Is the motor height going to be an issue?

[S.E.R.E.NITY NOW]

I know that the cavitation plate should be level with the bottom of the transom but I can't raise my motor any higher than an inch. As it is now the clamps are only half an inch from the top of the transom and cavitation plate is still 1.5" below the transom. Is this enough to worry about? It's a 9.9 on a 13ft Smokercraft so I would like it set to be as efficient as possible. Overall weight is roughly 575 lbs with just me in it with roughly 100lbs of it being at the bow.
I could add a jack plate but I'd rather not. Especially if the benefit to getting it level with the transom will be miniscule compared to how it sits now.

 

[Still Afloat]

Yes, this could be an issue. It will impact top speed and it could cause problems like porpoising.

Is the motor properly matched to the transom height? If that is a long shaft outboard the transom should measure 20 to 21”. If your transom is around 15” then you will need a short shaft outboard.

It could also be an extra long shaft motor on a 20” transom so we really need more information.

A possible alternative to replacing the OB or changing shaft length is to rebuild the transom, if it makes sense.

 

[airshot]

Cause a problem...probably nothing serious, but your motor will not be effiecient. Wrong shaft length for the transom. As mentioned, loss of speed and issues in shallow water with prop hitting. Either go with a jack plate or have a riser welded/ bolted to the transom to get the motor higher. If performance is not an issue, then go for it, but, if it were mine, I would fabricate a riser to get the motor the correct height, but then again I am kinda picky about things being correct....

 

[S.E.R.E.NITY NOW]

Cause a problem...probably nothing serious, but your motor will not be effiecient. Wrong shaft length for the transom. As mentioned, loss of speed and issues in shallow water with prop hitting. Either go with a jack plate or have a riser welded/ bolted to the transom to get the motor higher. If performance is not an issue, then go for it, but, if it were mine, I would fabricate a riser to get the motor the correct height, but then again I am kinda picky about things being correct....

I know that the cavitation plate should be level with the bottom of the transom but I can't raise my motor any higher than an inch. As it is now the clamps are only half an inch from the top of the transom and cavitation plate is still 1.5" below the transom. Is this enough to worry about? It's a 9.9 on a 13ft Smokercraft so I would like it set to be as efficient as possible. Overall weight is roughly 575 lbs with just me in it with roughly 100lbs of it being at the bow.
I could add a jack plate but I'd rather not. Especially if the benefit to getting it level with the transom will be miniscule compared to how it sits now.

The transom measures 20.5" the motor is a 2023 Mercury 9.9 long shaft but I havnt actually measured it. Specs say 20" shaft.

 

[flatheadsteve]

Looks like the perfect opportunity to install a jack plate. Others have nailed the performance issues from it mounted to low. If that transom measures 20" than perhaps the motor is a xl 25" shaft.

 

[Crazyboat]

Bear this in mind, when turning you may well find out it is unsafe. You will have too much "rudder" in the water and turns will be sharper than normal. Get a jack plate or, beef up the back of the boat with wood. you can use a 1/2" plywood on the outside another on the inside of the transom and fill in the center space with scrap wood and a bunch of silicone or 4200 like stuff. It's what I did as a kid, money was tight and I used what I had. It worked great, never had an issue. I recall the new mount being too wide for the clamps but I shaved about 1/16'th off the inside and outside plywood and the engine clamps fit just fine. If you have the money, go with a jackplate so you can adjust your height.

 

[S.E.R.E.NITY NOW]

Looks like the perfect opportunity to install a jack plate. Others have nailed the performance issues from it mounted to low. If that transom measures 20" than perhaps the motor is a xl 25" shaft

It's definitely not an XL. I'm not sure why it's off by that much. Model number says it's a long shaft and measuring it puts it around 21 depending on how I have it trimmed from the top of the inside of the the braket to the cavitation plate.. Will a jack plate move the motor back also?

 

[Still Afloat]

It's definitely not an XL. I'm not sure why it's off by that much. Model number says it's a long shaft and measuring it puts it around 21 depending on how I have it trimmed from the top of the inside of the the braket to the cavitation plate.. Will a jack plate move the motor back also?

I have a 2023 Lowe 1448M with a 20” transom and my Suzuki 9.9/20, Zuki 25 and Merc 25 jet are all too low. It seems that for whatever reason the outboard manufactures aren’t quite in sync with the aluminum boat manufactures.

