Mercruiser 5.7L engine with a 1.84 outdrive. Prop suggestions.

[dbohnett]

1988 GW Invader 200ss. Dry weight 2400lbs. Boat started out with a 4.3L and a 1.84 outdrive. I bought it recently with a blown 5.0L but still has the 1.84 drive. A 14.25 x 20 3 blade prop was on the boat when I purchased it. Am going to install a 5.7L. Can I still use the 1.84 drive if propped correctly or will I need to go to a 1.47 drive? Thanks for any help.

 

[Scott Danforth]

I would look for a 1.62 or 1.47

 

[QBhoy]

You might be on the verge of being close to the top end of the off the shelf available prop pitching. Be close anyway. Be at least a 23” you’ll need or more perhaps.
Just roughly…if she can be estimated to achieve early to mid 50’s gps…at say 4800 rpm..say about 10% slip…you’ll be at 25” of pitch. That’s generally the top end of the normal easy to get props. Probably be ok if you’re within that. Most likely will be…but mechanically speaking…yeah…it’s not ideal really. If you see a cheap 1.6 alpha, be ideal. With the 1.47 ratio.. you’ll do well to turn a 19” well enough into the range. Most likely be a 17” you’d need for that. Again..close to the opposite end of the range. 1.6 ratio would have you with plenty breathing space either side.

 

[Scott06]

It might work. I did a 4.3=> swap and kept the 1.81 V6 drive, just stepped up from 19" to 21" pitch (3=>blade). At the time the boat only had 37 hours on it so I hated to swap the drive out for the 1.62 it should have come with

A 23" pitch might work especially if it is something that has cup and grip like a Revolution 4 or Enertia. Since you already have the drive I would try it out if you can find a prop shop that will let you swap some props. You can always buy the drive if it doesn't work.

 

[Scott Danforth]

can also zero balance the motor and run better valve springs. then the limit on RPM's is teh cam and intake.

 

[dbohnett]

Thanks for the help. Would like to change the drive. The one on it is pretty crusty. Will look for a 1.62. I,m in Michigan so hopefully can find something and test it in the water before I'm froze out.

 

[Scott06]

You can change just the upper if your lower is still ok. All the gear ratios use the same lower

 

[dbohnett]

Thanks for the reply. The whole outdrive unit seems to be working correctly, turns and engages forward and reverse properly. If I can get just the upper at a better price will do that. Thanks again.