and a boat load of people. A friend had the same boat, they were also into racing cars so he decides to put a 380hp 454 in his. Guess what - top speed on his boat - 50mph - now part of this is the design of the boats, these were inboard ski boats built for water sports not speed. But the point is, he added close to 150hp and only got another 5mph. But he had fun doing it and that was his purpose - ultimately put the 302 back in it.
 
BillK2632 said:
Probably a couple of reasons you don't see a lot of aftermarket performance upgrades for marine engines:
  • It takes a lot of HP to increase speed on a boat and not just HP, but low RPM torque.
  • Demand and volume - how many people are going to buy kits for their boat engine to get 3-5mph on the top end vs the car market?
  • The biggest improvements you can make on a boat are things like propellers and trim tabs.
  • If you are looking for the big increase like you might find by tweaking things in a car motor, it's just not there.
There are two old sayings in the boat world, not trying to be cute, but these are so true:
  • "There is no replacement for displacement." That 4cylinder supercharged 400hp rocket engine in a little sports car is not going to translate into similar performance in a boat - the HP is generated at a high RPM and low torque compared to V8.
  • "Want to make your boat go faster - get a faster boat."
So on your 3.0 - which is a great simple, solid motor - you might get a little better performance out of a new carburetor, possible easier starting and smoother idle, but I doubt it is worth the cost. It's a 4 cylinder that produces 130hp, the motor design has been around for at least 40yrs, they are inherently loud and shake a lot, it's just not going to do much more. I'm not saying don't try the new carburetor - they will take it back so why not - but I would not have high expectations. Focus on the propeller and maybe smart tabs, that is where you are going to see improvements.

Let me give you an example - years ago I had a Correct Craft Ski Tique - 16ft boat with a 235hp Commander 302 - we had that boat running and propped perfect - smooth as it could be, 4800rpm at WOT - 45mph was all it would do - and it would do that empty or with two skiers and a boat load of people. A friend had the same boat, they were also into racing cars so he decides to put a 380hp 454 in his. Guess what - top speed on his boat - 50mph - now part of this is the design of the boats, these were inboard ski boats built for water sports not speed. But the point is, he added close to 150hp and only got another 5mph. But he had fun doing it and that was his purpose - ultimately put the 302 back in it.
Click to expand...
Great advice!
Thanks again. Last weekend I fitted Nauticus smart tabs and did see a big improvement! So I think I’m just going to concentrate on getting the carb set up correctly and look at props! Not sure what prop is on it as it has no numbers! All it says is rapture and it’s a 3 blade stainless steel.
Thanks
Mike
 
Agree with Bill!
Since you’ve already had the carb done the next thing to check would be the prop.
Check to see what you have (pitch and diameter), then figure out what you want to achieve.
Is it the hole shot that you aren’t happy with or the top end speed?
Nothing you can do about the loud rough idle though. That’s the nature of the beast.
Talk to a good prop guy and see what they say.
I had great luck with PROP MD when I was looking to improve the hole shot on my old 300 Sundancer. Their recommendation was right on the money and made a huge difference. It felt like a completely different boat.
Their prices were great too.
Google them and give them a call.
 
Great advice thanks again!
Will try and determine what the spec of the prop is
 
Do you think it would be possible to swap my 3.0 for a 4.3? As the v6 sits a lot lower than the 4 cylinder!
 
Mike 180 said:
Do you think it would be possible to swap my 3.0 for a 4.3? As the v6 sits a lot lower than the 4 cylinder!
Click to expand...

Yes. We know of someone who has one with a 4.3. But you would have to also change the drive because of a different gear ratio.
But unless you’re due for a repowered because the 3.0 is tired or something it probably isn’t worth what it would cost you to buy a complete 4.3 and the proper drive. Not sure that you would get that much of a performance boost since the 4.3 will weigh more.
Probably better off just selling your current boat and buying someth8ng with the performance you’re looking for.
 
Can anyone tell me the best way to set up my carb for max power! It runs very lumpy and doesn’t idle well! Just had it rebuilt and still not great and I’m lucky if I get 35 mph flat out at 4000 rpm!
 
Ps can you please tell me which is the best prop for my boat for speed
Thanks
 
The WOT RPM range for that motor is 4400-4800rpm, so whatever you change with the propeller you want to make sure you stay in that range. Your current WOT of 4000rpm is too low, bad for performance and bad for the motor. Also understand that propellers are measured based on pitch and to some degree diameter. Higher the pitch and diameter the lower the engine RPMs and (to a point) the higher the speed, but lower out of the hole performance.. Lower the pitch and the RPM's go up and the speed goes down - but out of the hole performance is better. Compare it to shifting gears in a manual transmission car only it is hard to shift gears (change the prop).

Pitch is the the distance the propeller would move the boat in one revolution, assuming no slippage. IE a 21 pitch propeller would move the boat 21" for each revolution.

Example, on my boat I have two propellers:
14" x 23" - a 23 pitch propeller. WOT 4500rpm, top speed 48-49mph.
14.25" x 21" - a 21 pitch propeller. WOT 4900rpm, top speed 45-46mph.
I generally run the 21p, but occasionally use the 23.

The 3 blade propellers like you see on most Mercruiser Alpha outdrives are pitched in odd numbers (I don't know why) 17,19,21,23 and are either 14" 14.50 in diameter. A good rule of thumb is for each 1" of pitch change the RPMs change by 200. So go from a 17 > 19 RPMs decrease by about 400 etc.

On small lower HP boats like yours and mine, there really is no benefit to stainless steel propellers, I would stick with aluminum, you can by 2 or 3 for the cost of one stainless steel.

I am guessing you have a 14.25 x 21 on your boat now and assuming it is in good condition, if not that could be your problem. But, if the prop is in good shape and if it is really only turning 4000 rpm and you feel it is running correctly, I would go down to a 19 maybe even 17 in pitch. You want to be able to run at the top of the RPM range. Your best bet is to find a dealer or prop shop that will let you try out a few different propellers before you buy it.
 
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