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Thread: Urgent - please help!

  1. #1
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    Default Urgent - please help!

    Hi all - as per the title I'm in a bit of a situation.. I went and picked up a '50hp' yamaha 3 cylinder at the weekend. the seriel / model number tag on the transom bracket was missing which did worry me, although the seller did provide paperwork for the security stickers (they leave a mark which can be picked up by law enforcemnt if removed) so this paperwork made me happy enough it wasnt a stolen engine - plus the serial number still reamains on the 'Plug' in the block.

    Anyway, cut a long story short, I got the motor home and I began looking around it now I had plenty of time and I noticed the cowl was a slightly different shade of blue (as used on 90's motors) to the rest of the outboard... I had then suddenly realised.. to check - I looked at the carbs and they are marked: 6H400VK07 (09 and 08 on the other 2 rather than 07) which I think is a part number telling me its a 40hp set of carbs??

    I also looked for a number on the exhaust manifold, which also happens to begin with 6H4, which again I think means its for a 40??

    So I am thinking I have just brought a 40hp yamaha with the cowl of a 50hp.. What makes it difficult is that I can ('Least I think?) only go by the cowling colours / decals to guess a year - due to there being a revision in the water pump in 95' I figured it must be a 1994 model.. although how can I tell what the heck I've got now??



    I have contacted the seller today - and he seems very apologetic and has said he will work with me to find out what the engine is and if needed - he would send me the parts needed to make it a 50 as advertised.. trouble is I'm not 100% sure what parts are different? the 50hp carbs (as far as I'm aware) are marked with a number starting 6H5 and I assume that the exhaust manifold should also start with 6H5 on a 50 and 6H4 on a 40 (this is going off of the parts lookup for yamaha outboards)

    So in summary, can anyone confrirm wherther this is a 40hp with a 50 cowling or not and if so..Is there anything else I would need to convert this engine to a genuine 50hp spec?


    Thanks in advance (the leg has been badly resparayed at some point, although the upper section looks to be original - though it is an ever so slightly different shade to the cowling) - I have attached some pictures of the engine just case it helps...

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  2. #2
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    post model number here and then someone will tell you what the engine is.

    sounds like you have a bitsa motor.
    Thanks Ron Hill thanked for this post
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    thats the main issue, the label with the model number is missing unfortunatly - I'm fairly certain it's just a 40 with a 50hp cowling - would it help at all if I posted some picis with the cowling removed?

    as long as I can be certain the carbs etc are from a 40, I will just convert it to a 50, as long as I can be certain what the exact differences are

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    what is the number of the disc on the block, or any numbers on the block ?
    check numbers on things like starter and electrics, you might be able to get a date of manufacture by those.

    must be plenty of people on here that will know those motors inside out.

    .

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    I believe the main difference between the 40 and 50 are the exhaust tuner and carbs. So look for 6H5 vs. 6H4 on those parts (tuner is hard to get to). I just looked at 1993 Pro50 carbs and they are stamped 6H5 on the side of the main carb body.

    That is a short shaft. And over here that lower gearcase was used pre-1995. Not sure but Timing adjustments might also be different for 40 vs. 50. edit: also not sure but NGK Spark plugs might be different 40 vs. 50..

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    Why not just contact Yamaha with the serial number and ask them...?????

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    Quote Originally Posted by hydrospeed77 View Post
    I believe the main difference between the 40 and 50 are the exhaust tuner and carbs. So look for 6H5 vs. 6H4 on those parts (tuner is hard to get to). I just looked at 1993 Pro50 carbs and they are stamped 6H5 on the side of the main carb body.

    That is a short shaft. And over here that lower gearcase was used pre-1995. Not sure but Timing adjustments might also be different for 40 vs. 50. edit: also not sure but NGK Spark plugs might be different 40 vs. 50..
    thanks for the reply - good points on the timing and plugs - hadnt thought of that. what was different about the gearbox - I'd know the water pump changes slighty 95 on...

    cheers

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    Quote Originally Posted by 25XS View Post
    Why not just contact Yamaha with the serial number and ask them...?????
    I wasnt aware they could look them up - I'll try to get in touch with a dealer soon

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    Some pictures under the cowling - I think the carbs look like the ones used before the 90's?

    ughh...

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  10. #10
    Team Member 88workcar's Avatar
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    A 40 will have more low end than a 50, a 50 will run slightly more top end. You already see the carbs, so.....The only way to know for sure is to see the tuner. A 40 has a round hole at the top and a 50 has a square. You can pull the power head and look or pull the lower unit and try to see or bore scope it. At the end of the day....... on stock engines, most folks will never notice a difference from a 40 to a 50. Stop sweating all that and go enjoy your motor.
    Helping folks out around the globe.

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