Outdrive ratio??

[Joka]

I am in the process of getting my boat back on the water. My previous outdrive locked on me and I am in need of a rebuild. I have an '86 Sea Ray with a Merc 120 and the ratio is supposed to be 1.94:1 (i think).

Question:
I found an outdrive that is affordable at a ratio of 1.98:1 which is for the merc 140. Does the .04 really make a difference? I also have no idea which size prop would work for me if I have changed the ratio. Last question, I have always preferred a 4 blade prop; could that have been the reason for my lock up on the last drive?

Any help is welcome!

[Jango]

You will see absolutely No difference between a 1.94 and a 1.98 ratio - perhaps only 30 or 40 rpm at WOT. A 4 bladed prop will not cause a gearbox lookup. Lockup can only be caused by bearing, etc, failure do to inadequate lubrication or possibly incorrect shift linkage adiustment.

Jango

[Joka]

Thanks, that makes me feel much better. I did change the gear lube in the outdrive about 2 weeks prior to the lock up. I took the advice of my local boat parts sales man who had helped me in the past. He had told me there were two different types of lube, one i think was amber and the other yellow, warned me about using the wrong one. My father-in-law and I spent about an hour trying to decide which color the lube was, since it was brown it could have gone either way. I don't even remember which color we ended up using.

My next problem is I got my engine checked after I lost the outdrive and my mechanic told me the engine ran but only at 20% compression. So along with the drive replacement I need a rebuild. What is a normal rate for a merc 120 rebuild? I am a bit of a sucker since I am inexperienced at engine repair.

[Jango]

Not familar with costs for your engine rebuild. Since your "mechanic" is suggesting what amounts to at least a Re- Ring job, costs could be signicant.

If the Engine gets anywheres near normal WOT rpm (4000)while under load, it should be OK as is.
I would get more opinions on what if anything is required. A compression check should cost less than $50 and will tell you if the engine is truly running at "20%" compression.

[Joka]

Thanks Jango, will do! It seemed odd to me that my engine and outdrive went at the exact same time, so I will definitely get a second opinion.