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311 Engine Upgrades

Old 09-16-2020, 08:44 PM
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Originally Posted by TomZ View Post
Looking at the paperwork (from memory) I believe the tailpipes were custom made for the boat. I can take pics and measurements if that would be helpful.
awesome maybe in the future but not needed right now still in the early stages. Thanks though very much appreciated
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Old 10-08-2020, 09:23 AM
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Some updates...

I'm sure some of you saw the piston fiasco over in the Tech section. The piston ring stuck to the bore and broke the ring land and ring. Half of the ring was gone. Ouch! I broke everything down and now the block is at the machine shop getting cleaned up and bored. So far, no cracks and pressure checks are good so we're moving forward. The crank was also fine needing only a polish. We're boring the block to 4.5 inches and taking about .006-.007 off the deck which; that should give me close to a zero deck. So now I need to decide on pistons and rods. Compression is going to come in around 9.5:1 and with my heads should still allow me to run on 87. I have 500 EFI cams (169621) to go with my AFR 325s. It's been suggested that I bump the cam up to at least a 741 (168741) but I'm not really looking to spin it hard. The heads also make milder cams bigger so hoping I can go this way. The duration split, though a little milder, fits the profile of the head better. I may step up to a 1.8 rocker on the intake to really get after it. Open to suggestions.

Once I have the number one block back from the machine shop, I'm sending number two off to have some of the same treatment. I'm hoping I won't need a bore on that one. I will more than likely replace the pistons since I'll be doing the rods in that one too. The rings are just too expensive and I'd rather not have to worry about blow-by, etc.

Headers. Pressure check using air, water, and heat. I'm happy to say there were no leaks. And to combat any potential issues down the road, I plan to install dumps at the transom that will drain the headers after shut-down.

It's starting to come together.

Last edited by TomZ; 10-08-2020 at 02:34 PM.
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Old 10-08-2020, 09:45 AM
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Originally Posted by SB View Post
www.adblockplus.org free version on your phones and pcís works great.
Worked like a charm!
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Old 10-08-2020, 02:40 PM
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And while my Formula waits on new powerplants, my buddy's Cig Bullet will be over here getting finished up from its engine builds. Taking over the final rigging and finish work from another friend, and I'm hoping we can get some good steering installed while it's here. We'll be running about 1300 HP so it's time to make it safe, too.

I'm sure the neighbors are going to love having two offshore boats at my house!
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Old 10-08-2020, 05:03 PM
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Originally Posted by TomZ View Post
Some updates...

Headers. Pressure check using air, water, and heat. I'm happy to say there were no leaks. And to combat any potential issues down the road, I plan to install dumps at the transom that will drain the headers after shut-down.

It's starting to come together.

good to hear itís starting to come together. Curious how you plan on doing the dumps/drains? This sounds like a good idea and would like more info on it. Any thoughts get or still trying to figure it all out?
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Old 10-08-2020, 05:20 PM
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Originally Posted by Smoke eater View Post
good to hear itís starting to come together. Curious how you plan on doing the dumps/drains? This sounds like a good idea and would like more info on it. Any thoughts get or still trying to figure it all out?
Thanks!

I have it figured out for the most part. Itís been done by a few guys here on OSO so Iím just using what Iíve read/learned.

Basically, Iíll add fittings at the back of my distribution tubes, and then theyíll go out to fittings on the transom. The fitting from the tubes will neck down to a -4 AN fitting and hose then connecting to a corresponding fitting on the transom. No ball valves are involved because water flow and pressure will follow the path of least resistance while running. When you shut-down, they drain.



Last edited by TomZ; 10-08-2020 at 07:23 PM.
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Old 10-09-2020, 08:16 AM
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Tom I really like our 500efi cams. I agree with your statement that the good cylinder heads make them seem bigger. Easy to get them to idle solid for shifting gears and still run up well into the upper 5k range. Really need to take a look at how you boat.. idle time... cruising speed.. etc. Those 741's are gonna make quite a bit more power in a lot of areas but there is always a compromise.
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Old 10-09-2020, 10:20 AM
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Originally Posted by TylerBurich View Post
Tom I really like our 500efi cams. I agree with your statement that the good cylinder heads make them seem bigger. Easy to get them to idle solid for shifting gears and still run up well into the upper 5k range. Really need to take a look at how you boat.. idle time... cruising speed.. etc. Those 741's are gonna make quite a bit more power in a lot of areas but there is always a compromise.
Thanks Tyler. The boat is never going to be the fastest out there. Hull mods, drive changes, etc; I'm not keen on doing anything like that. I'd look at getting a different boat if I wanted something like that. Building a strong cruise with the ability to turn 55-60 at a lower RPM with the ability to approach upper 70's to 80 here and there is what I'd really like. I think that helps point me in the right direction.

Last edited by TomZ; 10-09-2020 at 10:29 AM. Reason: clarification
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Old 10-09-2020, 10:46 AM
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Originally Posted by TomZ View Post
Some updates...

I'm sure some of you saw the piston fiasco over in the Tech section. The piston ring stuck to the bore and broke the ring land and ring. Half of the ring was gone. Ouch! I broke everything down and now the block is at the machine shop getting cleaned up and bored. So far, no cracks and pressure checks are good so we're moving forward. The crank was also fine needing only a polish. We're boring the block to 4.5 inches and taking about .006-.007 off the deck which; that should give me close to a zero deck. So now I need to decide on pistons and rods. Compression is going to come in around 9.5:1 and with my heads should still allow me to run on 87. I have 500 EFI cams (169621) to go with my AFR 325s. It's been suggested that I bump the cam up to at least a 741 (168741) but I'm not really looking to spin it hard. The heads also make milder cams bigger so hoping I can go this way. The duration split, though a little milder, fits the profile of the head better. I may step up to a 1.8 rocker on the intake to really get after it. Open to suggestions.

Once I have the number one block back from the machine shop, I'm sending number two off to have some of the same treatment. I'm hoping I won't need a bore on that one. I will more than likely replace the pistons since I'll be doing the rods in that one too. The rings are just too expensive and I'd rather not have to worry about blow-by, etc.

Headers. Pressure check using air, water, and heat. I'm happy to say there were no leaks. And to combat any potential issues down the road, I plan to install dumps at the transom that will drain the headers after shut-down.

It's starting to come together.
9.5:1 is really pushing it with 87 octane without knock sensors and efi
you need to pick pistons before youíll know what the deck height will be, and final compression ratio
dont drain youíre headers until they have cooled down. The water will pull the heat out long after shut down and insulate the outer tube. Dump the water once after running and see how hot the tubes get while sitting. That heat cycling is way worse for the headers. Draining them when shutting off should only be done if you realize you have a leak and donít want the water draining into a cylinder.
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Old 10-09-2020, 11:34 AM
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Not seeing 169621 in the catalog. Do you mean 721? 500efi was a 731 I thought.
721 214/220 .553/.564
731 226-236 .587/.610
741 236-244 .610/.632

731->741 was worth 25hp or 5% at least for Merc. A 721 would give up a lot.

Are your heads full CNC chamber? Getting some duration over .600Ē lift would appear to be worth a lot of power. Probably 30hp at least going from .550-.600 on its own.




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