I just got a 1980 Renken w/OMC stringer

[Justin_S987]

Hello, I am new to here and new to boats as a whole but boating is something I have toyed with trying one day. So, out of the blue I came into possession of a free, but oddly, ok shape 1980 Renken... bowrider?? ...as close as I can tell but it has a solid deck on the bow. With an OMC 120 stringer outdrive. Story goes, a 69yo man was nearly finished rebuilding it in 2022ish and was holding off on reassembling it until he got a new set of ball gears. He finally just decided he was too old to work on it alone anymore and gave it to a couple I know until it sat in their yard 2 years and they gave it to me for free so they can move.

I have had this boat 2 weeks and gone down many rabbit hole researching it. I have since discovered that OMC anything is just a teensy bit outdated and complicated, but sounds doable and just up my alley and skillset. I plan to just take this boat out on rivers and lakes in the area and not push it too much.

From what I was told, the binder with the manual, along with handwritten notes, the boat is from Ohio, only ever ran in freshwater on the great lakes and some in SC. The boat has a new wood floor and transom that are coated in a black fiber coating and new carpet. It has a brand new full cabin canopy and everything attached to the hull is solid.

The engine is weathered but runs really well, has new coolant hoses, new fuel tank, fuel lines, filler tube and blower tube. No leaks or smoke. The engine didn't start at first and I traced it to the breaker contacts on the distributor being out of adjustment but it runs great afyer adjustment. So far I have only run it 2 minutes at a time and watched it with a temp gun since I can't run water through it yet.

The outdrive was already detached and it was easy to see that the hull side drive gear had severly worn out teeth. It appears the og owner had started to unwire some things at the dash like lights and radio but everything needed to start, run and steer is in working order.

Sorry to ramble on but...so far I have inspected the hull, transom, transom boot and floor for cracks and rot, I have found none but I also have not fully removed the carpet, so all I know for sure is the transom seems good there. I tidied up the engine and tested it. I found a new set of ball gears and seals on ebay and installed them and this coming week I plan to reattach the outdrive and test it.

At the moment I am curious about a few things. I found that engine had no or little oil in so I put 2 quarts in before testing (SAE 30), and the new coolant hoses dripped antifreeze before I tightened them up, so I assume that is winterizing and needs removed?

Next, both the ball gear housings had thick brown oil behind them. Is this seperate from the gearcase or will it get changed with a gear oil change? I bought 4qt of SAE 90 that says it is a direct substitue for 80w90 to change it with.

Finally, I am ordering marine grease for the drive hinges, tilt gear and steering gear but do I or should I apply grease to the ball gears as well?

 

[Scott Danforth]

Welcome aboard

Free boats are often the most expensive

OMC is obsolete, not outdated. The 1980 hydro-mechanical drive was a short-lived 3-year only problem child (78-80) quickly replaced with the full mechanical shift

There are 3 separate gear boxes, not including the tilt clutch gearbox

Put in a new raw water pump. And inspect the 3-piece vertical driveshaft. They are failure prone. Check the internal splines

Don't forget to service the tilt clutch oil

The description of the floor is a red flag

 

[Justin_S987]

I'm wondering about the floor too, it has some barely noticeable give just in front of the engine area but solid everywhere else. New or not, Ill probably end up pulling the carpet to inspect it. The roof was not fully zipped at the corners in a few places and dripped to the inside but it did have a boat cover for most of that time until they say it ripped and they put the roof up. Worse case, I take the old out and use it as a template for a new floor.

In the binder I received with it, there are receipts for several water pump parts and labor, including the drive change impeller, impeller key, pump shaft seal and a water pump kit. Now that I look again, one receipt from a marina says "Found internal issues with knuckle, leave drive off". I'm not sure what the knuckle is. I am assuming the water pump was rebuilt in 2018 at the time of these receipts. But Ill take the housing apart to check it if I have to.

I had forgotten about the tilt clutch, I know the electric motor works and turns the tilt gear on the outside but Ill check it out too. Thanks.

 

[Scott Danforth]

Usually when the floor rots the stringers and transom rotted decades earlier

Check to see if the boat simply had a "deck-over"

Deck over defined: Slap plywood over the rotten deck and sell it asap (boating equivalent to 5# of bondo filling in rust at a used car lot)

 

[Bondo]

but it runs great afyer adjustment. So far I have only run it 2 minutes at a time and watched it with a temp gun since I can't run water through it yet.

Ayuh,..... Welcome Aboard,...... 2 minutes run time without water flow is plenty of time to smoke the rubber raw water pump impeller,.....
Never, Ever, run a raw water pump, without water flow,....

