F242: How FAST with <insert config here>?
 

I'm always trying to figure out how to go a little faster and what changes will help the most on a 242. There is a lot of great info on this site, but sometimes hard to find, so.... I scraped some 242 speed data from several threads and put it all together (not without some abuse from my wife that I was wasting my time and had a million better things to do).

Yellow in the MPH column means the speed was not specified as GPS. This bitmap is hard to read, so I included a pdf. The source thread is included if you want to read about a specific entry.

The WINNER is..... (for now anyway) a tie:

mikemracing @ 75 MPH
86242ls @ 75 MPH

That's fast for this boat! :boat:

cool you put some time into that:grinser010:

Good work. Out of curiosity...what is your RPM at top speed with your set up and what props are you running? Also...what is yout "sweet spot" cruise speed and RPM?

I think thats a good catagory, that is RPM @ top speed.
On my 242 LS its 64.5 with a Mirage (non-plus) 21 pitch @ 5800 rpms. I've done a few mods as well as a new 21 Mirage Plus this winter so I'll soon see if that helped my speed.

I need mine updated
Lightning Headers, Upgraded cam and intake on my 502 and added a -2" shortie
Best of 73.4 mph

Cool notes!

I've been thinking about adding a shorty on my boat. What kind of gains did you get vs standard lower...

The boat rode much flatter with the shortie, didn't take as much trim to get up to max RPMs. Speed gain was 1-2 mph, but it was consistanly faster. Didn't have the "on a good day it ran 71+, we would run over 71 almost any day. Didn't need the perfect conditions anymore.

Thanks - I think it was around 4700-4800 RPM. I cruise at about 3200 RPM. Isn't optimal cruise about 75% of WOT? That should be ~3600 for me.

I hope to post all new numbers this summer. I'm in the middle of replacing the stock intakes and 2 barrel carbs with Edelbrock Performer intakes and Edelbrock 1409 4-barrel carbs (600 CFM). Trying to get to 60 MPH!

Suggest you consider the Holley 4150 600 CFM Marine "Double Pumpers" as replacement carbs....you totally control the secondary opening and throttle response is instant.

I might be a little faster this year I will find out tomorrow, taking it out for a shake down!!!!!!!! trying out a few different props

Agreed!!!

Well....

1) I have the brand new 1409s sitting in my garage (I could return them, but a hassle
2) The Holley 4150s are $110 more, each - and I'd need 2.
3) From what I read about the two carbs, the 1409 is for a beginner - like me - easy and doesn't require a lot of tweaking (and the knowledge to get it right). The 4150 sounds like a great carb for an experienced gear head who knows how to get the most out of it.

Should I REALLY return the 1409s and get the 4150s??? :confused:

IM trying to gain some more speed on my 242ls 1985 with stock 350. I hit 43 Last summer, Dont remember the prop. Doing thru hull this spring. Any suggestions on a quick way to gain speed. (and yes i got a skinnier girl this year :grinser010: )

cubic inches (454)

Considering ALL of the above...no ...keep what you have. Be advised however...the 4150's have worked for me and my brother on 350 MerCruisers "staight out of the box" with no tweaking (other than checking the float level which was fine) required. What I like about the mechanical secondaries vs. vacuum in a boat is that you can hear and feel the secondaries open and close. We get on a plane quickly and back off to a cruise running on primaries only...it's like having 2: 2 bbl carbs on each engine!! With gas on the water at near$4/gal...knowing your running on the primaries only in a cruise can save some $$$.

I have Q-Jets on mine and I just re-built the starboard carb....I understand about economising...but when I do change carbs I'll go to the "Double Pumpers".:evilb: In my opinion the only system that tops it is the MPI.

Make sure that what you have is tuned properly...good ignition,proper timing, clean carbs, fresh plugs, clean fuel filters, straight props. Sometimes that combo can gain 3~5 MPH.

Thanks - you don't think I'll be able to hear the secondaries kick in with the 1409s? I thought they would behave and sound similar - just auto vs manual setting. I agree that hearing it will be important to know I'm not wasting fuel cruising...

Maybe...but you can't really control it as well since the secondary operation is a function of vacuum. With mechanical secondaries there is no question about what's going on....but again in your case since you already have the carbs...run them. You will get a feel for what's going on and can adjust your throttle setting once you know what the sweet spot is.

On my 255 w/ twin 260's with Q-Jets I think my secondaries are starting to open at about 3500~3800 RPM once I'm on plane with an average load. I can run about 40 MPH +/- before they begin to open but I'm really guessing. When i come out of the hole, I trim the drives all the way in...tabs all the way in and gradually push the throttles all the way open. The 255 planes reasonably quickly ....I trim the planes to neutral and leave the drives alone unless I'm planning on a 50 + MPH run. I back off the throttles enough to hold about 30~35 and just cruise on the primaries. My secondaries are all the way in as I'm getting up but they open slowly...they have to because there is no secondary accelerator pump for the back half of the carb...so the secondaries are always waiting for a vacuum signal before they will start opening.

My brother has a single 260 in a Formula F3. He changed from the Q-Jet to the "Double Pumper" last year. His boat jumps out of the hole and has a very crisp feel to the throttle compared to the Q-Jet. Once he learned how to stay out of the secondaries his fuel economy increased about 15% and he added about 5 MPH on the top with no other changes.

Sprink58 - great details. I felt like I was out on the water with you! I'm going the try the 1409s this summer and see how it goes. I like the option of selling them as "1 season old" and getting the "double pumpers" next year. An easy change too.

Thanks.

Time for an update. I replaced the stainless manifolds with Keith Eickert Headers and dumped the old beat up 21 Mirage from last year with a new 21 Mirage Plus. New Speed.... 69 MPH (Livorsi GPS Speedo) @ 5900 RPMs. Last year in flat water I could get 61-62 so thats an increase of 7 MPH. I'll update again once I have Brett at BBlades work the prop.

Damn.....that's strong!!:evilb:

you might want to add from the Factory test of a 1990 242 SS with 502 mag 390 HP and Mirage 23
61.4 at 4900 rpm

I would guess you need a 24P bravo four blade prop.

that's the prop bblades sent me to try I picked up in cruising speed but gained nothing in the top end as of now. The motor spun a main bearing during trial. Hopefully ill have it back together in a few weeks and will get better results.

have you tried a 23 mirage plus? worked good for me might put you into the mid 70'S...

The 23 was a bit slower. This engine was built to rev so I'm right in the sweet spot with this engine.

selling my 242
 

Hi everyone just wanted to let everyone know I'm looking at upgrading so I am looking to sell my 242. Pm me and ill send pictures and info. Thanks Mike

You forgot to mention your's is tied for fastest 242 on this list :-)

Nice looking 242. Good luck with the sale.

Well you can take me off the tied part as well!!! When I swapped over to bravo one the boat loss 8 mph!!! and now rides ass heavy!! but hey its reliable now. Might be going up for sale soon anyone interested?