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Yamaha/Mariner prop fitment

H. I. McDunnough

H. I. McDunnough

Regular Contributor
I recently spun the prop on my 1979 Mariner 40B outboard, and am currently shopping for a new one. It was a Black Max (extra surface area) 10 1/2 x 13P. It worked perfectly for my rig ; I got 29 mph at a max rpm of 5500. My spare is a Vengeance 10 1/8 x 14P, which I am currently using. It runs at 26mph at a max rpm of 5000. I am currently looking at a Yamaha 10 3/8 x 13P. I know my motor is a Yamaha and had always wondered if it should have a Yamaha prop for a few reasons. First, I have always had trouble torquing Mercury props on. The castle nut's machined surface never comes in contact with the prop. Instead, the tapered sides grind into the prop. Second, the castle nut turns onto the shaft so far that there is barely enough nut left to contact the cotter pin. I also noticed that the pictures in the service manual show a white prop, but it has recommendations for Mercury prop numbers. I'm thinking that Mercury just wanted to sell their props before they actually changed to a Mercury prop shaft. Does anyone know if this is really the case, and if I can or should use a Yamaha prop? Thanks.
 
I have used a Merc prop on an 1981 Yamaha 75, borrowed off my '69 Merc800, so if it fits and as your Mariner 40B is a Yamaha, then it will work.
 
I used the Yamaha thrust washer on the inside and a spacer on the outside, it left the castle nut too far out to get the cotter pin in so I used a locking nut. This is the Yamaha nuts and washers that were there and used by me, except for the castle nut, originally. So I'm thinking you have Yamaha gear. That prop is a rehubbed Mercury prop that I was practicing on and messed up but still works. IMG_20230610_210108329_MFNR.jpg
 
On the Yamaha is the three blade prop from my Merc900 but plenty of room for the castle nut to seat, ignore the crappy stand, it was thrown together from scrap I had lying around.Jeez I'm having a bit of bother working in this new layout.IMG_20230610_205418075_MFNR.jpg
 
You’re just the guy I wanted to talk to! I wanted to do a hub too. I have access to a press. I found some hubs on eBay, but can’t find anything to reference what fits what. The whole thing seems like an industry secret. It can’t be that hard; the guys at the prop shop don’t seem like rocket scientists to me. Have you done one successfully?
P.S.: Your motor stand looks great to me. Put that scrap to work!
 
I got my hubs here, https://www.hmshubs.com/products/ ,and I watched a video on youtube. Not this one, this is newer than the one I watched, can't find the other.
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I had a bit of pipe as a guide with a piece of s/s exhaust pipe adapter cut to cover the hub cavity pushed down inside. Put the hub into hot water ,shy of boiling,148f if my memory server me right, for five minutes, lubricated with plenty of dish soap mixed with alcohol @ 1:1 and chatted to all deities who would listen. I had a link but it has gotten corrupted by whoever the hell laughingboy is.
I have one that worked, different style of hub. This one slipped off the pile of spacers I had placed under to keep the diffuser ring off the press, more haste less speed:(
Before anyone jumps on me about leaving it to the professionals, where I live these are in short supply and when I did this there were none that I knew of. Today it would be cheaper to buy a new prop than buy, ship and pay excise duty on the hubs. Ye Yanks don't know how good you've got it:D. Duty @ 25% and USPS international rates are crazy, which the duty has to be paid on as well.
 
I'm writing this for anyone who comes across this searching for the same answers. What I learned is, either my Japanese Mariner prop shaft is identical to a Yamaha F40 or they are completely compatible. In order to use a Yamaha prop on a Mariner, as Haventaclue stated, you need the proper hardware (photo 2). I also found that all that was needed for a proper fit with a mercury prop was to add a washer, contrary to the instructions that come with it (photo 3). I like the fit of the Yamaha prop better. The thrust washer fits neatly inside of the bearing carrier, with what looks like a o-ring seat, flush with outer edge. I think it might be there to collect fishing line. Once the spacer and washer were on , the castle nut lined up perfectly with the hole. I did use a thicker cotter pin than was supplied, just to keep it from rattling around (photo 1). IMG_1510.jpgIMG_1515.jpgIMG_1517.jpg
 
That is a nice clean looking Yamaha, sorry, Mariner:D
Merc Marine collaborated with Yamaha from mid '70s through to mid '90s. So what Yamaha did was use their older models, painted them Mariner grey and badged them as such. They were for sale mainly in Asia and Europe.
Hey Graham Lamb I was paying attention in class:). Graham is the guru on these Yamaha Mariners.
 
It’s okay, you can call it a Yamaha. Over the years I’ve put more Yamaha parts on it than Mariner. Yeah, Graham helped me raise this one from the dead. He must be letting you take the easy questions now.😜 I had it out on the water. I’m back up to max rpms, and even got a little over 29 mph, well 29.1.😊
 
Great stuff .Glad to hear it's running well. I missed out on one of these a few years ago. My wee pet, RIP, reckoned if I got another boat, she was getting another dog, three boats and three dogs were more than enough about the house:LOL:.
 
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