Should I get my props labbed and polished?
 

I've lost 3 - 4 mph on my 502 since I bought my Cobalt 2 years ago and the only really thing I can think that has happened is my props aren't running true anymore.

I just got done replacing manifolds and exhaust collectors on the boat and in the process I yanked the catalyst. I know I'm not really gaining any significant performance with those changes but should I consider labbing and polishing the props on my B3?

If so, anybody know any reputable lab shops in the Tampa area? And should I ask them to try and get me another 200 RPM? Or add some cup?

Unless the props are damaged, I doubt that is the cause for 3-4mph loss. Have you lost rpm at WOT??

I would look toward the health of engine first. Do a leak down test.
Second, check for hook in the bottom of the hull.

I would PM 12meterjoe on here. He is designing and testing some new props.

as griff said,new props are not the answer,sounds to me like the boat is down on power,new props will only confuse him more.

I'm about 4600 RPM at WOT

What we're you Before? Do you have a lot of stuff that has collected on the boat and adds weight? Have you changed plugs, fuel filter Etc? What does the prop look Like?

Padraig

does the boat stay in the water or on a trailer?

For 75hp Johnsons

How clean is the bottom of hull, outdrive and props (growth)?

What does your spark plugs look like ???? Wet - black - tan or ???

Also prob in needed of spark plugs and possible wires ?.

Compression test numbers are ?

Very Clean flame arrestor and throttle body ?

Fuel injectors needing to be flow tested and clean ???

Well I TOTALLY missed that your 502 in which MERC calls it an 8.2 CATALYST ENGINE. Your engine is a 2010 and up year model -- Not what every else here thinks it is ( the older 502 1993 thru 2000 )..

WOW and WOW --- you took off the catalyst system, manifolds and risers and what did you do to the PCM or NOT do for a correct calibration ???

YOU CAN NOT RUN THE ENGINE ON A STOCK LOCKED calibrated PCM from MERC. when you took off the their exhaust set up and catalyst system. You are going to damage the engine with the stock tune with out those stock OEM parts that were engineered into the calibration from MERC. .

Tech speaking MERC calls this the 8.2 EC engine FYI MERC never brands this engine a 502, why I missed it being a CAT engine to begin with per your calling it a 502.

You are actually down 400 RPM's not 200 rpm's per removing the stock parts for your app.

The 8.2 EC engine is max 5000 rpm's.

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What was your deciding factor on new manifolds, I see your other post. Your STOCK motor was designed,tuned and calibrated to run peak performance with STOCK parts and exhaust. You are only going to gain headaches with only aftermarket bypass systems. Keep it STOCK or rip out everything and start over. You might gain a little with a lighter wallet. I doubt your props are an issue, I've been playing the B3 prop game a while.

Fwiw I have friends who have removed the cats and had no issues. Same as in cars. They are a big pain in the ass. I wasn't there when they were removed and re programmed but to my knowledge the programming was only to handle the O2 sensors and not for tuning purposes. This is a website of people continually modding and improving let's not act like it was perfect from the factory.

No growth. Boat sits on a lift. Plugs are brand new and arrestor is clean. The rest, I don't know.

I replaced the manifolds and collectors with OEM parts. They had 5 years of salt water use on them and one was cracked. So, in the process I decided to ditch the catalyst because I had fouled the post CAT O2 sensors last year and didn't want to deal with the headache anymore. So, I bought a computer that tells the ECM the cats are there.

No more fouled plugs and no more dumping fuel.


Right! The cats are nothing but a PITA and I've already dumped money into replacing the O2 sensors which have a problem of fouling on this motor due to salt spray. The easiest fix is bypassing the post O2 sensors completely and if you are going to do that, you might as well pull the cats.


So, back to my original question and it sounds like I might need to pull the plugs and see how I'm running. We ran WOT last night but I had a full boat load of people and I was around 4600 RPM. Going to go out again today and see if I can get some better numbers. Boat runs great and pulls onto plane very quick. Just trying to figure out why I lost some top end over the last couple years.

Everyone would have to assume when info is missing in posts - never was mentioned about he has the cat eliminator plugged into the system nor mentioned he went back with stock manifolds and risers and the reason why they were replaced from saltwater use. How would anyone know that when the details are not written. Just saying no other intent but if your looking for help you have to write a lot more detailed info in posts to be able to get the correct help.


IMO its the cat eliminator added in the mix as the problem plus it is unproven. I know where he bought from and its hugely discounted. Maybe for reasons unknown - like how well does not it work correctly or needs to start selling.


Most cars that I know DO NOT have a locked tune ECM's from the OEM and have many plug & play different levels of recalls to input.

Also nobody said MERC tune was worth a crap or not either. They really are still way behind on the EFI / ECM side from what a lot of these auto tuners are doing in the auto world.

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It's not the CAT eliminator as the problem existed before any of that work was done.

That being said, I do think I need to send my ECM off to get flashed as I'm getting a ODB Service Soon error on my smart craft gauge which would seem to indicate thee CAT eliminator isn't doing it's job.