imongo

I have a 35 Cafe Racer and am trying to get two things sorted out. The first is props. Power is 454 465 hp on Bravo 1. The boat came with 21 Mirage. Goes right to the rev limiter at about 60 mph. Tried 21 pitch Rev4. A tad faster. I am considering Bravo 1 4 blades at 22 pitch. Would this be a good choice? What gain in performance might I expect?

The second is drive related. One of my drives' reservoirs gains and looses it's lube level. When the boat is cold the level is at the "full" line. When I run the boat the level rises almost to the point of overflow. Then, the next day the level goes back to normal. I wouldn't think anything of it (expand when hot, contract when cold) but the other drive doesn't do this. Any ideas?

Mongo

rjcardinal

Cant help you on the props, no expeirence on a boat that big.

Its normal for the oil level to go up some when the oil is hot. If it seems excessive there might be an air bubble in the drive case or hose somewhere. Have you changed the oil in them lately? Is that when you noticed the high level. If the other one is not doing it the hose may be plugged. I had a hose plug once when I had some condensation in the resevoir.

If you havent changed the drive oil lately it may be a good time to do it now and clean the reservoirs and hoses. I refill the drive with the pump from the bottom untill I get some out the vent hole. Then I replace the vent cap and keep pumping until I fill the reservoir. After a change I have noticed erratic oil levels in the reservoir for a while, then it seems to settle down.

Ron

mcollinstn

You have 365hp 454's, not 465hp.
You should prop the motors for 4900-5000 rpm.
Mirage 3 Blades will probably give you the best topend mph. Bravo1 4-blades will suit you better if the Mirages ventilate too much to suit you when coming onto plane.

Pitch will be determined by engine RPM. You will have either 1.5:1 or 1.36:1 ratio drives (I don't know what was spec'ed form the factory and do not know if somebody has swapped them so you will have to find out on your own).

Bottom line, though, is to prop for 4900 to 5000. You will then have the correct prop pitch.

Judging from your excessive rpm at 60mph, I will assume you have 1.5:1 ratios.

As far as the drive lube level, you definitely have an air bubble in the drive. As ron suggested, you will need to drain the lube out form the bottom (remove the reservior cap before you unscrew the bottom plug). After draining, refill from the bottom at down trim. This forces air out the reservoir tube.

M

imongo

Thanks guys.

The hose that runs from the drive to the reservoir had a loose clamp on it so it dumped the gear lube in the bildge. After I tightened the clamp and refilled the reservoir is when the level started to change. I'll do the drain and clean thing.

M on the prop thing. Yes the gear is 1.5. How much of a speed/performance increase do you think I'll get by going to a 22 pitch lab finished bravo 1 over the 21 pitch Rev 4's that are on the boat now? Yesterday the GPS read 61 mph at 5000 with the bimini up and full tanks of fuel (I was going downwind with a 15 mph tail wind).

Thanks again for your help with this!

Mongo

kook

I wouldn't lab the Bravo1's, at least not to start. They're really not a full 22 pitch. Try them stock before looking into getting lab'd. No experience with the Rev 4's, but you should see midrange (cruise) performance increase with the Bravo1's, compared to the 3-blade prop.

Mbam

imongo, a Rev pulls 300 RPM less than a Mirage plus of the same pitch. so -

21 rev = 5000 RPM, that means a

21 Mirage = 5300 RPM, a 22 Bravo one pulls about the same RPM as a 23 Mirage, each inch in pitch is worth about 200 RPM, so

22 Bravo 1 = 4900 RPM

A Revolution might be faster then the Bravo's on your boat, but you won't know unless you try. My guess is that as far as top speed, a pair of 23 Rev's will do it. Whatever you try, it is best to find the style of prop that works best and then have it labbed and tweaked as needed.

mcollinstn

yeah, if you are at 5 grand with the bimini up and full tanks, then you certainly could use some more prop.

23's in the Rev or Mirage, 22s with B1s. Try em all. Pick a day where the weather is expected to remain steady. Try each set and record planing behavior, cruise speed at a set rpm, topend mph and rpm and trim setting, "bite" during docking maneuvers, and overall handling. Try each set of props turning BOTH directions ("in" and "out"). Your boat will handle differently with each combination. In addition to the outright topend mph, there are other factors that wil affect your decision...

I've got some Mirage 23s you could try, but you need to try to hook up with somebody local. If you find a prop service that has a reasonably high volume of work thru there, you can usually buy a truckload of props on a credit card and go play. I deal with a guy who lets me return whatever I don't like. If I ping one, I pay a rework fee. (I never borrow NEW props, only reworked ones - If you ping a new one, there's a $100 fee on top of the rework fee cause it is now a used reworked prop).

imongo

Again, thanks for all your help!!!

The Rev 4 is a new prop to me. I like the way it performs. Great out of the hole and superb in the mid and turns. No ventilation anywhere. Is this Merc's "new" Bravo 1?

Can the 21's I have on the boat be re-pitched? The guy that owns them wants my 21 Mirage's, so it would make sense to do a swap and have them re-done (if this makes sense $$$). I have a friend with a Scarab that has 23 Mirage he offered to test. I am in the Virgin Islands so a prop shop around the corner is not an option. Thanks for the offer "M", but the frieght would kill me.

Let me know about anyone that might be able to change the Rev 4's I have and maybe tweaking them for best performance.

Thanks for all you help!!!

Mongo

mcollinstn

Urgh,

Repitching is usually cost prohibitive unless you have seriously mangled props to start with (in that case, it is cheaper than replacement but not a whole dang lot).

I would think that a swap would be a far better option, assuming you could find a body wanting what you have and having what you want...

Do you have a prop shop local to you? Go talk to the guy. He may have recommendations..

m

imongo

Hi M,

No prop shop anywhere in sight. It will be just as easy to ship them to the states (I'm in the Virgin Islands). If I get the props for free it will make sense to re-pitch.

Now for the question...

Lets just say I am in the market for new props. I know I need a 23 pitch 4 blade. Do I go for the Rev 4 or the Bravo 1 and why?

Mongo