80’s/90’s 50hp opinions?

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Viewing 10 posts - 11 through 20 (of 51 total)

  • johnyrude200


    Replies: 782
    Topics: 186
    #27425

    Good info to know. I just finished up, likely, the final run of my tritoon this season (yes, it’s Nov 20th, 51° out miraculously, and I waded into the water up to my knees to switch my prop). Not looking forward to pulling the docks out this afternoon. Once I thaw out on Monday, I’ll be able to get back on the blueboards 😯

    The ’78 35hp johnson was struggling to turn 4300RPM at WOT with a 10 x 13 prop. Switched to a 11 x 9, and voila! Hit 5500RPM and gained a few MPH. If I can find a 10 x 10, I might even take another trial run this year. I do have a 10.5 x 11 4-blade prop, not sure what that will do (opinions)?

    The motor is likely undersized for the boat, so I’m in the hunt for a 50hp motor, hence the genesis of this thread. Appreciate everyone weighing in on the pro’s/con’s. Now it’s just a matter of getting my hands on 2-3 of them so I can do the work on it myself as necessary!

    It goes about 15-17MPH now, but I want 20MPH+ to get around. That’s enough speed for me.


    jerry-ahrens

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 986
    Topics: 40
    #27434

    Dan, I was curious, did you have to grind the ridge off the mag plate on the 50 hp engines that you installed the CDI kit on? I have tried a couple of those [CDI] kits, and could not get them to fit. The CDI tech service guy said to grind the plate as needed to make it fit. I didn’t want to do that so I ordered a BRP pack and went that route.


    dan-in-tn

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 961
    Topics: 78
    #27435

    Jerry, I’m a little confused? The CDI kit I was referring to moves the pack out from under the flywheel (UFI) and puts it back on the side of the powerhead where it use to be in years prior on earlier models. CDI was making BRP ignition components for awhile so not sure why the BRP unit would be any different. No I have not had to make any alterations to the mag plate, but it has been some time since I have done one of these. CDI quality has been slipping, but I didn’t know they were making the components that still went under the flywheel! I would not go back that way. OMC had enough problems with that setup that I would go with the pack on the outside. Easy for me to say if you have invested your money the other way already. Sorry you didn’t know about the SNAFU!
    The retention bolts were just too small to hold the components on the mag plate. Even if the screws don’t loosen, they will fatigue and fail over time. I don’t believe there is enough meat there to enlarge the fastners (maybe metric), but that would be questionable at best.

    Dan in TN


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #27436

    Good info, never new someone made an actual kit to convert these engines back to conventional CD2 ignition. I’m thinking this kit must include a new mag plate though cuz I don’t think there is a provision for it on the UFI mag plate. Another fly in the ointment is that OMC changed the mag plate mounting style/hardware in the early 90s, I think concurrently with the return of CD2. So, I’m thinking this kit must be fairly pricey, but would love to see a picture if anybody has such a kit.


    chinewalker

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 459
    Topics: 15
    #27437
    quote johnyrude200:

    Good info to know. I just finished up, likely, the final run of my tritoon this season (yes, it’s Nov 20th, 51° out miraculously, and I waded into the water up to my knees to switch my prop). Not looking forward to pulling the docks out this afternoon. Once I thaw out on Monday, I’ll be able to get back on the blueboards 😯

    The ’78 35hp johnson was struggling to turn 4300RPM at WOT with a 10 x 13 prop. Switched to a 11 x 9, and voila! Hit 5500RPM and gained a few MPH. If I can find a 10 x 10, I might even take another trial run this year. I do have a 10.5 x 11 4-blade prop, not sure what that will do (opinions)?

    The motor is likely undersized for the boat, so I’m in the hunt for a 50hp motor, hence the genesis of this thread. Appreciate everyone weighing in on the pro’s/con’s. Now it’s just a matter of getting my hands on 2-3 of them so I can do the work on it myself as necessary!

    It goes about 15-17MPH now, but I want 20MPH+ to get around. That’s enough speed for me.

    You’re not going to get your 20mph without going to a bigger motor. 5500 is right where the revs will want to be. Going up in pitch will drop your revs and get the motor out of the sweet spot. Looking at your data, the 9P is the one you want. Lugging it with a higher pitch prop is akin to driving uphill, towing a trailer, in overdrive. The motor can build up heat, coke up the ring lands, and stick a ring into the cylinder wall – referred to as ring jacking.


    dan-in-tn

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 961
    Topics: 78
    #27438

    Im with Chinewalker. Since you are probably on the boat by yourself during these sea trials it’s only going to get heavier. 5500RPM is the about where you want to be. (5800 max for that motor, never 6100)

    Dan in TN


    johnyrude200


    Replies: 782
    Topics: 186
    #27439

    If memory serves correct, this same retrofit ignition kit is available for the UFI equipped 9.9/15hp motors too. Although I think you can just swap out components on the mag plate rather than replacing on those little motors. I could be wrong though!

    When I pulled the boat out earlier today, I clocked it at 17.8MPH but the water was like glass, and I was the only passenger. Looks like a bigger motor is in order. And it’s really a 30hp motor by today’s standards.

    Late 80’s 50hp motor…where are you? I’ll take an extra 20 ponies 🙂

    On a side note – I pulled the specs on an ’88 50hp motor from a service manual and they’re listed as 185lbs with electric/longshaft configuration. What I’m wondering is does this figure include weight from power trim/tilt.

    My 35hp motor weighs about 135lbs, then add the panther power trim, and that bumps the weight up to 160lbs (25lbs for the panther trim). So if there is only going to be a net gain of about 25-30lbs, seems like a no-brainer to swap motors. Probably almost no difference in terms of weight effects on the vessel.


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #27443

    the 185 pounds does not include the power trim/tilt unit. The 40-50hp will definitely perform better on the pontoon boat.


    dan-in-tn

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 961
    Topics: 78
    #27460

    We seem to have several threads mixed here, but Imguess that happens. The kit doesn’t change the mag plate. If you need one of those you have to buy it separate.
    The 50hp would be a better choice and if you could find the commercial unit with the larger 3cylinder/V-4 style gearcase it would be better still. The bigger blade area prop will work better on pontoon boats. Four blades are better than three for turns and cavitation. The 50hp can stand the full 6000rpm, but that is rarely what you need on a pontoon. WOT is not practical in most cases. Neither is trim, but nice for shallow water and tilting or setup. That’s why I like the ’89 model and up. Much better TNT unit.

    Dan in TN


    johnyrude200


    Replies: 782
    Topics: 186
    #27483

    What is a good normal range of compression values for these motors?

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