New transom assembly different?

Hey Mercruiser gurus,
I just finished rebuilding a gen V mercruiser 454 Bravo motor. I bought an entirely new transom assembly. However, now that the motor is setting in the engine bay, the coupler on the engine is higher than the spline. I think all I need to do is shim up the front engine mounts, but before I do, I find it odd that this transom assembly is supposed to be a direct fit, and I did not adjust the motor mounts so it should not be this far off (the testing tool does not even begin to slide into the coupler, it is about half of the circumference too low). Going back to the records of when I bought this, the transom assembly is supposed to be a Magnum, but I was told the only differnce was reinforcement to make it stronger for more hp. I note that there are rubber pads on the rear enginge mount brackets on the transom plate, which would definitely raise the rear of the motor up, but I do not know if there are other differences that would make this install problematic. My questions are:

1) Is the magnum assembly really a direct replacement for the standard bravo assembly? Are there other differences between them?

2) Do I need to remove the rubber pads?

3) Do I need to remove the coil washer and/or the wafer washer to make this thing fit.

A thousand thank yous in advance, because this is keeping me from finishing this rebuild and getting my boat in the water, and my whole family is dying to get on the water because of the quarantining.

Transom housing should not matter . You should check the bottom of the rear mounts . If smooth you need the double wound washer, if knurled you dont but may need the thin washer.
The rubber pads no not raise the engine , the rear mount sits on the doublewound or the thin washer
Some builders use 1/2 inch plastic pads on the stringer could you have lost them?

Bt Doctur said:

Transom housing should not matter . You should check the bottom of the rear mounts . If smooth you need the double wound washer, if knurled you dont but may need the thin washer.
The rubber pads no not raise the engine , the rear mount sits on the doublewound or the thin washer
Some builders use 1/2 inch plastic pads on the stringer could you have lost them?

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The rear mounts on the motor are the same as before, and used both the double wound and the fiber washer. I don't remember there being plastic pads on the stringers (its been months since I originally took the motor out). What they tell me at Mercruiser is that I need to get rid of the fiber washer because of the rubber pad, or use the same set up and pull the rubber off. I think there may well have been spacers on the stringers to lift the front of the motor to the right height, because that is the only thing that would make sense at this point. If I cannot track them down, I will make something to fit there.

Wide a** wake said:

The rear mounts on the motor are the same as before, and used both the double wound and the fiber washer. I don't remember there being plastic pads on the stringers (its been months since I originally took the motor out). What they tell me at Mercruiser is that I need to get rid of the fiber washer because of the rubber pad, or use the same set up and pull the rubber off. I think there may well have been spacers on the stringers to lift the front of the motor to the right height, because that is the only thing that would make sense at this point. If I cannot track them down, I will make something to fit there.

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Ok, I am sure there were no 1/2 inch pads. After messing around with this all day today, I think I see where the problem is. I put the motor back in, and took the double wound washers out. The spline was closer to inserting in the coupler, but still a long ways off. I took the old transom plate, and measured the thickness of the "ears" where the bell housing mounts sit. The new one was 1 or 2mm different, but that should not throw me off as far as I am. Then I noticed that the inner transom plate is slotted, and therefore adjustable up and down to some extent. So, tomorrow I will take the motor out (again) and move the plate down to lower the back of the motor.. My question now is how much play do these slots allow? I can't find a drawing anywhere with dimensions for the holes. How do you gauge the correct height to put the inner plate without the motor in place for reference? I cant loosen the bolts without taking out the motor and the Y pipe, and would love to be able to set it and forget it after taking all that off the first time. Thanks in advance for your help

In all the years working on mercs I have never seen any slots in a inner plate . Only holes / There is no engine height adjusting on a inner plate. Post some pics of what you have ,

Wide a** wake said:

Ok, I am sure there were no 1/2 inch pads. After messing around with this all day today, I think I see where the problem is. I put the motor back in, and took the double wound washers out. The spline was closer to inserting in the coupler, but still a long ways off. I took the old transom plate, and measured the thickness of the "ears" where the bell housing mounts sit. The new one was 1 or 2mm different, but that should not throw me off as far as I am. Then I noticed that the inner transom plate is slotted, and therefore adjustable up and down to some extent. So, tomorrow I will take the motor out (again) and move the plate down to lower the back of the motor.. My question now is how much play do these slots allow? I can't find a drawing anywhere with dimensions for the holes. How do you gauge the correct height to put the inner plate without the motor in place for reference? I cant loosen the bolts without taking out the motor and the Y pipe, and would love to be able to set it and forget it after taking all that off the first time. Thanks in advance for your help

Click to expand...

I tried to attach photos of the old inner transom plate, but the attachment interface on this forum is so clunky that it just took years off my life with the frustration. The old plate has holes, but they are not completely round. In fact, they have the same shape as the holes in the feet of the front motor mounts on the sides of the motor, and I am sure for the same reason if you need to adjust slightly to locate the lag bolts in the best position to secure the motor to the floor. I looked at some parts diagrams, and the holes have the same appearance in the drawings. In any case, If nothing else I will install the old transom plate because I know that one was working with the application before the pin bracket got broken.