Year of Manufacture Mariner 75hp

"Hi to everyone on the board.

"Hi to everyone on the board. This is my first post. I recently purchased a speedboat with a 4 cyl 75hp outboard. I've searched all over for the serial on starboard side, but there are no plates anywhere. There seems to be a sticker on the front behind the housing cover, but its completely obliterated. I'm hoping that if I post a picture, someone may be able to give me an idea of age, and also petrol/oil ratio. Much appreciated. Paul "

"You may find a sticker on the

"You may find a sticker on the exhaust housing (leg). If you stand behind the motor, swing it all the way over to your left, then look on the right side right near the upper transom mount.

If nothing there, you have another chance. Take off the hood, and again, standing behind the motor, look on the water jacket of the cylinders on your right hand side.

You are looking for a welsh plug - that's a small silver disk about the size of a quarter. It will contain the serial number for your motor.

See pic (this is a little evinrude, but the Merc's are identical - it will give you an idea of what/where you are looking). Sometimes you will find it on the water jacket smack between the two cylinders on that side.

If you find it, post the number and can help you out...

"

"The one positive note I can a

"The one positive note I can add is, Mariner 75 horse models were built between 1986 and 1996 and were North American models - so you will not have an orphaned motor built for Merc by Yamaha..."

"Hi Graham,

Thanks very muc

"Hi Graham,

Thanks very much for your reply, I couldn't find anything like in your pic, but thats just probably me being dumb....lol.

What I did find was on the transom bracket a number stamped 3400-8715, but this was on left side looking at the engine from the back.

On the actual cylinder itself beside the plugs, I found 817-8337, pretty much where you explained, but this was on the body of the block rather than on a silver disc as you explained.

thanks again

regards

Paul"

"Having realised none of the a

"Having realised none of the above are serial numbers, I'm going to post some more pics, so that someone can hopefully help me find this elusive serial???
thanks

Paul"

"You are making this difficult

"You are making this difficult

We will have to keep digging.

Looking at your motor though - particularly based on the hood design, I would suspect that it is at least a 1990 (and my guess would be an early 90's) but we can keep investigating.

I don't think that it is a 95 or newer (but can't be sure at this point).

The one positive thing though, is that they made these motors in a series and all parts in that class are totally interchangeable. So for example if it was built anytime between 86 and 94 it is essentially the "same" engine...."

"Paul, could you confirm that

"Paul, could you confirm that this is a 4 cylinder model. I overlooked that at first and just assumed it was a 3 cyl, but I noticed the 4th plug wire/coil.

If it is a 4 cyl, then I am fairly positive that this is a 1989...."

"Hi Graham,

Thanks for bear

"Hi Graham,

Thanks for bearing with me on this.Yes, its definately a 4cyl as stated in my first post. It would be great to know that it is an '89, its just that I can't find any reference on it anywhere Graham.I so tried to find the silver disc, but it doesn't seem apparent, can you see it anywhere on my pics.............I know they are small though...sorry!!.

regards

Paul"

"The welsh plug looks to be bu

"The welsh plug looks to be burried pretty good on your motor - it will be on the right hand side waterjacket (if you are behind the motor).

However, the hood design combined with the fact that it's a 4 cyl, strongly indicates that it's an 89.

Merc streamlined the hood design for all the 1990 models (hence my first guess), but after noticing you had a 4 cylinder (which they last built in 89) that kinda narrowed the possibilities.

It still could be an 87 or 88 maybe, they were technically identical. For the purpose of parts or service it really doesn't matter what year you call it as long as you have it narrowed to a model class.

Your serial number will be 7 digits looking something like 9312574 etc...."

"Thanks Once again Graham. So

"Thanks Once again Graham. So we've possibly narrowed it down to an '89, which is a start isn't it.Thanks for your patience and knowledge, although I would love to find a serial number somewhere....lol

regards

Paul"

"Yes, I would suspect that the

"Yes, I would suspect that the welsh plug containing the serial number is behind the electrical box (far right pic you have posted).

The usual location is on that side, water jacket, near the rear of the motor - so if you get ambitious you could undo the few screws holding that to the powerhead, just move it out a bit and have a look..."