8.1 Upgrades before install
10-15-2013, 10:15 AM
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8.1 Upgrades before install
I know this isn't a truck but maybe you guys have some ideas....
I have a 98 Maxum 3000SCR that has a pair of Wayyyyyyyyyy underpowered 4.3's in it with Bravo II's. I know this is not a offshore speed boat BUT I picked up a boat that was damaged in Sandy with a almost new pair of the 375hp 8.1 motors in it and Bravo III drives, Boat never took on water but did get some damage and I got it for about the price of a Bravo III drive. I don't know the hours of my 190hp 4.3's but the owner I bought it from used it every weekend so I imagine they are a bit tired, I can't plane out unless its just me and the wife, bring a few friends on with some luggage and coolers and it will never happen. Ideally I would want some nice 6.2's or something but getting some FWC Fuel Injected engines with drives for the price I did I can deal with it being a bit cramped in there. Anyway I am gonna start the removal process of the 8.1's hopefully this weekend. My boat is still in the water and I will keep it in as long as the weather will allow me. I'm sure the 375hp motors would be fine in my boat as one motor is about the total HP of both of my current motors. Don't reply telling me the transom/stringers won't take the power as that will be my live and learn as this is happening. I do not go WOT much, I just want to be able to have a much broader cruise range. I have a Garmin 740S with fuel sensors and all the stuff to find my ideal cruise spots.
So after a ton of reading on this forum and a few others I come to realize the only difference between the 375hp and the 425hp is the cams, PCM and about a 5/16" hole in the TB. Well turns out the Marina I bought this boat from has another boat with some damaged HO motors in and told me for a case of beer and the regular PCM's I can swap them and get the HO PCM's! I would imagine the fuel curve/timing curve would be a bit off so I would need to swap the cams also. I am not against swapping cams but I really don't want to spend all the extra money on valve springs and so on for some of the larger cam upgrades - If that is my best bet then it is what it is and I will but I can't afford a computer reprogram and such also after all of that. Anyway I can not seem to find any 425HP factory cams for sale used, been looking for about a month or so. That brings me to the aftermarket, I seem to trust Raylar but at almost $500 per cam it kinda makes it harder when you need 2, I think the only other company is comp and the biggest cam that they seem to have is:
46-422-9
Basic Operating RPM Range: 1,200-5,200
Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 224
Duration at 050 inch Lift: 218 int./224 exh.
Advertised Intake Duration: 270
Advertised Exhaust Duration: 276
Advertised Duration: 270 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Valve Lift with Factory Rocker Arm Ratio: 0.510 int./0.510 exh.
Lobe Separation (degrees): 114
According to a post from RMBUILDER the factory specs are:
The standard marine 8100 cam is:
204º/209º @ .050”
.282”/.284” Lobe
.480”/.483” Valve
118º
The HO cam:
224º/233º @ .050” (222º/232º)
.300”/.300” Lobe
.510”/.510” Valve
114º/115.5º
Not being much of a cam guy it seems the comp is still slightly smaller then the 425HP cam, Is this worth the upgrade or should I keep the search on? Should I just bite the bullet and buy a Raylar cam and do the valve springs and such, Comp cam is just under $300 each where the Raylar is 489 each OR $1249 each with the spring kits and roller rockers and such. Anyway while the motors are out it kinda seems like common sense that if I could gain a total of 150HP extra HP with just needing a pair of new cam's it almost seems too good to be true.
Speaking of the Ralyar Roller rockers, they look just like the PRW's that I can get for around $250ish for a BBC, has anyone looked into these or other options to fit under stock valve covers?
