Baja 272 454MPI (310 hp) Prop
#1
Registered
Thread Starter
Baja 272 454MPI (310 hp) Prop
Hello,
I have the boat and engine above and I took it out to get a good GPS speed before the end of the year so I can either lab or order a new prop for next year. It was me, the wife, 1/4 tank of fuel, and pretty good water. Trimmed all the way up I was able to tap 56 but it was only for a couple of seconds. With the throttle in the dash I was only spinning 3900 RPM. I have read that these boats should spin 4200 so I am curious what y'all think I should do with my prop. It is a 23P Mirage Plus. Also once I get to around 3/4 throttle there is really no change in rpm going further.. Not sure if that is prop related or cable related, but I am sure someone on here would know. Let me know if there is any other information you might need.
Thanks!
I have the boat and engine above and I took it out to get a good GPS speed before the end of the year so I can either lab or order a new prop for next year. It was me, the wife, 1/4 tank of fuel, and pretty good water. Trimmed all the way up I was able to tap 56 but it was only for a couple of seconds. With the throttle in the dash I was only spinning 3900 RPM. I have read that these boats should spin 4200 so I am curious what y'all think I should do with my prop. It is a 23P Mirage Plus. Also once I get to around 3/4 throttle there is really no change in rpm going further.. Not sure if that is prop related or cable related, but I am sure someone on here would know. Let me know if there is any other information you might need.
Thanks!
#2
Charter Member #1171
Charter Member
To much prop for that boat. Thats what I ran with a 502 MPI in our old 272.
Try a 21 M/P or get that one turned down a bit and labbed.
Quick cable check, go WOT on the dash and verify at the plenum that you cannot pull the throttle arm anymore.
Try a 21 M/P or get that one turned down a bit and labbed.
Quick cable check, go WOT on the dash and verify at the plenum that you cannot pull the throttle arm anymore.
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#3
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Thread Starter
Anyone in the DFW area have a 21P MP I could borrow for a day??
Thanks for the help!
#4
Registered
We have a 7.4 mpi (310 hp) Bravo 3 (1:2 ratio) pushing a 226 Cobalt - we can easily hit 60 MPH on GPS and WOT is 4600 rpm's with 2 people in the boat at about 25 gallons of fuel. We are spinning 3 blade 28P props.
I know it's late in the season - and we really can't compare Bravo 3 - dual prop to a Bravo 1 but it seems to me that I would start with the basics - were all the connections tight on the electronics - Ours is a 2000 year boat also and every once and a while gauges will get a little squirrely only to see a little corrosion on a terminal- once removed all is well. Was the air intake clean - a 7.4 goes thru a lot of air each revolution and anything that restricts this could cause a decrease in performance.
The second I would do I check the throttle linkage - are you really opening it up - sometimes these can get out of adjustment.
Please let us know what happens
All the best
3pointstar
I know it's late in the season - and we really can't compare Bravo 3 - dual prop to a Bravo 1 but it seems to me that I would start with the basics - were all the connections tight on the electronics - Ours is a 2000 year boat also and every once and a while gauges will get a little squirrely only to see a little corrosion on a terminal- once removed all is well. Was the air intake clean - a 7.4 goes thru a lot of air each revolution and anything that restricts this could cause a decrease in performance.
The second I would do I check the throttle linkage - are you really opening it up - sometimes these can get out of adjustment.
Please let us know what happens
All the best
3pointstar
#5
Registered
Thread Starter
We have a 7.4 mpi (310 hp) Bravo 3 (1:2 ratio) pushing a 226 Cobalt - we can easily hit 60 MPH on GPS and WOT is 4600 rpm's with 2 people in the boat at about 25 gallons of fuel. We are spinning 3 blade 28P props.
I know it's late in the season - and we really can't compare Bravo 3 - dual prop to a Bravo 1 but it seems to me that I would start with the basics - were all the connections tight on the electronics - Ours is a 2000 year boat also and every once and a while gauges will get a little squirrely only to see a little corrosion on a terminal- once removed all is well. Was the air intake clean - a 7.4 goes thru a lot of air each revolution and anything that restricts this could cause a decrease in performance.
The second I would do I check the throttle linkage - are you really opening it up - sometimes these can get out of adjustment.
Please let us know what happens
All the best
3pointstar
I know it's late in the season - and we really can't compare Bravo 3 - dual prop to a Bravo 1 but it seems to me that I would start with the basics - were all the connections tight on the electronics - Ours is a 2000 year boat also and every once and a while gauges will get a little squirrely only to see a little corrosion on a terminal- once removed all is well. Was the air intake clean - a 7.4 goes thru a lot of air each revolution and anything that restricts this could cause a decrease in performance.
The second I would do I check the throttle linkage - are you really opening it up - sometimes these can get out of adjustment.
Please let us know what happens
All the best
3pointstar
I keep the air cleaner as clean as possible. It gets dirty pretty quickly. Just swapped plugs,wires,distributor cap, and rotor at the beginning of this season. ( the boat was only spinning these RPMs last year also from what I remember) It sounds strong and runs great. I do believe i need to replace my IAC but other than that no issues I can see.
#7
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Thread Starter
#8
VIP Member
VIP Member
In the future refer to it as 7.4 MPI, it eliminates confusion with other engine models. Your RPM range is 4200-4600. A 21 Mirage + should get you right at 4200-4300. We had a 23+ and it lugged when the engine was stock, like what your experiencing. I had BBlades work the prop to get it to spin but for the $ you can just buy a new 21. Dont expect much more speed, youll be right at 58-59. Thats all we could get in stock form. Your engine will be under less stress also.
#9
Registered
Thread Starter
In the future refer to it as 7.4 MPI, it eliminates confusion with other engine models. Your RPM range is 4200-4600. A 21 Mirage + should get you right at 4200-4300. We had a 23+ and it lugged when the engine was stock, like what your experiencing. I had BBlades work the prop to get it to spin but for the $ you can just buy a new 21. Dont expect much more speed, youll be right at 58-59. Thats all we could get in stock form. Your engine will be under less stress also.
#10
Charter Member # 55
Charter Member
You want to prop it to spin close to 4600 rpms for best performance. The WOT range of the engine is 4200-4600 rpms.
I also highly doubt your speed is an accurate GPS speed.
I also highly doubt your speed is an accurate GPS speed.