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Posts: 1023
| I am thinking of moving my 70 hp 4 stroke johnson up 1 hole on my crestliner but need advice and opinions please. Right now, I am getting almost 5200 rpms and only 31 mph on my crestliner 1650. Full throttle operating rpms are supposed to be 5200 -5800 rpms and I think I should be hitiing 35 mph with this set-up.
I don't know my prop pitch... but I can tell you that my tell-tale or water pump pee-hole bobs under water at rest so the engine sits quite low. My gut tells me that I should move the motor up from its position (now at second lowest hole setting).
Will this increase my rpms and top speed. Right now I get a great hole shot and the engine runs well. Just wondering if this will help?
Also, can I do this with a friend (auto mechanic) seeing as the motor weighs over 300 lbs!!! I don't want to pay 100$ just to move my motor up at the marina and then pay 100$ to drop it down again if it does not work!!!
I could change props I suppose too, but the tell-tale in the water seems to be screaming "move me higher!".
Thanks for your help everyone!!!!! | |
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| Great info here; http://www.veradoclub.com/smf/index.php?topic=137.0
//Stefan | |
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Posts: 1023
| Thanks Stefan. That was a great site - pictures and everything. Can't wait to try it this spring. Does anyone know if raising the engine is a dealer only operation - for a 350 lb motor??? | |
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Posts: 3479
Location: Elk River, Minnesota | Nope...you can do it yourself on any flat hard surface.
Basically, the trailer jack (given you have one) does the work for you.
Step 1: Attatch tie downs from the boat to the trailer.
Step 2: Lower trailer tongue jack down as far as it can go.
Step 3: put blocks under the skeg of the motor and trim the motor out until the skeg base is flat on the blocks.
Step 4: Remove the upper mounting bolts from the transom
Step 5: Loosen the lower mounting bolts, so that the motor mount can slide. It may take a little grunt-work to get the motor mount loose since silicone is used and will act like glue.
Step 6: Slowly raise the tongue jack...this will force the stern of the boat down, and when the motor is free from the transom, it will slide easily.
Step 7: Continue to raise the jack until your upper mounting bolts line up where you want them with the motor.
Step 8: Re-insert upper mounting bolts. Be sure to put a ring of silicone around the big washer on the front side of the transom, then around the bolt after you push it through, before installing the nut. Tighten nut (and lock nut if a second one was supplied)
Step 9: Add some silicone around lower mounting bolt, then tighten nut.
Step 10: lower tongue jack, remove blocks.
Step 11: Take boat out after a few hours and test...
The first time you do it, you will be nervous..but...once you do it, it will seem like a piece of cake to change it if you so desire.
Steve | |
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Posts: 1023
| Thanks - I will try it - nervously!!!!!!! | |
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Posts: 4266
| Do dealers mount the outboard up as far as possible during rigging, or do you have to request it? | |
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| From what I know, the dealers will mount it in the recommended placement based upon their instructions from the boat manufacturers. I went round and round with the man who rigged my last boat and ended up settling on the third hole up...he wouldn't go any higher. In the end, I ended up moving the motor up on my own....
Now, my motor sits on a 4" setback plate that allowed me to move it higher yet...so I am right on the edge for handling purposes in cornering. I must trim down if I go into any type of turn....but...the higher the mounting, the faster the boat goes...to a point.
Steve | |
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Posts: 43
Location: Roch NY | Factory reccommendations are based on an 'average' usage of the boat (1/2 of full capacity, compromise on top-end and holeshot, typical activity/usage for the boat type), so for instance, if its usually just 2 of you in the boat, you can raise up the motor higher than original height, but performance will suffer if you then load it up with people/gear, etc. simply stated: you can optimize based on which performance aspects are most important to you.
Sounds like if you have a great holeshot now, then you can afford to give up a bit on that and gain a bit on the top end.
Keep in mind that every boat has a different optimal motor height, so you may find yours actually gets worse if you raise it up (either too much or even at all), but based on what you've mentioned, its doubtful. the tough part is knowing just how high to go, and if you really want to dial it in, then yes you most likely will be trying a few heights until you get it right
As you mentioned, the one critical missing link in this is the prop, however if your hole shot is good then I will venture a guess that you don't need to go any lower in pitch, but that is a consideration if you optimze the height and are still low on revs.
good luck | |
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Posts: 1023
| Thanks!!! Everyone has been very helpful. | |
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Moving motor up to improve performance?