8T8242LS

Trying to install a set of EMI Thunder manifolds on my 1988 242 LS with a silent thunder and am having nothing but problems. I have everything all mocked up and the risers do not line up with the transom exhaust holes. The risers are 28 1/8" center to center and my boat is about 25 1/2 center to center. Eddie marine part number #EMI-552 States that it will fit and is a direct replacement for most alpha and bravo drives, but one of their tech guys just told me that all the riser spacing on their manifolds are 28 1/8" has anybody installed these on there earlier boat with the silent thunder or does anybody know standard alpha/bravo center to center ? I don't want to re-do the exhaust holes in the transom ! Worst part is I am committed already having relocated the control cable plate & remote oil filter and cutting all the hoses for their manifolds ! Some help would sure be a prescient it thanks !!

oconnor marine

I have emi exhaust on small blocks in 88272 sr1. what power do you have?

8T8242LS

Ooops should have said that it's a 7.4 454

Mr Maine

Was your 242 originally a small block boat? Small blocks are narrower. I can measure mine to see what they are later today. You may need to fab up some 4 inch stainless offsets.

8T8242LS

If you could measure Mr Maine that would be cool, nope the boat is original 330hp 7.4 with a bravo 1, was thinking the same thing either flex or soft wall exhaust hose instead of the factory hard wall rubber exhaust hose !!

79formula

I have EMI Thunder exhaust on my 242. I needed them 3 inches taller than stock risers. I had stock height risers and they were too low. here is a few pics.

8T8242LS

FRICK !?!? I don't get it ?? My problem is not the height but to wide, my center to center is 25 1/2" on the transom and the manifolds are wider, wide enough to make the rubber hose not line up . Do you happen to know what your center to center on your transom ? do you have a Silent Thunder ?

Mr Maine

My small block is 24 on center at the transom, the big block is 27.5 on center. Stainless marine on the small and gils on the big. Formula 206 and 311

8T8242LS

Does the Silent Thunder on my boat have something to do with my 25 1/2" center to center ??

Mr Maine

My guess is the split the difference between the spacing of the BBC and the sbc since the boat came with both. I have a friend with a 242 BBC with sm exhaust no issue. I can have him measure his but we have snow coming so may be a couple days