Right lower unit

[adray1]

I have a 1985 Baja Force 200 with a mercruiser 260 with a alpha1 lower unit. The boat weight is 2800#. I have a 1.84:1 lower and I was wondering if this is correct for this boat.It runs at 50 mph at 4300 rpm with a 19 pitch prop. I know this outdrive has been replaced but I don't know if its the right one.

 

[Bt Doctur]

Re: Right lower unit

gear ratios are in the upper on an Alpha, V8`s usually use the 1.50 ratio.
1.84 usually used with 200hp motors.
GEN II units have different lower unit ratios in addition to the uppers

 

[Don S]

Re: Right lower unit

If your speeds, and rpm are correct, and with that prop pitch, I would guess you have the correct gear ratio in the drive, no matter what the numbers say. If you actually had a 1.84 and a 19 prop you would have way high rpm, and much lower speed.

Someone probably replaced the gears in the drive and didn't change the numbers. If you have the Merc serial number of the outdrive itself, we might be able to find out what it went to originally.

 

[adray1]

Re: Right lower unit

Well the number on the outdrive is 9164005. I hope this helps. Thanks in advance Don S. I thought like BT Doctur in that the V8's had 1.50 outdrive and the 1.84 was for the V6's.

 

[Don S]

Re: Right lower unit

9164005 isn't a good serial number, might want to recheck it. Usually there is a letter in front of 6 numbers.

 

[adray1]

Re: Right lower unit

Try C914095. Sorry, this is hard to see. The ink wore off and the stamped is barley there.

 

[achris]

Re: Right lower unit

Try C914095. Sorry, this is hard to see. The ink wore off and the stamped is barley there.

And that number is for an electric thruster!! ..

Ok, the numbers in your original post are just wrong...

Here's what they look like....

But if I change the ratio to 1.50:1, then they look a whole lot better. So, if the speed is from a GPS and the tacho is reasonably accurate I would say that the ratio you have is indeed 1.50:1

Hope this helps....

Chris........

 

[adray1]

Re: Right lower unit

Thanks Chris. Sorry about those numbers, they are very hard to make out. Yes the speed is from a Garmen GPS but the tach is the boats original 25 year old VDO unit. I basicaly just held the boat at WOT while adjusting the trim and the best I could get was 50 MPH and 4300 RPM. I think I am going to be working with RCL Boats during the off season to get this Baja working right. Check out what these guys can do with sm blocks and alpha1 set ups. RCLBoats.com

 

[achris]

Re: Right lower unit

... I think I am going to be working with RCL Boats during the off season to get this Baja working right. Check out what these guys can do with sm blocks and alpha1 set ups. RCLBoats.com

Just remember that with a boat engine (no multi-ratio gearbox) that the optimum is a nice flat torque curve, it's torque that turns the prop, not horsepower. The worst thing to do is to build an engine that is very 'peaky', at low speeds it would be undriveable. Yes, you could get over 400hp from the SBC, but the cost is low end torque. And the Alpha style drive is good to about 300hp MAX!

Personally, unless you're doing offshore racing, or pulling a barefoot water ski team, 43 knots is plenty for ocean work. My boat does 43 knots with a little load and less than 1/2 tank of fuel, and it's a real handful at any speed over about 37 knots.

Anyways, good luck,

Chris......

 

[adray1]

Re: Right lower unit

I'am sorry, thats RLCBoats.com , tell me what you think.