What would be more reliable merc. 525sc or 502mag w/blower set up?
10-08-2014, 11:27 PM
#14
Registered
Eddie
10-09-2014, 08:26 AM
#15
Registered
Thread Starter
Join Date: Apr 2014
Location: Delaware,oh
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
Hey Eddie im just curious on what kind of gains i could get from doing work to my heads, bigger cam, set of rockers, and alum. intake? Just until i do the motor upgrade!
10-09-2014, 11:51 AM
#16
Registered
Are you talking about working with the current 330 hp engine?
The limiting factor with it is the heads. Those are peanut port heads and really aren't worth dropping the money on them. I also wouldn't spend the money on an intake, since it will really only work with those heads. If you bought a rectangle port intake that you could use later, you would have serious port misalignment with the current heads. IMO, that engine isn't worth sinking the money into. Just save your money and start with a better platform.
Eddie
The limiting factor with it is the heads. Those are peanut port heads and really aren't worth dropping the money on them. I also wouldn't spend the money on an intake, since it will really only work with those heads. If you bought a rectangle port intake that you could use later, you would have serious port misalignment with the current heads. IMO, that engine isn't worth sinking the money into. Just save your money and start with a better platform.
Eddie
10-09-2014, 02:09 PM
#17
Registered
Thanks for taking the time to provide info, you are an awesome contributor to the boating world.
2 Quick Q's
1. How much hp would you expect from a 20 hour refreshed 502 mag by simply changing to a great fully assembled head, cam, and thinner gasket? this is a carbureted motor.
2. if a higher than stock hp engine (500-600) is run through the prop exhaust is the hp simply reduced or does it create motor problems?
thank you
2 Quick Q's
1. How much hp would you expect from a 20 hour refreshed 502 mag by simply changing to a great fully assembled head, cam, and thinner gasket? this is a carbureted motor.
2. if a higher than stock hp engine (500-600) is run through the prop exhaust is the hp simply reduced or does it create motor problems?
thank you
If you are running 67-68 mph with 330 hp now, then 500 hp will get you to 80 mph. You need to Eddfigure somewhere around 13-15 hp per mph increase. That only works to a point though.
If you start with a 502 mag, then a few well placed mods will get you to 525 hp very easily. You will need to bump the compression, freshen up the heads to handle the larger camshaft that you will need, change the exhaust,etc. You may want to do a small amount of cleanup work to the heads while they are off. You can just clean up the bowls a little and clean up the chambers where the seats were cut. You can surface the heads and go to a thinner Cometic head gasket to bump the compression without going into the bottom end. If the bottom end needs to be done, then you can surface the block some since the piston is about .020 in the hole. Just by surfacing the heads and using a thinner gasket, you should be able to get close to 9:1. That along with the head work and cam change should get you to 500 hp. Don't forget that the ecm will need programming.
Eddie
edit: Just saw that it's NOT a GPS speedo. I saw GPS but didn't read carefully enough. That sounded pretty fast for that little bit of power but I'm not familiar with that particular boat. Anyway, my speed estimates are based on your current speedo (Dream meter) lol
If you start with a 502 mag, then a few well placed mods will get you to 525 hp very easily. You will need to bump the compression, freshen up the heads to handle the larger camshaft that you will need, change the exhaust,etc. You may want to do a small amount of cleanup work to the heads while they are off. You can just clean up the bowls a little and clean up the chambers where the seats were cut. You can surface the heads and go to a thinner Cometic head gasket to bump the compression without going into the bottom end. If the bottom end needs to be done, then you can surface the block some since the piston is about .020 in the hole. Just by surfacing the heads and using a thinner gasket, you should be able to get close to 9:1. That along with the head work and cam change should get you to 500 hp. Don't forget that the ecm will need programming.
Eddie
edit: Just saw that it's NOT a GPS speedo. I saw GPS but didn't read carefully enough. That sounded pretty fast for that little bit of power but I'm not familiar with that particular boat. Anyway, my speed estimates are based on your current speedo (Dream meter) lol
10-09-2014, 04:21 PM
#18
Registered
Thanks for taking the time to provide info, you are an awesome contributor to the boating world.
2 Quick Q's
1. How much hp would you expect from a 20 hour refreshed 502 mag by simply changing to a great fully assembled head, cam, and thinner gasket? this is a carbureted motor.
2. if a higher than stock hp engine (500-600) is run through the prop exhaust is the hp simply reduced or does it create motor problems?
thank you
2 Quick Q's
1. How much hp would you expect from a 20 hour refreshed 502 mag by simply changing to a great fully assembled head, cam, and thinner gasket? this is a carbureted motor.
2. if a higher than stock hp engine (500-600) is run through the prop exhaust is the hp simply reduced or does it create motor problems?
thank you
2- Power will certianly be reduced, but you could also certainly damage the engine by reversion. Again, it will all depend on the parts you choose. With the above mods, you will need to go to a better, aftermarket exhaust. You can still run a silent choice type setup, but you will be limited on camshaft size. You will need to know that going in when choosing a cam. It will have to be able to work with the silent chioce exhaust. This will also limit your power capabilities.
Eddie
10-09-2014, 07:21 PM
#19
Registered
Thanks for taking the time Eddie
Sounds to me like the best approach is a proven set of aftermarket heads that are complete with a bob madera cam
Sounds to me like the best approach is a proven set of aftermarket heads that are complete with a bob madera cam
1- The exact head, cam choice, how much you raise the compression, etc. will all determine how much power it will make. I would expect to see anywhere from 500-550 hp (maybe more), depending on what choices you make on parts. Are they stock replacement heads or aftermarket (cast iron or aluminum), how big is the cam, etc. All of those things will come into play. The better the head and cam choices are, the more power it will make.
2- Power will certianly be reduced, but you could also certainly damage the engine by reversion. Again, it will all depend on the parts you choose. With the above mods, you will need to go to a better, aftermarket exhaust. You can still run a silent choice type setup, but you will be limited on camshaft size. You will need to know that going in when choosing a cam. It will have to be able to work with the silent chioce exhaust. This will also limit your power capabilities.
Eddie
2- Power will certianly be reduced, but you could also certainly damage the engine by reversion. Again, it will all depend on the parts you choose. With the above mods, you will need to go to a better, aftermarket exhaust. You can still run a silent choice type setup, but you will be limited on camshaft size. You will need to know that going in when choosing a cam. It will have to be able to work with the silent chioce exhaust. This will also limit your power capabilities.
Eddie
