motor too high and out of adjustment holes

lola12swim

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Jan 25, 2015
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Hi y'all I have an 18' lake sport center console with a 90 hp Yamaha and I need to lower the motor. I already have it as low as it will go with the stock holes,,, any suggestions short of cutting the transom down? Could you do it with a jack plate? Thanks in advance for any help y'all can offer!!
 

gm280

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First let me welcome you to iboats, Always great to have you aboard. :welcome:

Answer to your question is YES. A Jackplate will allow you to raise or lower the engine. But how do you know the engine is presently too high? Where if the cavitation plate sitting in relationship to the hull now? Is it even with the bottom of the hull or within an inch either way? Post some pictures of your setup and let us see what you're dealing with before doing anything else...
 

roscoe

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Most of the time, a jack plate will not allow you to lower the motor very far, before running into issues with the steering cable and tilting the motor.

What is the transom height of your boat?

What is the model number of your motor?
 

Bob_VT

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Yes I would be looking at the transom length and the yamaha's shaft length. If you are going to cut a transom I would say let's make sure that is the true problem.

How long have you had this boat? What is it doing? Do you know that the anti-ventilation plate is normally above the keel. Let's discuss this before a saw gets used.
 

lola12swim

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Yamaha 90 hp modf# 6h1l1008548 transom ht 21" water hits the cav plate and spashes back in to the boat..and when I trim up the prop blows out pretty quiick
 

lola12swim

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WIN_20150125_160259.JPG the piece of wood is flat on the bottom of the boat... I've had the boat for about a month
 

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Frank Acampora

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Believe it or not: With water rising up the engine leg and splashing into the boat, you may have the engine mounted too low.
 

smokeonthewater

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Looks pretty cut and dried to me.... 20" transom and antivent plate 5" above it.... It's a short shaft motor....


I see 3 options in order of best to worst

1: sell the motor OR hull and get one that fits the hull or motor.....
2: find an extension for the motor if one exists......
3: cough, choke, ugh...... look into cutting the transom down BUT I stress this as a last resort... a 15" transom IMHO doesn't have any place on anything longer than 12-14' except MAYBE a race boat....
 

ondarvr

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Can't really tell much from that pic, back up about 5 feet and take another one. No need for the board or the tape measure.
 

gm280

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One other issue is to post the engine model number. That will let everybody know if it is a standard shaft or long shaft engine. I think it is a combination of a standard shaft engine sitting on a 21" transom. But until pictures from a little further away so we can see all the transom AND the engine sitting on it, there is no absolute way to say... Try to frame the transom with engine in one shot...but not so far away that we can make out the sizes of each...
 

smokeonthewater

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Why are you guys having such a tough time with the pic... he explains that he put a board on the keel and measured from there up... you can plainly see the anti vent plate is 5" up from the keel... plus his water intake is way high also....


It's a short shaft motor on a long shaft transom.
 

Sea Rider

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If it's a short shaft engine sitting on a long shaft transom wil not produce any splash in/over transom whatsoever, once on plane with well trimmed engine and boat riding parallel to water surface will see the AV plate visually exposed, on choppy seas will have excessive aereation, worst on tight close curves.

To have water splashes inside transom water flow is hitting right over small upper water deflector plate, flow is not being nicely cut on the sharp edge found right under upper small plate and upper AV plate. Is your tech issue something like this example ?

Back Water Splashes.JPG

For clarification, post a pic of the entire rear leg to check its lenght.

Happy Boating
 

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Bob_VT

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Can't really tell much from that pic, back up about 5 feet and take another one. No need for the board or the tape measure.


Same opinion....... Back away from the hull and get a photo of the motor in relation to the boat....... a pictur with the motor straight don and you standing off taking a side view.
 

ondarvr

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Why are you guys having such a tough time with the pic... he explains that he put a board on the keel and measured from there up... you can plainly see the anti vent plate is 5" up from the keel... plus his water intake is way high also....


It's a short shaft motor on a long shaft transom.

My 19' CC has a stepped transom, the AV plate is about 3+ inches higher than the bottom of the boat. While you can speculate on the cause of the problem, a pic will tell everything.
 

smokeonthewater

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To me it looks like the AV plate is 2.5" above the board?

WELL YES you're right.... I was looking at what I thought was the cooling intake.... but I googled a pic of the engine and that's an exhaust relief... the water intake is much lower.... thus DUH I (like the O/P) was looking at the wrong plate....

sooooo the engine MAY still be a little high but MAYBE a different prop would help with the blowout issue and then MAYBE the splashing issue is from having the engine trimmed too low at speed...

so much for cut and dried.......
 

lola12swim

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Jan 25, 2015
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Okay.... ill try a different prop but after moving the motor down to the last hole its does not start splashing in to the boat until I start to trim up..no splashing when the motor is all the way down.. before I moved the motor it splashes in all the time
 

ondarvr

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Flat bottom aluminum boats don't respond to trim very well, it's not going to get up and fly like a bass boat. A different prop may help some, but it's not going to make a huge difference.
 

ondarvr

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And lowering the motor will probably reduce your top speed.
 
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