Outdrive Gear Ratio

[FULL-THROTTLE]

Hello,
I am having my outdrive rebuilt and I mainly using the boat for wakeboarding and skiing, presently it has a 1.5 gear ratio in it and the boat is a little slow coming out of the hole, is there a recommended ratio I should go with for watersports? I have a 260HP v8 5.7l mercruiser with a 14" 18 pitch prop and at WOT it is at 4600-4800 depending on how many people in the boat. The boat weighs 2800lbs empty.

I am also thinking about a new cam, heads, edekbrock airgap intake and 650 carb will help.

Thanks

 

[Gimme Fuel]

The gear ratio in the drive is fine. For a better hole shot you should drop down to a lower pitch propeller. Much easier and cheaper than a new gear set. You should find a prop with a decent hole shot on your boat for doing watersports and have another for top end runs and cruising. Decreasing pitch will also raise yuor rpm's.

 

[Gimme Fuel]

If you are thinking about adding power to your motor, you will more than likely need to re-prop also. So, decide on your prop after you have the motorwork done. You can accomplish what you are asking without having the motor built, you just wont go as fast on the top end.

 

[Wide Open]

What brand and model boat? I'm guessing that coupled to a 5.7 carb engine, it's likely an older Alpha "One" drive as they were widely used in a 1.50:1 ratio some years ago.
As GF mentioned, your WOT RPM is spot on (considering that you are reaching it under normal load and weather conditions). If you opt to not do the engine mods, try looking in to a 4 blade prop in the 16 pitch range, or possibly a large diameter 3 blade. Down in the 15-16 pitch range you'll likely find a "pontoon" style prop with a large blade surface area and 15" or so diameter. The boat won't run fast, but you'll be impressed with the stump pulling thrust it will offer, which sounds like what you're looking for.

 

[FULL-THROTTLE]

1990 Ebbtide

I have a 1990 EBBTIDE Campione 204. Big boat and heavy. As mentioned above about dropping down a prop pitch size, I had a 17 and it would over rev, 5000 rpms, I can't go with a larger diameter prop it won't fit. HMMMM a 4 bladed prop might be the way to go???

Thanks.

 

[FULL-THROTTLE]

CAM

I really think a new cam and intake will help. I need to play with something this winter and some performance parts would be fun.

 

[Wide Open]

Try a Mercury Alpha 4 (Part number 834850A45). That's the part number for the 16" pitch right hand rotation prop. It's a 15" diameter prop, but it will fit your Alpha drive.......with one exception. If your drive still has the zinc trim tab under the cavitation plate, you'll have to cut the "fin" part off for proper clearance. A flat plate zinc anode (part number 76214Q5) is available, but it only fits Gen II Alpha drives. Based on the year of your boat (1990), I can't determine if your drive is a Gen I or Gen II without the serial number.
The Alpha 4 is a great prop, and in my opinion, very under-utilized. It's a 4 blade aluminum design that performs well for your application. And since it's aluminum.....it sells for $216.05 retail.

 

[FULL-THROTTLE]

Prop

Thanks for the recommendation I will give it a try, unfortunately I will have to wait until may to let you know how it works.

 

[yellowfiero88]

I've heard some really good results out of the 5 blade prop for water sports. I think that they are called "high 5"

 

[Wide Open]

The "High-Five" is an outstanding prop for pulling and any kind of watersports! However, it also sells for $671.50 retail. That makes the Alpha 4 aluminum 4 blade really attractive.

 

[FULL-THROTTLE]

1991 4.3 outdrive??

I have an opportunity to pick up a complete boat, 1991, it has a V6 4.3L and I believe it is a 1:81 gear ratio, is there any reason this won't work on my 1990 boat? I realize I will have to change the entire outdrive, gimbal ect and re-prop for the gear ratio difference. My present boat has a 1:5 gear ratio with a 19 Pitch 3 bladed prop, I will probably be increasing the new prop to a 21.

P.S. I just found out the gimbal bearing is bad on my existing outdrive, the steering shaft has significant movement in the gimbal bearing, I tried tightening the 2 thru bolts and it did not help at all.

Thanks

 

[FULL-THROTTLE]

Correction

I meant Gimbal housing/assembly is bad.

 

[Gimme Fuel]

Chances are that Gimbal Assembly will be worn and need attention too. By the time you change outdrive then prop back up to correct RPM, you haven't changed really anything. It is the same as putting a lower gear ratio in your truck and adding bigger tires. The net result is the same final drive ratio. What you are talking about doing is a lot of work...you must pull your motor, remove entire gimbal assemble, reseal, and replace with the other one which may not me in any better shape.

You are better off having your gimbal assembly rebuilt or buying a refurbished one. The only way you will be able to pull a skier better is to drop pitch and add blades for traction or increase horsepower to turn your current prop faster. You would be impressed stepping down to a 16-17 pitch 4-5 bladed prop. It makes a huge difference. This is not a care where it is better to buy the whole cow if you want a glass of milk. Make the simple prop change and see if you like it. You will never have one prop that can pull a skier well AND give good top end. It doesn't work that way with boats that have fixed ratios unlike a car where you can run in a lower gear if you are towing.

 

[FULL-THROTTLE]

Gimme fuel, very good point, I will pull the outdrive off and take a look. I know I have to change the steering shaft and lever I have 8 inches of left and right play in the outdrive after retorquing the steering shaft retaining bolts. It will be a nice winter project. I never used a 4 or 5 bladed prop so it time to find out.

Thanks Again.

 

[Gimme Fuel]

Also check the tightness in your rack and pinion/steering cable. Those wear out too and may be contributing to the slop.