mercrusier 5.7 vs 7.4

[cpt ron jc]

I have a 1990 larson 25 ft 5.7 alpha set up ,i was looking at a 7.4,1993 brov. would this work wt.difference/hooking up what will have to change if anything.mercrusier

 

[alldodge]

I have a 1990 larson 25 ft 5.7 alpha set up ,i was looking at a 7.4,1993 brov. would this work wt.difference/hooking up what will have to change if anything.mercrusier

If your talking about swapping the 5.7 with the 7.4 in your current boat, it will work but...... there is always a but. You will need to move your motor mounts and change everything out, including transom assembly

 

[cpt ron jc]

oh boy a can of worms i think to much to change 5.7 is what is in boat now go with the same.ty

 

[Bondo]

I have a 1990 larson 25 ft 5.7 alpha set up ,i was looking at a 7.4,1993 brov. would this work wt.difference/hooking up what will have to change if anything.mercrusier

Ayuh,.... Are ya lookin' to just swap the motors,..??

I ask, because you mention gettin' a 7.4l, 'n the Bravo drive,.....

A pulleys to prop swap is fairly easy,....
Easier than puttin' the 7.4l, in front of an Alpha,....

 

[cpt ron jc]

yes ,i have a 90, 5.7 with an alpha drive,the motor i was looking at is a 7.4 yr 93 bravo motor,wt/ width ,drive what needs to be changed,or will it be one big pain thanks. yes swap motors mine is toast

 

[alldodge]

yes ,i have a 90, 5.7 with an alpha drive,the motor i was looking at is a 7.4 yr 93 bravo motor,wt/ width ,drive what needs to be changed,or will it be one big pain thanks. yes swap motors mine is toast

You can put that 7.4 on the alpha drive without changing the transom, but you can not put a bravo on a alpha transom assembly. So just swapping motors would be easier

 

[Tail_Gunner]

If its a typical stock 7.4 your probably better off runing a new 383 more horsepower and probably as much tourque.

 

[thumpar]

If you keep the alpha drive and get a motor with more horsepower be careful with the throttle hand. The Alpha is only rated for 300hp.

 

[cpt ron jc]

well the price is right its a good engine,i figure i will have more power its a heavy boat,will talk to my merc. shop first.thanks

 

[thumpar]

If you do it go with the Bravo drive. You will love it.

 

[achris]

Heavy boat... 7.4litre engine... Alpha drive.... Good-night drive!

Swap the complete power package, as Bondo said, pulley to prop. You can't bolt a bravo drive on an Alpha gimbal, so you need to pull the transom housing out and swap that too...

 

[cpt ron jc]

I was trying to avoid changing gimbal,/drive,at reg. rpm not pushing it what do you think,are rpm that much more.

 

[achris]

I was trying to avoid changing gimbal,/drive,at reg. rpm not pushing it what do you think,are rpm that much more.

It's not the revs, it's the torque the engine produces, and a heavy boat will require that much more torque to be transmitted... And maximum torque is require just as the boat rises up onto the plane. The Alpha drive will not handle it...

BTW, it's no big deal to change the gimbal housing. You need to remove the drive to remove the engine. Once the engine and drive are out of the way, pulling the old gimbal housing is about a 1 hour job. You may need to drill 2 new holes at the top of the cutout, then fit up the Bravo Gimbal housing, another 2 hours.... All in all, not as hard as even pulling the engine...

Chris....

 

[cpt ron jc]

Thanks i got it now i will have to decide if i want to go through, i know bravo parts$ i can find alpha parts any where

 

[Scott Danforth]

you can also find Bravo parts anywhere they sell Alpha parts. if it was me and I was in your shoes, I would do the swap in a heart beat. not only would the pork chop motor be installed, I would probably change the cam and put on a seletable exhaust.

changing the transom shield and gimble assemly is simply unbolting one, drilling 2 holes, bolting on the other.

 

[JaCrispy]

You'll want to pull the gimbal for piece of mind anyway. I found lots of bad things when I removed mine. Rotted lower transom bolts, hole in the Y pipe, warped water tube, various bad seals, etc. Not to mention the regular things like replacing the bearing and bellows.