In my situation there could be a happy medium by adding 1 to 2” to the transom. I want to have the capacity of running a prop or jet OB. (Still some testing to do.) A jack plate is a possible but, not preferred solution because it will shift the motor weight farther astern.

So maybe I’m in a similar situation, adding another 1.5” of transom shims to the ~1” shim that are already there for testing might not be a good idea. In my case the motor clamps would not have a good grip on the transom with more than a 1” shim.

My thought is to weld the upper 1x1” square tube “shim” to a couple of aluminum plates, one on each side of the transom. Add shims as needed and simply use two heavy duty welding clamps to hold the works in place long enough to try it out. If done right you could shim up a couple of inches and the outboard clamps would still have something solid to hang on to

Use at your own risk but, that’s my plan.

 

[LDUBS]

It's definitely not an XL. I'm not sure why it's off by that much. Model number says it's a long shaft and measuring it puts it around 21 depending on how I have it trimmed from the top of the inside of the the braket to the cavitation plate.. Will a jack plate move the motor back also?

Was that 9.9 made by Vandelay Industries?

 

[MDCrappie]

Get some plate and bolt together. Or get someone to bend some plate for you. Either into a "c" or two pieces into "L" and sandwich together, thru bolting transom. I only use a 4hp on this but would have no issues running a 9.9. In this pic I was testing height so only screwed, but now it is held together with 4 bolts thru transom. Don't remember exactly but I think I picked up like 5mph top end.

 

[Bailey Boat]

Ya'll going about this the HARD way. TH Marine makes what they call a "Mini Jacker" that bolts to the transom and is fully adjustable that allows the use of a long shaft on a short transom. I used it to mount a long shaft Merc (20") to the short (16") transom of my 1448 Lowe. Sold the boat and motor separately and the boat buyer asked ne to remove it.
It is for sale in the classifieds if you're interested. https://www.tinboats.net/threads/th-marine-mini-jacker.50635/

 

[S.E.R.E.NITY NOW]

I have a 2023 Lowe 1448M with a 20” transom and my Suzuki 9.9/20, Zuki 25 and Merc 25 jet are all too low. It seems that for whatever reason the outboard manufactures aren’t quite in sync with the aluminum boat manufactures.

In my situation there could be a happy medium by adding 1 to 2” to the transom. I want to have the capacity of running a prop or jet OB. (Still some testing to do.) A jack plate is a possible but, not preferred solution because it will shift the motor weight farther astern.

So maybe I’m in a similar situation, adding another 1.5” of transom shims to the ~1” shim that are already there for testing might not be a good idea. In my case the motor clamps would not have a good grip on the transom with more than a 1” shim.

My thought is to weld the upper 1x1” square tube “shim” to a couple of aluminum plates, one on each side of the transom. Add shims as needed and simply use two heavy duty welding clamps to hold the works in place long enough to try it out. If done right you could shim up a couple of inches and the outboard clamps would still have something solid to hang on to

Use at your own risk but, that’s my plan.

Get some plate and bolt together. Or get someone to bend some plate for you. Either into a "c" or two pieces into "L" and sandwich together, thru bolting transom. I only use a 4hp on this but would have no issues running a 9.9. In this pic I was testing height so only screwed, but now it is held together with 4 bolts thru transom. Don't remember exactly but I think I picked up like 5mph top end.
View attachment 120191

Did that put the cavitation plate level with the transom or slightly above?

 

[S.E.R.E.NITY NOW]

I have a 2023 Lowe 1448M with a 20” transom and my Suzuki 9.9/20, Zuki 25 and Merc 25 jet are all too low. It seems that for whatever reason the outboard manufactures aren’t quite in sync with the aluminum boat manufactures.

In my situation there could be a happy medium by adding 1 to 2” to the transom. I want to have the capacity of running a prop or jet OB. (Still some testing to do.) A jack plate is a possible but, not preferred solution because it will shift the motor weight farther astern.

So maybe I’m in a similar situation, adding another 1.5” of transom shims to the ~1” shim that are already there for testing might not be a good idea. In my case the motor clamps would not have a good grip on the transom with more than a 1” shim.

