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  1. #1
    Join Date
    Jul 2006
    Location
    Medford, MA, USA
    Posts
    6

    Default "Hi All! Any help would be gre

    "Hi All! Any help would be greatly appreciated. I have a 1986 70 HP Johnson (J70TLCDC)I am running it on a 20FT JC Pontoon of the same year. I have just recently purchased the motor used from a fairly reputable marine salvage company in NH. I have already installed it on the boat with an OMC tach provided by the seller. Problem is I have gotten 2 different answers on Tach pulse setting and WOT range from the seller and one of the local marinas. The local johnson dealer will not talk to you unless you are buying something so they are useless. Anyway Seller told me to set the tach at 3 and the marina (who sells Mercury) said it should be at 4. Both seem wrong. On 3 I cannot get above 3900 RPM's with a 14X11 prop. On 4 it goes over 7000. On 6 I am at about 6300. After doing much reading around all the boards it seems 6 would be the correct setting. By the way in order my choices are 2, 3, 4, 6 and 5. When it come to WOT I was told by seller to shoot for 5200 and by Marina 6000. Seloc Manual seems to have a misprint for this in the manual I purchased as well. I do not want to ruin the motor so I want to find the proper setting and range. Motor is used but runs real strong. No problems other than this. Thanks for any help you can provide I want to enjoy the water but cringe that I may kill one motor and have to buy another."

  2. #2
    Join Date
    Apr 2006
    Location
    , Langkawi, Malaysia
    Posts
    5,750

    Default "The tach setting depends on n

    "The tach setting depends on number of charge coils under the fly wheel, and on Yours I think to remember 6. As for WOT 5500-6000. Do not overload, too low rpm, on this engine or You may suffer dammage on cyl 2. The same goes for cooling, so be sure your waterpump, impeller and pressure-valve works. If impeller and thermostat have not been serviced/changed/checked recently have them changed/checked!"

  3. #3
    Join Date
    Jul 2006
    Location
    Medford, MA, USA
    Posts
    6

    Default Thanks Morten! I was thinking

    Thanks Morten!
    I was thinking along the same lines as far as WOT. I found it in the manual but it was backwards. I spoke with the Johnson guy at Seloc who confirmed it is 5000-6000. I thought 6 too but I am going to get a second tach with instructions this week before heading to the boat this weekend to double check RPM's. If the 6 reading is right I may have to go down to a 13 pitch prop. Once I get the RPM's correct and seem to have things under control I am going to send it to the marina I trust for a second inspection to be safe although I think it is fine. Thanks for the feedback I will repost with results after the weekend.

  4. #4
    Join Date
    Apr 2006
    Location
    , Langkawi, Malaysia
    Posts
    5,750

    Default "You have the maximum power at

    "You have the maximum power at 5500, but with tolerances 5 - 6000 is allowed. However as I mentioned try to go for just above 5500. 13" pitch sounds reasonable. The general change in rpm pr 1" pitch change is 200, but may vary a bit from type of prop, cupping, blade area etc and not to forget where You are in the power curve of the engine."

  5. #5
    Join Date
    Jul 2006
    Location
    Medford, MA, USA
    Posts
    6

    Default Just wanted to post an update.

    Just wanted to post an update. Setting for Tach is 6. I bought a new tach as well with instructions to make sure it was correct. I am running 6100 with a 14X11 prop so I think I need to go to a 14X13. Should bring me to about 5700. I used GPS and got a speed of 20.5 at 5800. So i am think with a 13 pitch maybe I will eek out a mile or two an hour at the same rpms.

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