omc change over

mayjean123

Seaman Apprentice
Joined
Sep 5, 2004
Messages
41
just a question I have a 1980 28 foot pontoon with a omc 120 4 cly stringer 400 out drive I am putting a mercruiser out of a boat with a 165 6 cly should I change the gears over to the 120 4 cly merc motor or leave them the 165 6 cly motor
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Don't blame you for changing over to Merc. but have to agree this is going to be quite a project. Have you compared the OMC and Merc. transom cutouts and motor mounts?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,306
pull the entire OMC package from controls to prop and sell what you can

rebuild the transom to reduce the cutout from the size of a buick to the size of a lunch box (use the money from the sale of the OMC stuff to help with this)

install complete Mercruiser package from controls to prop
 

mayjean123

Seaman Apprentice
Joined
Sep 5, 2004
Messages
41
I have the whole set-up out of a Larson 18 with a 6 cly 165 merc steering wheel to prop even cut out the transom for a template your right on big job but worth it have omc parts for sale
 

lmuss53

Lieutenant Junior Grade
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Sep 9, 2008
Messages
1,227
I'm not sure how it would apply in a pontoon transom, but I've heard of keyhole conversion kits to modify the OMC transom to fit the Mercruiser drive.
 

1983 ercoa 21'

Chief Petty Officer
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Jan 12, 2014
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632
When your doing the transom raises the mounting of the outdrive 2-3 inches for less drag and better efficiency.
 

mayjean123

Seaman Apprentice
Joined
Sep 5, 2004
Messages
41
the transom is three pieces of 3/4 marine plywood so that is the easy part just have to cut new hole in a new set-up and relocate engine I saw something about keeping the cavitation plate even with the bottom off the engine pod thanks for all the help
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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