Volvo gear ratio? How do I know?

[lyt]

Interesting thought.....

I feel like I am not getting the correct cruise and top end out of my engine/drive. I always assumed I had a 1.95 ratio on my outdrive....

Basically I want to know for sure so I can eliminate that variable in the equation .....

Is there an easy way to find this info? some test?

 

[Bondo]

Re: Volvo gear ratio? How do I know?

Interesting thought.....

I feel like I am not getting the correct cruise and top end out of my engine/drive. I always assumed I had a 1.95 ratio on my outdrive....

Basically I want to know for sure so I can eliminate that variable in the equation .....

Is there an easy way to find this info? some test?

Ayuh,... It'll be a whole lot Easier if ya tell Us what yer motor, 'n drive Are....

 

[QC]

Re: Volvo gear ratio? How do I know?

The only real way if you don't pull her apart and count gear teeth is to put her in gear and bar the engine over and count how many times the prop goes around. If you bar her over 10 revs, the prop should go around 5.1 times. 10/1.95=5.12 etc.

A simpler way would be to get us your RPM, prop pitch and GPS speed. Trimmed out as fast as she will go. Tach has top be dead nuts right, and they often aren't. Get us what you have and we can at least tell you if you are close.

Edit: Yeah, if she is new, then Bondo is right. I guess I was thinking something that has been around for a while and could've been changed. But don't be stingy with the info. Mo info = mo betta answers.

 

[lyt]

Re: Volvo gear ratio? How do I know?

lol....

yeah....

duh...

DP-A Drive with volvo 570 -- however I bought it only last year and suspect drive has been rebuilt...but no way to really know

 

[lyt]

Re: Volvo gear ratio? How do I know?

~20 knots cruise @ 3000

~30 knots WOT @ 4000-4100

props are b4 duoprop

cannot get over 4100 RPM. This is why I am trying to fix....I want to get 4600 which is proper WOT

 

[Don S]

Re: Volvo gear ratio? How do I know?

There should be a tag on the upper gear box with the gear ratio on it.

If it's all OEM, you can remove the anode on the lower unit in front of the props and look at the bearing carrier. It has the ratio stamped in it.

 

[lyt]

Re: Volvo gear ratio? How do I know?

drive worn...no tags....

not 100% sure all OEM....

 

[Don S]

Re: Volvo gear ratio? How do I know?

If you bar her over 10 revs, the prop should go around 5.1 times. 10/1.95=5.12 etc.

It would be a lot easier to turn the engine 2 turns, and a prop would turn just a hair past 1 turn. (if you could even see that hair)

 

[QC]

Re: Volvo gear ratio? How do I know?

What we really need is another Mod to reply

Boat?

Edit: I agree, Don. Was trying to explain the math. I guess it depends on how close up or down the next ratios are. More revs = more accurate.

 

[lyt]

Re: Volvo gear ratio? How do I know?

drive worn...no tags....

not 100% sure all OEM....

 

[lyt]

Re: Volvo gear ratio? How do I know?

yeah i will just turn the engine... duh...

sometimes the simplest answer is the most profound

 

[Don S]

Re: Volvo gear ratio? How do I know?

Just make sure you put it in gear and get all the "Slop" out of the gears before you start turning and counting.

 

[lyt]

Re: Volvo gear ratio? How do I know?

ok... turning this engine aint so easy.... no bolt.... let me devise another plan....

 

[lyt]

Re: Volvo gear ratio? How do I know?

ok... well....

turning this engine is a tad difficult due to its position in the bilge.....

 

[lyt]

Re: Volvo gear ratio? How do I know?

going to try a strap wrench.....

 

[QC]

Re: Volvo gear ratio? How do I know?

Pull the plugs . . .

 

[Don S]

Re: Volvo gear ratio? How do I know?

Pull the spark plugs, tighten the belt and turn the nut on the alternator.

 

[lyt]

Re: Volvo gear ratio? How do I know?

oh man..... sounds like fun..... you guys obviously have not seen my bilge space

 

[Don S]

Re: Volvo gear ratio? How do I know?

Well, you could always pull the outer shaft out of the lower unit, the gear ratio should be engraved in the side of the shaft..

 

[lyt]

Re: Volvo gear ratio? How do I know?

Ok,

Let me just ask you this.... Because It isn't adding up......

Here is the boat and info:

1990 Wellcraft Sportsman (cuddy)
Penta 570 carbed ....holley 650 cfm
DP-A outdrive
3380 Dry weight
4440 lbs. with I/O

less than 1/8 tank (about 20 gal) non -ethanol fuel
Myself about 200 lbs.
and about 200 lbs max gear onboard

I run about 3000 rpm and reach 20 knots
My WOT is 4100 and reach about 30 knots ( I have my gps set to do knots not mph)

Props are b4 Duoprop.... Aluminum

Sure it could use a bottom paint....

-----------------------

So here is the deal

I have been looking at some numbers from other boats with the exact same setup, and most of them are doing significantly better and with b6's 24' boat cuddy ....Total weight about 6000 lbs. and he is running 34 mph at 3200 cruise and 42 mph WOT.

EXACT SAME SETUP.

Now, I do know that different hulls do better.....

I am testing in relatively calm waters....and really feel like something is not right..... and I'm trying to determine the cause.....

either props, or it needs a tune....