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1989 FourWinns - Change out OMC 5.7L (Ford 351) w/ OMC drive to Marine Chevy 350 w/MercCruse drive

Randye

New member
I am considering changing out my existing OMC (Ford) 5.7L engine and OMC stern drive to a Marine Chevy 350 and MercCruise stern drive. I am getting Chevy engine and drive right out of another boat with all linkages and mounts. Does anybody have any experience doing this, and any advice to share? Thank you. RandyE
 
The basic exchange should be straight forward.

Items to look at would be transom assembly hole (cut out), take a large piece of card board and tace it out of the merc boat, measure hieght from bottom also. check to see if the hole needs to enlarged in the omc transom.

The motor mounts may not be in the same location so check that (stringer location). ford vs chevy

Bolt holes thru transom for mounting. the bolt pattern may be slightly different, check that also.

The merc short shift cable is different and will need propper adjustment before use, repost when at that step and we can assist. Also the routing is specific and if not routed correctly can cause rubbing on the coupler or kinks. Be very careful when handling the short shift cable or you WILL be replacing it......

Alignment ( gimbal bearing to coupler) MUST BE DONE before out drive is attached!!!!!!!!!!!!

Make sure you get all the wiring from the guages back including the controll box, trim pump.

The chevy is a 5.7 350, the ford is either a 5.0 (302) or a 5.? (351) The firing order is different so make sure you understand the suttle differences. Also the merc should have electronic ignition, the Omc would have points.

While you are at it, replace the impeller in the merc outdrive...

Use good outdrive oil..merc hi performance is my recommendation. The drive holds ~ 36 oz, follow proceedures to be sure.

That is all I can think of for now......
 
cutout is exactly the same. From the donor boat you need inner transom plate.

I strongly suggest that both boats be side by side till you are done with the project.
 
Thank you chiefalen and kghost. This is good information and I will make sure I follow all suggestions. If you think of anything else, please post. The one thing I got to thinking about is that this Chevy engine is coming out of a larger boat that has two engines. The throttle and gear lever will most likely be a deck mounted lever, where my FourWinns has a side mounted lever with the push pull action. Hopefully I will be able to adapt the existing cables to work with my lever. I would love to replace my existing lever but have not been able top find one anywhere.
 
OMC and Merc controlls are not compatable........They can be made to work but require a lot of remanufacturing........Ask me how I know this..........been there done that......you dont want to!!!!


Look at a salvage place or craigslist or buy new/used somewhere but get a merc!!!

A side mount and a deck mount are the same control box just the handel and mounting is different. You will also need merc specific cables, what manufacturer is up to you but I would suggest NEW, Make sure you get them a bit longer than measured, say 6 -12 inches if possible. Makes routing much easier. NO hard bends, real nice long arcs so no stress on the cables at the control and the back of the boat.
 
If the donor boat had a counter rotating drive, I would suggest you get the standard rotation drive from the donor for your single engine application.
 
donor boat don't have a control and cables?

Drive if single won't matter what way it turns.

And i still say latter for the cables and the control. Only thing you got to worry about now is the lower cable.
 
If the donor boat had a counter rotating drive, I would suggest you get the standard rotation drive from the donor for your single engine application.
Agree!
Also, in some twin engine applications, the drive ratio may vary slightly from that of the same engine in a single engine/drive installation. Not sure about the Merc A drive......, but may be worth asking.

Drive if single won't matter what way it turns.
That is correct!
However, Randy may want to consider replacement availabililty. I also believe that the Mercruiser counter rotation drive is a tad bit more expensive than the standard rotation drive.

I did a quick search: (surprisingly, not much more with the Merc!)
STANDARD ROTATION
The SE106 Alpha One gen. one 1.47, 1.62 or 1.81:1 ratio - is $1,495.
New from Mercruiser all ratios is $3,300 .

COUNTER ROTATION
The SE106 Alpha One gen. one 1.47, 1.62 or 1.81:1 ratio - is $1,495.
New from Mercruiser all ratios is $3,600 .

.
 
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