|
More power for my 311/TRS
Not this season but perhaps the next, I'm thinking of doing some engine upgrades to the 311. Currently, she has 1999 502 MPIs with a little under 400 hours on each engine. CMI "cool collar" E-Tops with the water mixing at the transom hose connections. The heads were redone on one of the engines probably 200 hours ago. I'll probably have both redone during my upgrade. She does not burn oil, and the plugs are perfect every time I pull them so I think the short block are good candidates for top-end only work.
I have full Latham steering... a huge upgrade that has made the boat much faster in the rough stuff. My thoughts on upgrades: 1. Remove the MPI set up (some will scoff at this, but I'd rather have the simplicity of carbs, and to make good power, the intake has to go anyway). 2. Freshen up the 088 casting heads, and do some pocket porting (I can do the porting myself). 3. Crane 741 roller with Comp 929 springs. 4. Crane Gold rockers with studs to replace the existing non-adjustable set-up. 5. Edelbrock Performer RPM Air Gap with a Holley 850. 6. I might keep the factory Cool Fuel set up (haven't had any issues with it), and use a regulator to manage proper carb-friendly fuel pressure (will the pump supply enough fuel?). 7. Keep the factory distributor using the limp-home module for a basic curve (timing set at 34 degrees or so). Depending on what the heads look like to upgrade cost-wise, I may look at alternatives some alternatives. Depends on what funds are like really. I'm thinking the above will get me to about 575 HP and 600 lbs ft of torque per engine. The question... with the requisite prop change... will it be enough to make a noticeable difference (say 10 MPH) or am I forever stuck at 69-70? The gain would be more than 150 HP per side. I know the TRS can be a detractor here, but I do not think it would make that much of a difference in the end... and I will not give up the smooth shifting of this set up so they're staying. What do you guys think? Doable? How much faster? |
MY 311 bravo with approx 600 HP blower motors would run low 80s. What exhaust are you planning on running?
|
I will keep the CMI Etops and long TRS tail pipes. I don’t think reversion will be a factor considering how far down the line the water mixes in. I’ve considered blowers, but I didn’t want to have to mess with the hatch. 250 blowers might fit, and the 502s as they sit with 5-6 pounds will make about 600 HP without really going into the engines. I’m tempted to go that way, but I don’t know if they’d fit without some surgery. Can’t beat the torque with blowers that’s for sure! |
The decision process is the hardest part, second to paying for everything. The balance is to get as much power as you can without giving up reliability and longevity. The snow ball just rolls and rolls and the price goes up and up. I think you can meet your goals with blowers and port work and 731 cams that won’t require as short a maintenance interval as 741’s. The little sh!t just eats you up on these upgrades. I know I’m not telling you anything you don’t know. If I could spend your money, I would go with a couple mildly built 572 tall decks. Only kidding. Best of luck Tom. |
Tom,
Make that girl faster...I am a big fan for the blowers idea....or you can go my route and build a set of 509's at 675hp naturally aspirated...let me know if I can help. Chris |
Tom, I have a Formula 303 sr1 that had stock 502 carbed motors. I spent $30k building 540s that made 670 hp and I only picked up 8 mph. These hulls run out of bottom around 80-82 mph.
|
I think I’d be pretty unhappy spending that kind of coin to only gain 8 MPH. I’m not familiar with the 303 though I do believe they are very different than the 311. I’ve never seen a 303 in person, but that’s my understanding. Looking through the forum, it seems that there have been some pretty fast 311s, and that 600 HP seems to be the level needed to really make these old girls fly. Torque is key, and that comes with the blower. I don’t think an NA engine will make the torque needed to really spin the higher pitched props. I gained 20+ mph going to a 250 blower and 525 EFI cam with my 454 in my 242. That engine was making 600 ft lbs at cruise! I think the case is really made to go blown to get this done. |
Originally Posted by TomZ
(Post 4675655)
I think I’d be pretty unhappy spending that kind of coin to only gain 8 MPH. I’m not familiar with the 303 though I do believe they are very different than the 311. I’ve never seen a 303 in person, but that’s my understanding. Looking through the forum, it seems that there have been some pretty fast 311s, and that 600 HP seems to be the level needed to really make these old girls fly. Torque is key, and that comes with the blower. I don’t think an NA engine will make the torque needed to really spin the higher pitched props. I gained 20+ mph going to a 250 blower and 525 EFI cam with my 454 in my 242. That engine was making 600 ft lbs at cruise! I think the case is really made to go blown to get this done. Get it done and make sure you are at the Chesapeake Bay Family and Friends Run weekend of May 3-4 Chris |
We're going to try to make it Chris! I have to do some trailer work, and get the trans swapped out! I'm about a month behind because of weather and the flu. But we most certainly are going to try hard to make it!