 

[Scott Danforth]

Not to mention without cooling water, you burned the rubber exhaust bits

 

[Justin_S987]

Uhhh, hmmm. According to the OMC manual I have, the water pump is inside the drive unit right? Because it's not attached at the moment. the engine was just running the shaft with no load. I am aware it needs water to cool so I was trying to be cautious and just make sure the engine started and then wait until I reattached the drive unit to test anything further.

Yeah, I'm kinda nervous about the floor myself, Ill probably pull the carpet and look for evidence of water damage and maybe pull up the wood to check sometime soon.

 

[matt167]

The impeller is in the drive. However there are rubber parts in the exhaust you may have toasted

 

[Scott Danforth]

Take the garden hose and connect it to the thermostat housing if you want to run it. However you toasted the rubber in the exhaust

 

[Justin_S987]

Take the garden hose and connect it to the thermostat housing if you want to run it. However you toasted the rubber in the exhaust

Oof, ok. Guess Ill inspect everything again as I go. It will be easier to find anything I need and replace it before I put the drive back in the way. I only thought it was safe to run because I was told you can do it for like 5 minutes at a time. I ran like that 3 times to be sure it worked on its own and shut off the engine when ever it got close to 100°.

 

[Scott Danforth]

. I only thought it was safe to run because I was told you can do it for like 5 minutes at a time. I ran like that 3 times to be sure it worked on its own and shut off the engine when ever it got close to 100°.

You were told wrong

It didn't show more than 100 because there is no water in the block

With cooling water, your exhaust temp is 200f

Without cooling water, the exhaust temp is 1100f

 

[Justin_S987]

That makes sense. I hope I didn't do any major damage to the engine. I was trying to be careful to the best of my knowledge.

 

[Justin_S987]

I didn't want to start a new thread for a quick question so I am bumping this post.

What would a pump with the impeller in backwards act like? Because I got ahold of the original owner and he said he had been waiting for an opportunity to replace the pump because it wasn't pulling water and when I pulled it apart myself, the impeller was clearly reverse of the OMC manual instructions. Manual says ccw and his was installed cw. I'm thinking the impeller being backwards would create little or no pressure and just stir up water if its anuthing like the CNC impeller coolant pumps at work, but it seems weird it would go unnoticed for so long if it wasn't pumping water. Should I be looking for other things that would stop it from pumping water?

Photo is how it looked when I took it apart cw. I replaced all the pump components with new ones minus the shaft, according to the OMC manual which is ccw.

 

[Scott Danforth]

you can put the blades any way you like. they straighten themselves out when the motor turns.

 

[kenny nunez]

Be sure to seal both sides of the stainless plate and the 4 bolts where they contact the stainless cover with #2 Permatex. From the picture of the water pump it should have worked. Do as SD said, run the engine with a hose connected to the thermostat hosing before installing the drive. This way you will be able to watch and feel the exhaust manifolds and risers if one or both are blocked. This also will prove out the thermostat‘s operation.
Turn the helm both ways then split it to center the steering gear, on the drive turn the steering gear to center the distance between the rear of trunnion ears and the front of the exhaust housing. This way your steering will go full in both directions. Use grease on everything, bolts, “O” rings and trunnion side cover mating surfaces.

 

[Justin_S987]

Yeah, I need to buy some permatex to seal it all. I am also wanting to replace the upper and middle shafts for the pump and gearcase but the lower gearcase looks really good from above but I also haven't disassembled it.

The upper and pump shafts obviously need replaced soon so I am going to order the parts now. I have found them on ebay but I would like to find the part numbers to verify what I have is correct before I order anything. I can find the shafts, " NIB OMC Stringer Water Pump Shaft w/Short Low Profile 1978-1985, 18-2185, 909753" and "OMC 981220, 0981220 Stringer Sterndrive Upper Driveshaft Shaft & Sleeve" that seem right. I have also found a complete "new old stock" complete upper gearcase assembly which would be nice instead of rebuilding my gearcase bc the cost will nearly be the same either way, but I would like to find the part numbers to verify they are correct. I didn't see them in my manual.

 

[Justin_S987]

Update, the Ebay seller sent me to a site with all of outdrives parts numbers by brand so I have found them.

Here is the link in case it helps anyone else.

https://www.marineengine.com/parts/omc-parts/omc-boat-parts.php?year=1980&hp=120&model=990242C&manufacturer=OMC+stern+drive&section=Upper+Gearcase+Group+120%2C140+Models+Stern+Drive

 

[kenny nunez]

You need a Genuine OMC service manual for how to replace the pinion shaft and the seals.

 

[Justin_S987]

You need a Genuine OMC service manual for how to replace the pinion shaft and the seals.

Yep, original owner was very meticulous and gave us a an OMC Repair Manual along with all of his documentation and personal notes, it's been very helpful so far. Just hard to find part numbers for everything in the diagrams sometimes.