MCM 454 to MIE 454 compatibility

[Andreas-Asander]

Hi,

I have a sea ray sundancer 290 - 1996.
Last year my engine, Mercruiser Bravo-II, MCM 454 7.4l gave up and I am now looking at replacing it.

I managed to find a Mercruiser MIE 454 Magnum MPI 7.4l (385 hp) that was recently renovated/serviced at a good price.
However, as I realized that there seem to be some difference between MCM and MIE on the engine I get worried.

As the engine used to sit on an sterndrive and not on a inboard/outbord (alpha/bravo) I am aware that I would need to move the flywheel from my old engine, swap the exhaust knees (pointing forwards now and they need to point backwards facing my bravo exhaust system.
Since there is no power steering pump on the new engine I am also expecting that I need to figure out some way to move the old one to the new one (I am hoping that there are mounting brackets and that I can buy a new belt as I guess its a one-belt system on the Horizon engines.)
As the new engine is an mpi I would also expect to buy new instruments and throttle control.

All that is somewhat manageable, but will the engine fit the boat and allow conversion to work with a bravo-II.

My main worry is that there are too many things different between the MCM and the MIE engines that I wont be able to fit it into my boat.

Anyone who knows these engines well and if it is possible to convert so that it fits a bravo-ii system without to much pain.

Best Regards,
Andreas

 

[Air O'Nautical]

Let back up a bit.....what let go on your current engine?
What the Ser# because, I'd like I know if its a Gen V or Gen VI..

 

[Air O'Nautical]

Doesn't really matter because, any 7.4L will be the same block.
The only difference in the "high output" version is the intake and heads.
The flywheel is the same and you would replace the coupler at this time anyway.
It can work easily if its a same year or newer block and may need minor modifications if its and old Gen IV block. The remote oil lines were different on the old motors.

I'm assuming what your looking at is a late model engine....?

 

[Andreas-Asander]

Doesn't really matter because, any 7.4L will be the same block.
The only difference in the "high output" version is the intake and heads.
The flywheel is the same and you would replace the coupler at this time anyway.
It can work easily if its a same year or newer block and may need minor modifications if its and old Gen IV block. The remote oil lines were different on the old motors.

I'm assuming what your looking at is a late model engine....?

Thanks for the help with this.

Yes, I do suspect that its the same engine block no matter what. Does not make sense to have different engines just to fit I/O or sterndrive.

The "new" engine is a lot newer than my old engine. I think its a 2000 but as its used you can never be sure.
The engine block has the following serial number / cast-number: 10237297

The new engine is a magnum, mpi, horizon and I read something about the oil pan might be different on those. It was something about them being in composite. I would be surprise if they changed the dimension specs that would make it impossible to use as replacement of the older engines.

About the power steering. I guess it must be possible to fit one onto the new engine but is it a matter of a big job?
The new engine seems to have a single belt setup while my old one has multiple belts, whereof one was for the power steering.

What do you mean with remote oil?

BR
Andreas

 

[Air O'Nautical]

Ok, the inboard engine can be converted to to an IO configuration with use of your flywheel housing and buying the necessary brackets to to add the PS pump but.....

Your going to end up with a used (unknown) engine. Why not fix your engine, even if its up to a new longblock and reuse your current components..

What went wrong with your current motor?
A new to you used motor isn't likely the best route to go...

 

[Andreas-Asander]

Ok, the inboard engine can be converted to to an IO configuration with use of your flywheel housing and buying the necessary brackets to to add the PS pump but.....

Your going to end up with a used (unknown) engine. Why not fix your engine, even if its up to a new longblock and reuse your current components..

What went wrong with your current motor?
A new to you used motor isn't likely the best route to go...

Well, I wish I could agree with you on that.
however, as I only owned the boat for 2 years (imported it from the states) and I only had problems with it I am not sure I trust my old more than the new (even with a new block).
The "misc" parts (generator, starter, mercatode, carburator, hoses, thermostat, etc) are all old and to be doubted.

The new engine is newly renowated, sure, might have other problems too. Price thou is what a new block will cost me.

Hard to say what is best...

 

[Air O'Nautical]

I understand the loss of trust thing but, the items you mention are replaceable wear items...except the mercathode has nothing to do with the way an engine runs.
The other thing are easily replaced.

Just trying to save you headaches....to answer you initial question.

Yes, it's very possible to to replace any 7.4L powered boat with another 7.4L engine.
The addition of fuel injection means the newer motor will need its computer to be part of the package because, a carburetor engine won't have one.

 

[Bt Doctur]

You need to use the I/O flywheel and housing.Most of the external items should just bolt up so you can use your ps pump brackets. You may have to revert back to your pully system

 

[Air O'Nautical]

You might also need an electric fuel pump depending on the year of the new motor.

 

[Andreas-Asander]

Thanks for all the input.
In the end I decided to buy a new engine block instead of taking the chances with an old-unknown one.

BR
Andreas