I have a 98 Maxum 3000SCR that has a pair of Wayyyyyyyyyy underpowered 4.3's in it with Bravo II's. I know this is not a offshore speed boat BUT I picked up a boat that was damaged in Sandy with a almost new pair of the 375hp 8.1 motors in it and Bravo III drives, Boat never took on water but did get some damage and I got it for about the price of a Bravo III drive. I don't know the hours of my 190hp 4.3's but the owner I bought it from used it every weekend so I imagine they are a bit tired, I can't plane out unless its just me and the wife, bring a few friends on with some luggage and coolers and it will never happen. Ideally I would want some nice 6.2's or something but getting some FWC Fuel Injected engines with drives for the price I did I can deal with it being a bit cramped in there. Anyway I am gonna start the removal process of the 8.1's hopefully this weekend. My boat is still in the water and I will keep it in as long as the weather will allow me. I'm sure the 375hp motors would be fine in my boat as one motor is about the total HP of both of my current motors. Don't reply telling me the transom/stringers won't take the power as that will be my live and learn as this is happening. I do not go WOT much, I just want to be able to have a much broader cruise range. I have a Garmin 740S with fuel sensors and all the stuff to find my ideal cruise spots.
So after a ton of reading on this forum and a few others I come to realize the only difference between the 375hp and the 425hp is the cams, PCM and about a 5/16" hole in the TB. Well turns out the Marina I bought this boat from has another boat with some damaged HO motors in and told me for a case of beer and the regular PCM's I can swap them and get the HO PCM's! I would imagine the fuel curve/timing curve would be a bit off so I would need to swap the cams also. I am not against swapping cams but I really don't want to spend all the extra money on valve springs and so on for some of the larger cam upgrades - If that is my best bet then it is what it is and I will but I can't afford a computer reprogram and such also after all of that. Anyway I can not seem to find any 425HP factory cams for sale used, been looking for about a month or so. That brings me to the aftermarket, I seem to trust Raylar but at almost $500 per cam it kinda makes it harder when you need 2, I think the only other company is comp and the biggest cam that they seem to have is:
46-422-9
Basic Operating RPM Range: 1,200-5,200
Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 224
Duration at 050 inch Lift: 218 int./224 exh.
Advertised Intake Duration: 270
Advertised Exhaust Duration: 276
Advertised Duration: 270 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Valve Lift with Factory Rocker Arm Ratio: 0.510 int./0.510 exh.
Lobe Separation (degrees): 114
According to a post from RMBUILDER the factory specs are:
The standard marine 8100 cam is:
204º/209º @ .050”
.282”/.284” Lobe
.480”/.483” Valve
118º
The HO cam:
224º/233º @ .050” (222º/232º)
.300”/.300” Lobe
.510”/.510” Valve
114º/115.5º
Not being much of a cam guy it seems the comp is still slightly smaller then the 425HP cam, Is this worth the upgrade or should I keep the search on? Should I just bite the bullet and buy a Raylar cam and do the valve springs and such, Comp cam is just under $300 each where the Raylar is 489 each OR $1249 each with the spring kits and roller rockers and such. Anyway while the motors are out it kinda seems like common sense that if I could gain a total of 150HP extra HP with just needing a pair of new cam's it almost seems too good to be true.
Speaking of the Ralyar Roller rockers, they look just like the PRW's that I can get for around $250ish for a BBC, has anyone looked into these or other options to fit under stock valve covers?
10-16-2013, 01:15 PM
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On The Tree
Join Date: Oct 2013
Location: San Diego
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Hi Ocean State,
You are correct, the only difference between the two motors is a camshaft change and programming. The comp cams are smaller in duration than the HO cam. If you're looking for more power than the HO cam provides, our 203 camshaft is as big as you can go before replacing the factory pistons for added valve clearance. You will need to replace the valve springs if you are planning to do a camshaft change.
Roller rockers are not a mandatory upgrade but do free up an additional 18 horsepower on the 496 engine. The roller rockers we use come with a few additional parts specially made for the 496 heads which other suppliers do not offer. Our AFN nuts allow you to use the stock studs without having to put in hours with a local machine shop to fit poly locks to the studs.
You are correct, the only difference between the two motors is a camshaft change and programming. The comp cams are smaller in duration than the HO cam. If you're looking for more power than the HO cam provides, our 203 camshaft is as big as you can go before replacing the factory pistons for added valve clearance. You will need to replace the valve springs if you are planning to do a camshaft change.
Roller rockers are not a mandatory upgrade but do free up an additional 18 horsepower on the 496 engine. The roller rockers we use come with a few additional parts specially made for the 496 heads which other suppliers do not offer. Our AFN nuts allow you to use the stock studs without having to put in hours with a local machine shop to fit poly locks to the studs.
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