mercury rev 4 vs mercury trophy plus

[sparkyaber]

Does any one know the difference between these two props?

I need to replace my 3 blade tempest because of blow out issues, and was told to try a 4 blade before I think of a jack plate. Now I just need to figure out which one?

[Capt. Don*]

I have rev 4's as well as 3 blade mirage plus. I run a heavy offshore boat w/twin 225's. The 4's give me more traction if you will and get on plane very quickly, very good lift on the stern, but I sacrifice fuel economy. I run 70-90 miles per trip so fuel consumption has to be factored in, I went back to the 3 blade mirage+ and get good results but need to run a little faster to hold on plane. Go to www.mercurymarine.com and use the prop selector tools, you can get a good start on what may work well for your needs.

[sparkyaber]

I did try their prop selector tool and it really didn't work. It asks all of the information, and then I get an error saying that my pitch or top speed is out of expected range. My boat is very light so I can get away with running a high pitch prop and I think that is the problem with the program. I had to reduce my top speed 10 mph to get it to work.

[Whoaru99]

What is the operating condition when it happens?

[kjgmh]

If blowing out with a tempest I would stay away from the trophy, it is a small hub and probably would not work better. The Rev 4 would probably work better for you.

[sparkyaber]

It does not matter where the motor is trimmed up down in the middle any corner with excelleration it will blow out. Really tough to pull a tuber or skier with this happening.

[Whoaru99]

Sounds more like ventilation than blow out.

How high is the engine mounted?

Is the anti-ventilation plate equal to, higher than, or lower than the bottom of the boat?

[hydro]

Your problem is cavitation (ventilation), caused by the prop sucking in air during turns. The suggestion above about engine height is a place to start since having the prop too near to the surface will cause what you have described. Try putting a straightedge on the bottom of the boat and measuring from the center of the prop to the straightedge. This is propshaft height and is the baseline to diagnose your problem. Post is back and we can help you fix things before you throw money at a new prop.

[sparkyaber]

Yeh, that was the first thing I checked- I am 5 and one half inches below the pad with my prop shaft height. (center point of the prop shaft compared to the bottom of the boat.) I was informed that 3 inches is about the place to start and work from there. I can only go one hole farther down with the motor I am in the second to the top hole. With the addition of the 4 blade it stopped the blow out almost all together I had to try to make it blow out.

Thanks

Set up:

Triton fs190

mercury opti 200

23" tempest plus

66mph + running about 5300rpms

I could never get the boat all the way trimmed out beacause the boat would start to chine walk.

When I put the rev4 23" I could only get 60mph and running about 5200r's, but could get the boat all the way trimmed out.

I am trying the 21" rev4 tomorrow. I have heard you can get a "blowout ring" to use with the trophy to make up for the small hub.

Thanks for the help!

[hydro]

Sparky,

This may give you a little info for comparison. I'm running a 20' Coral Fish and Ski hull, basically a pad vee hull similar to your boat and probably about the same weight. My motor is a 200EFI Mercury with a Tempest 23" three blade set to 3 1/4" below the pad. With this combination I get some cavitation on takeoff unless the motor is trimmed in but overall it runs very well. when I first got the boat the motor was set up like yours at about 5" below the pad and it chine walked bad. Raising the motor cured the chine walk completely. I still notice some cavitation on hard turns with the motor trimmed up but if I pull it down I can corner hard.

Keep up the experimenting and You'll get it figured out!

[sparkyaber]

how much of a differance is there between raising the motor vertically and trimming it up. if it is really important I think I will be investing in a jack plate.

I tried a 21" rev 4 tonight and also a enertia 22". The rev 4 was close, but chine walked at about 50 mph- I did get it to 60.5 mph @5600 rpms, I was by myself, and with just me in the boat, with the batteries on the same side it really leans to the right side.

The enertia was not good, hit the rev limiter very easily, and only got 60.7 mph out of it.

The rev4 was impossible to get air under the boat, if I tried I could get the enertia to blow out.

[hydro]

Sparky,

A couple of thoughts on your last post. First, there is a BIG difference between vertical adjustment (propshaft height) and trim. The trimming the motor will act like a lever, lifting the bow and, to a point, reducing wetted hull area and friction. The result is you will go faster until the trim gets too high and you wind up just throwing water in the air. A good indication of trim is a rooster tail about 6' high at WOT. A vertical jackplate will allow you to raise the motor on the transom, reducing the frontal mass of the gearcase, and also getting the top of the propeller free of the water. If you are still having problems with chine walking this is the solution. Also, the prop must be designed to operate in a semi-surfacing condition. The Tempest works well here.

You have also mentioned that you are seeing RPM in the 5300 to 5600 range. What is the recommended WOT range for your motor?

Another detail I thought of this morning is that you started out with a Tempest Plus prop. Were the vent holes plugged or open? They are designed to allow the prop to ventilate during the hole shot and get the motor into it's power band quickly. If too much of the vent hole area is open there will be excess exhaust over the blades of the prop and you will see all sorts of ventilation problems.

Good Luck,

Hydro

[Whoaru99]

If you get a jack plate (or start raising the engine much), be sure to get a water pressure gauge if you don't already have one. The higher you raise the engine, the more chance to suck air into the water intake.

[hydro]

If you start to lose water pressure you can plug the top water pickup holes to prevent air from getting in. Mine are plugged and it worked slick. To plug them just tap the hole for a 5/16" setscrew and be sure to use loctite when installing the plug.

Also, if you put in a water pressure gauge it will probably freeze during storage and be destroyed. A gauge isolator or simply removing it prior to storage will protect it.

[sparkyaber]

Sorry to take to long to get back to this post- slayed the kings over in michigan this weekend.

WOT is supposed to be 5000-5750, but I would like to get close to the highest rpms possible.

Vent holes- Med holes in place now, kept them in in each prop that I tried.

I have never had a rooster tail with this boat.

I do have a pressure gauge on this boat, and I run 15-20 psi when flying across the lake.

[hydro]

With what you have posted, I suggest the following:

Raise the motor so that the prop shaft is about 3 ½” below the pad. Try the Rev 4 again and I bet you will pick up some RPM and MPH. (You mentioned that the 21” Rev 4 ran 5600 RPM and did not ventilate) Try the Tempest again at that motor height and evaluate the two props for the best OVERALL performance (not just speed).

Good luck.

[sparkyaber]

I think I will be getting that jack plate. I don't want to take the boat to the dealer to move the motor up and find out I have to move it back down. $$$$ I was thinking that the rev4 would be the one, now I have to decide if it will be the 23" or the 21". I am pushing the upper limits of the recommended r's with the 21, and if I raise the motor I am afraid I will go over the 5750 that is recommended. How many rpms do you think I will gain buy raising the motor with a jack plate?