New engine in my 242SS
 

Hi Guys

Considering buying this engine see pics ...
Will this fit under my hatch on my 1988 242 SS??

Looks kind of high to me, hope not....

Rebuild Merc 500 hp, 540 hp now 15 hours after rebuild

On my existing 454 330 hp I have a 3 inch spacer on my riser.
is that standard with 242SS with silentthunder platform?

I would maybe need to modify the Hardin headers on the "new engine" ??

What prop should I use ?

What kind of top speed?

Well, no one can really tell for sure unless they take a tape measure and check the distance from the bottom of the engine mount to the top of the flame arrestor.
If your current engine is still in the boat, then you could check the clearance as well and compare with the 'new' engine.

My 242SS does not have the 3" risers . . .

the tough part of the clearance is in the first 15-18" of the engine compartment were the bench seat portion of the engine hatch is lower. . . . after that, it is similar clearance to the 242LS.

So, my advice would be to grab the tape measure.

My old 1989 242ss with a 330B1 did not have the 3" risers (silent thunder also)

Thank you for the reply :-)

I have rebuild the transom complete rotted out :-( So every thing is out of the boat at the moment, engine and engine hatch. So I do not have the posibilty to measure at the moment.

Pics of rotten wood and newly rebuilt transom

If anyone could measure the hight from the engine mount to the point where the flame arrestor hits the engine hatch it would be great. As shown on the pictures this is the higest
point on this engine.

Next question why does my engine have the 3" riser.

The engine is not original, boat 1988 engine Merc454 GenV 1996. Could it be that the former owner bought an used engine which by accidentaly had a 3" spacer and installed it as is?? I have no Idea... ? It seems like some boats have it and others not????

Experts please tune in, do I need a 3 inch riser of any reason in a 242SS 1987 - 1992?? (With Silent Thunder platform)

Could it be a danger for reversing wather into the engine without the 3" risers??

Thanks
Rune

Thanks for the reply :-)

Another one without 3" spacer....

Picture of my engine before taken out of the boat

Please guys anyone who can give some inputs or facts here ?

:-)

ill be working on my 89 242 ss tomorrow...

I will check my risers and measure the distance from the engine mount to the top of the flame arrestor (i have no idea how I would measure from engine mount to top of the hatch?)

Just get right in the engine compartment with a tape and flashlight and have someone you trust lower the hatch!!!!

Well now the engine is installed

Looks nice, still a litle worried regarding the angle
of the the risers :-/

No problem with the hatch and top of the carb

The challenge I have, is that the engine do not get enugh
fuel. Could it be the the fule hos from the tank to the
fuel filter is not the correct dimension for this engine??

Did not have this problem with my 454......
the new engine has aprox 540 hp, any tip regarding
propeller?

Try removing the check valve that is on the tank. I had to remove mine as it was a restriction! Let us know what you get for speed. My LS with similar power was around 68 MPH.

Tanks for the reply, i will start with that tip

What kind of prop did u use ?

Did you have tall pipes, as mentioned before my old 454 had a 3 inch
Spacer. I am worriied "about reversing"

Br
Rune

New installation looks damn nice Monaco! :whistle:

What rpm range are you looking for? My friend spins a 3 blade 25 on the same boat with a 500hp, right at 5000 rpm. My guess would be to start there or a 24 4 blade bravo prop.

Thanks :-)

I am more of less happy, but we did everything in a kind of hurry, to get something out of the summer.

I will tidy up some of the wiring.
I rember your instalation of the 496 HO in your 242 LS
that was something else, almost perfect

Best regards
Rune

Thanks for the reply

I was thinking the rpm range should be 5000 - 5200 so
mirage 25 plus could be a start

Do you know what kind of speed does your friend do?

BR
Rune

66-68 mph 3blade mirage 25 pitch

Did your 242 LS 496 HO make 56 knots aprox 65 mph gps ??

Thats not bad, must have been å god combination :-)

My engine was a high revving 439 with around 525 hp. My best prop was a Mirage Plus 21 pitch at 5900 rpms. I was typically at 68 MPH.

On a good day I saw 64-65 mph with the 496HO and superlabbed 28p with 1.65 drive ratio.
I saw 62-63 everyday.
But the 4 blade definitely gives some advantages in acceleration and hole shot!

I think you should start with a Bravo I 24p 4-blade. If that is to small go for a labbed 26p..
Testing props is fun!

Happy New Year all

Any one have exhaust system with tall pipes in their Formula 242 SS ?

BR

Rune

Hardin Marine cyclone exhaust
 

I wouldl like to change to tall pipes, to prevent reversation.

I wonder if it is space enough under the hatch ???

( my boat is indoor for winter, no access to measure before spring)

The total height is 17-1/16, 2-1/4 inches higher then my stock merc 454 with 3 inch spacer ???

I am ready to order just need to know if I have room enough

Please give me input 😀

Winter greetings from Norway

After re-reading your post, you are keeping the silent thunder platform you should be fine. I looked at post 9 with a pic it looks like all is good. Remember the platform blocks the water from going right to your pipes and your exhaust going into the platform sits a little higher in the platform. Or are you just looking for a more free flowing exhaust.

I hope some of this makes sense

mark

Hi Mark

Thank you for the reply 😀

The only reason for the change to tall pipes,are to avoid any reversation. The pipes that I have now is for silent choice, which I do not have.

My ST platform has to wholes under each chamber, water flow in and out. Out when engine is running. If I have understood the ST function correct are ther constant water in the chambers until you more or less
Reach planning speed, or? Also if I have understand the critical point of water reversation is when you turn of the engine or also possible when idle? I would be more then glad if the ST Platform also have the function
To prevent potential reversation, as I under stud was a issue with the Merc 500 blue racing engine. I would be pleased to save the money 😀

What du you think Mark?

I don`t know a lot about those engines but better to be safe than sorry. I know your ss will be one of the fastest out there,I`ll be following your progress.

Reversion is the process by which water enters the cylinders. Typically, this happens because the cam in the engine has a large overlap which allows the pull of "air" back to the cylinder. If your risers are too short to where the water mixes with the exhaust gasses this vacuum will pull water in. You can ask around on here to find out if the cam you have will do so. If you are using the manifolds that come on that motor you shouldnt have a problem. Reversion typically isnt caused by water coming in from the back of the boat. I am unaware that anyone has had trouble with it. Not saying it isnt possible, just, I havent heard of it. If you go with exhaust tips make sure they have internal flappers and you shouldnt have any issues at all. I hope this helps. BTW currently have my 88 242 SS under the knife. Rebuilding 454 to 496 all eagle or scat forged internals with dart heads. Currently working on transom issues.