Mercruiser 220 mpi repower

K

Kinkchaser

New member
Just repowered my 1990 v20 with Mercruiser I/O 220hp MPI. Only getting 22.5 knots at 3600 rpms with a 15x17 4 bladed aluminum prop. Any thoughts what my cruise speed should be? With 220hp, should be doing better than 22-23 knot cruise in my opinion.
 
Make sure you have the correct t outdrive ratio. Should be 1.84( or close to that number). You can crutch the issue with lower pitch props,but it will run better with the correct t ratio. Has the engine been checked by a knowledgeable tech? Does it have cat exhaust? New engine or uses? You have bottom paint?
 
This question is for Spareparts, I have a 15x17 3 blade prop and is perfect for my 150 mercury outboard. What would it be if I put on a 4 blade prop? Same pitch and diameter. . What is the difference
 
Generally you step down one pitch going to a 4 blade,unfortunately most aftermarket 4 blades are way underrated trying to make their props seem.more efficient. Powertech is notorious for this, I've had to step down 4 inches to get close to what I started with on a 3 blade. The reason I recommend a mirage is it's a true standard for reference. It may not be the best prop, but it's the best one to start with. Getting into diamter,rake,and cup can make a big difference as well
 
Step, I don't know much about props, but on my ProLine, in the picture, if I remember it was a 3 blade Bravo. I wouldn't know what the difference is between the two, maybe just the name, but she ran like a charm. Again. just my lousy 2 cents. 🇺🇸 ❤️ 🇺🇸 ❤️ 🇺🇸
 
spareparts said:
Make sure you have the correct t outdrive ratio. Should be 1.84( or close to that number). You can crutch the issue with lower pitch props,but it will run better with the correct t ratio. Has the engine been checked by a knowledgeable tech? Does it have cat exhaust? New engine or uses? You have bottom paint?
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This is the 2nd 220hp MPI Mercruiser I had boat repowered. Last one was 2004. That setup with 3 blade prop same diameter and pitch was about 23.5kn. Installer said I was getting the correct rpm’s. One technician mentioned if I go up to a 17x19, I’ll give up top end but midrange should be better. Not looking to be a speed demon, but feel the boat with a 220 I/O should get 25-26 knots. Motor is brand new with warranty and used same Alpha drive. Not sure the ratio. Boat gets up on plane quicker and runs smooth with the 4-blade but seems to be 1 knot less at 200 rpm’s more.
 
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