Testing used gearcase procedure

[Campster]

I am going to look at a replacement gearcase for my 40hp omc early to mid 90s. Its identical to my current, just different color. What can I do to test whether it functions properly as it is off the off powerhead and midsection. Outside of inspecting external condition, checking oil for metal, pressure testing, can I check whether it shifts properly? For example, can I pull straight up on shift rod while rotating drive shaft by hand to engage gears and see if prop rotates, etc? What would be suggested procedure to increase odds I'm not buying a paperweight? Any advice from the experts would be appreciated. Thanks.

 

[Tim Frank]

I'd think your greater risk is buying something that is non-interchangeable.
The fact that you are describing your O/B as a

early to mid 90s

leaves a pretty large range. How are you ensuring that you have an exact match?

there have been many posts in here over the years like ~

I bought a used L/U for my motor. It bolted on fine but when I put it in Forward it goes in reverse.Put it in reverse and it goes forward.

....etc.

 

[metriccrescentwrench]

I bought a used L/U for my motor. It bolted on fine but when I put it in Forward it goes in reverse.Put it in reverse and it goes forward.[/I].

Well, that particular issue shouldn't apply here as that was with gearcases from the late 70's (I got my education on those when an ebay seller tried passing off a '70's gearcase as a 1988 model) . But yes, your point of ensuring compatibility is a good one.

Campster.... yes, you can pull the shift rod up to shift into forward (might need to turn the driveshaft as you shift), rotate the driveshaft clockwise (as viewed from above) and the prop shaft should turn clockwise (as viewed from behind) and likewise push the shift rod down to go into reverse. After it's shifted the driveshaft should turn smoothly (but you'll probably have some resistance from the water pump impeller). If possible drain a bit of oil and check for water.

After you buy it plan on servicing the water pump, no telling how long it's been.

 

[Campster]

Thanks guys for the advice...on parts interchange..i checked this website for my model number and the donor model number and the recommended replacement part # is the same for a complete gearcase unit, so I dont think there will be a problem with fit. I did the recommended check on shifting gears and was able to check forward before thunder & lightening & hail cut the inspection short...no metal filings in gearcase oil, it wasnt burnt, but slight evidence of milkiness. exterior of case was in very good condition...Bought it for $50 bucks, will see if it works in a few days.

The gearcase oil used was the standard honeycolor...can this be drained and replaced with the blueish stuff (which is what I use in my larger merc) or do i need to stick with the kind that is already in the case (my merc high perf lube says not to mix with basic)? Thanks again.

 

[dazk14]

double post. Keep getting error messages from iboats, even when it gets posted. When I refresh page is when I can see that the post made it.

 

[dazk14]

Drain out your own oil, and use whatever oil you prefer - no problems. The Merc stuff is good, the BRP hi performance(pricey) is very good and holds moisture in suspension better than any others I've seen - maybe the preferred choice in your case.

Usually the shift shaft seal goes 1st. small inexpensive o-ring, but a pressure test is ideal.

 

[Campster]

Crescent and daz, thanks much for the replies. Checked pressure and it seems to hold. Put in 16lbs as per manual, 20 min later between 15 and 16lbs. Not sure if small leak is in my cobbled tester, or in case, but figured good enough till the fall. Serviced water pump with kit. Filled case with new oil, Fiddled a bit getting shift shaft adjusted correctly to the spec, Bolted her up, and she tested fine in barrel! Will see how she does on water in few days. crescent...see u have a checkmate...that is my other boat!(the 40hp is for an old tin starcraft i redid)... a 1983 enticer with a 115hp...been in the family since 84, still in decent shape. Btw,pictures in your project link were shown as moved..will look for it with search to see your machine! I really like that era 'mate, fine boat. Frankly I am partial to the open bow all things considered.