The engine project is a next year thing. Last season, lots of rain, the swim platform change-out, and having the boat down for a month to finish the Latham steering project soured me on doing projects outside of general maintenance during the season. I'll start collecting parts throughout the year, and then look to do the refreshes and upgrades starting in November; that's my plan anyway! |
Originally Posted by TomZ
(Post 4675674)
We're going to try to make it Chris! I have to do some trailer work, and get the trans swapped out! I'm about a month behind because of weather and the flu. But we most certainly are going to try hard to make it!
The engine project is a next year thing. Last season, lots of rain, the swim platform change-out, and having the boat down for a month to finish the Latham steering project soured me on doing projects outside of general maintenance during the season. I'll start collecting parts throughout the year, and then look to do the refreshes and upgrades starting in November; that's my plan anyway! If there is anything I can do for you to help please let me know. I will be happy to come down to VA to help...plus it will give me an excuse to come and harass C.H. (AKA-wrench monkey)... that I will get him to help with whatever you need. Chris |
Thanks Chris! That’s a reallly generous offer! I’ll keep you posted. We’re hoping to get the trans out and back in this weekend so long as the weather holds. Then it’s time to work on the trailer. Speaking with Doug at Owen and Sons, we’re thinking it may need an axle or two (tires making contact with the bunks). |
Originally Posted by f311fr1
(Post 4675481)
MY 311 bravo with approx 600 HP blower motors would run low 80s. What exhaust are you planning on running?
|
Bringing this back up...
I have been acquiring some parts over the last couple of months. I have a complete set up for the valvetrain for both engines, Crane 621 cams, Crower rockers, Comp springs, etc. I should have a set of AFR 325s coming in from another OSO member this coming week. I redid the top-end on my port engine prior to this season, and performed compression tests on both engines... 155-160 across the board and the one short block looked great when I had the top-end apart so I'm not going to need to go into the crankcase for a while yet. I'm hoping for 600 or so. I might be a little weak on the cams. As mentioned earlier the 731/621 cams are not as hard on the valvetrain as is the 741, and the AFRs should really flow there asses off no matter what. All I need now are carbs and intakes, and maybe fuel pumps (haven't quite figured out that part just yet). Closed cooling is also something I need to work on considering it's a saltlife world around here. If anyone has some 1000 cfm carbs and single plane manifolds laying around, hit me up! Had some relationship issues pop up that will afford me a whole lotta time for messing with the engines so perfect timing (I guess... that part of my world sucks). Time to make some power! |
The old "Tramp" 311 ran 80 with over cammed 496's and TRS. I'm mid 70's with 454's and 500efi cams. I'm interested to see where you end up with your build. I will need to do top end sometime in the next few seasons anyways, leaning towards putting my heads and valvetrain on some 509's or similar.
|
I picked up the heads last night so we’re going to on our way soon. At this point I have everything needed except for the intakes and carbs. I’m considering using my electronics and staying injected, but instead of direct port, it would be TBI. I’m looking forward to the project. As it begins coming together, I’ll update here as well as on FB. |
Tyler, what heads are on your 454s? |
Originally Posted by TomZ
(Post 4714962)
Tyler, what heads are on your 454s? |
Your mechanical pumps will feed the carbs. You should have mechanicals acting as lift pumps to the FI. |
I have Gen VI’s with Cool Fuel pumps. No mechanical pumps on my set up. |
| All times are GMT -5. The time now is 07:19 PM. |
Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.