Mercruiser Gear reduction and prop

[peter8322]

Hello to the forum. I am new to this forum and trying to get some help with my new old boat. I purchased a 1999 Chaparral 200LE with what I believe is a 5.0 L alpha 1 gen2 mercruiser drive. I found the following serial number on the transom OL556903 and the out drive states 1-52R with the following serial number DL467256. What has me confused is I cannot find this gear ratio on any of the websites for Mercruiser and my serial numbers don't seem to work either. Lastly the prop on my boat is a 23 pitch ss prop. Is this appropriate for this boat. Any help understanding what I have would be appreciated. Thanks

 

[Leardriver]

Knowing your gear ratio is great theory, seeing how many RPM's your motor will pull with a full fuel tank and a normal operating load is better for reality. Have you taken it out?

That number on the outdrive might be a 1.52 ratio, right hand rotation. I don't know Alphas much.

 

[peter8322]

Have not had it out yet. But looking forward to. Needed a lot of cleanup.

 

[peter8322]

Just very weird that says 1-52R on out drive and gives serial number but cannot find anything on it on the Internet.

 

[Bt Doctur]

1.52 is usually on the 5.7 260Hp motor. A 5,0 will usually run the 1.65 or 1.84 ratios being only 200 or 220 hp
You may have to remove the drive and turn the inputshaft by hand to determine what ratio you actually have

 

[Scott06]

I would think even with a 1.62 ratio 23” pitch would be too much.
you sure the 1.52R is nit actually a 1.62 that would make sense with the ratios which were 1.47, 1.62, 1.81, and 1.98

verify what the ratio is and try the boat out see what you get for wot rpm before playing with props. Really depends on how you use your boat. If you run loaded down with people or do a lot of watersports you may want to drop pitch

Mercruiser Alpha Generation 1 & Mercruiser Alpha Generation 2 Sterndrive Gear Ratios Determination | PerfProTech.com

Large selection of quality mercruiser parts, marine engines, marine parts, boats parts and accessories, such as Mercuiser engines, exhaust, motors, and other boating supplies and accessories. Find affordable parts for leading brands including Volvo marine parts, Mercury marine parts, Quicksilver...

www.perfprotech.com

 

[peter8322]

Hello Scott06. You nailed it I did read the decal incorrectly and it was a 1.62R not 1.52. thanks for the advice to recheck. Now that I have that figured out what is thoughts on prop size? I am new to props and prop choices. Higher pitch equals less power out of hole but more top speed at lower rpms?

 

[Scott06]

Hello Scott06. You nailed it I did read the decal incorrectly and it was a 1.62R not 1.52. thanks for the advice to recheck. Now that I have that figured out what is thoughts on prop size? I am new to props and prop choices. Higher pitch equals less power out of hole but more top speed at lower rpms?

in a nutshell Yes higher pitch will lower wot rpms, lower will increase holeshot and increase wot rpms.
as mentioned above try the boat out and see where your wot rpm lands before doing anything. depending on if your engine is carbed (220 hp) or mpi (260 hp) It will have a range of 4400-4800 rpm ( carb) or 4600-5000 for mpi. you want the prop such that with a typical load you can get in the correct rpm range, preferably towards the top.
this doesn’t mean you have to run it at wot all the time, just that if it can hit that rpm range the pitch is correct for the boat and how it is set up load wise. A lot of people go up in pitch thinking it will make the boat faster, but that only works if the engine has enough power to swing the extra pitch. This ends up lugging the engine and Likely leading to detonation.

start with the basics make sure the engine is in good shape in terms of fuel and igntion systems, do some basic checks like the bellows, change the oil and gear lube if not done. If you don’t know when the water pump impeller was last done it’s a good time to do it.

 

[peter8322]

Yep good points. I am draining oil right now and planning on removing drive and changing pump before season starts.
Thanks for input. Any other mtc you would suggest while have the drive removed.

 

[Grub54891]

Where you at? If freeing temps you will need to winterize so the block doesn't get destroyed over winter.

 

[peter8322]

Yep boat is winterized last week. I am in Ohio with teens temps right now

 

[Bt Doctur]

if it was done correctly ,your safe. If done with the AF thru the muffs without draining everything first, your st risk of freeze damage

 

[Scott06]

Yep good points. I am draining oil right now and planning on removing drive and changing pump before season starts.
Thanks for input. Any other mtc you would suggest while have the drive removed.

While it is removed check the gimbal bearing and u joints, if there is no water intrusion into the bellows are likely ok. While drive is off pressure test it to assess seal integrity.
check out the igntion components see what the plugs look like

 

[peter8322]

I have heard of pressure test but do not know how to do this. Will have to find a procedure. Good reminder on gimbal and joints.

 

[Scott06]

In the top of the mercruiser section there are stickies in there are links to how to build a tester and do the test. Otherwise google it you find a chit load of stuff on YouTube

Basically empty the lube from drive rig up hoses fittings and valves to put 15 psi compressed air.

I used a plumbing fitting made for pressure testing had a schrader valve and gauge some fittings hose and the fitting off an old gear lube pump to screw into outdrive

I have heard of pressure test but do not know how to do this. Will have to find a procedure. Good reminder on gimbal and joints.