My thought is to weld the upper 1x1” square tube “shim” to a couple of aluminum plates, one on each side of the transom. Add shims as needed and simply use two heavy duty welding clamps to hold the works in place long enough to try it out. If done right you could shim up a couple of inches and the outboard clamps would still have something solid to hang on to

Use at your own risk but, that’s my plan.

Ya'll going about this the HARD way. TH Marine makes what they call a "Mini Jacker" that bolts to the transom and is fully adjustable that allows the use of a long shaft on a short transom. I used it to mount a long shaft Merc (20") to the short (16") transom of my 1448 Lowe. Sold the boat and motor separately and the boat buyer asked ne to remove it.
It is for sale in the classifieds if you're interested. https://www.tinboats.net/threads/th-marine-mini-jacker.50635/

That also moves the motor back does it not? I'm trying to avoid that. The way the seat is mounted now the reach is perfect.

 

[thill]

This will be different advice from most, but I would recommend that you RUN IT FIRST. Worst case, it will give you a good performance baseline. Why do I recommend this?

I had one that was very similar, with either a 9.9 or a 15 HP. It sat exactly as yours did. I put blocks under it, and it ran fine, but the height really bothered me.

Eventually, I modified the transom and raised it up to be flush with the transom... It ran terribly. Blew out constantly on all but straight runs. Porpoised on the straight runs. Not nearly as stable, regardless of trim angle. I cut down half of my modification, and it ran better, but it ran best at the height of using blocks, just like your pic. At least it was permanent, now. I really didn't expect that. Something strange about the hull, compared to others. I never really figured out why, and just stopped worrying about it. My hull was a 1957 Crestliner, by the way.

By contrast, on my Princecraft, running a 35 and a 50 HP, raising it up to just a touch over flush with the bottom made a HUGE improvement in performance, so again, I would tell you to RUN IT, then go from there.

 

[Still Afloat]

Ya'll going about this the HARD way. TH Marine makes what they call a "Mini Jacker" that bolts to the transom and is fully adjustable that allows the use of a long shaft on a short transom. I used it to mount a long shaft Merc (20") to the short (16") transom of my 1448 Lowe. Sold the boat and motor separately and the boat buyer asked ne to remove it.
It is for sale in the classifieds if you're interested. https://www.tinboats.net/threads/th-marine-mini-jacker.50635/

I’ve looked at the Mini Jacker and no thanks. It’s just cast aluminum and wood. Besides, I’m trying to avoid pods and moving the motor back will only make balance issues worse.

 

[LDUBS]

This will be different advice from most, but I would recommend that you RUN IT FIRST. Worst case, it will give you a good performance baseline. Why do I recommend this?

I had one that was very similar, with either a 9.9 or a 15 HP. It sat exactly as yours did. I put blocks under it, and it ran fine, but the height really bothered me.

Eventually, I modified the transom and raised it up to be flush with the transom... It ran terribly. Blew out constantly on all but straight runs. Porpoised on the straight runs. Not nearly as stable, regardless of trim angle. I cut down half of my modification, and it ran better, but it ran best at the height of using blocks, just like your pic. At least it was permanent, now. I really didn't expect that. Something strange about the hull, compared to others. I never really figured out why, and just stopped worrying about it. My hull was a 1957 Crestliner, by the way.

By contrast, on my Princecraft, running a 35 and a 50 HP, raising it up to just a touch over flush with the bottom made a HUGE improvement in performance, so again, I would tell you to RUN IT, then go from there.

This is terrific advice. If it runs well, why change it. Don't fix what ain't broke.

 

[S.E.R.E.NITY NOW]

This will be different advice from most, but I would recommend that you RUN IT FIRST. Worst case, it will give you a good performance baseline. Why do I recommend this?

I had one that was very similar, with either a 9.9 or a 15 HP. It sat exactly as yours did. I put blocks under it, and it ran fine, but the height really bothered me.

Eventually, I modified the transom and raised it up to be flush with the transom... It ran terribly. Blew out constantly on all but straight runs. Porpoised on the straight runs. Not nearly as stable, regardless of trim angle. I cut down half of my modification, and it ran better, but it ran best at the height of using blocks, just like your pic. At least it was permanent, now. I really didn't expect that. Something strange about the hull, compared to others. I never really figured out why, and just stopped worrying about it. My hull was a 1957 Crestliner, by the way.

By contrast, on my Princecraft, running a 35 and a 50 HP, raising it up to just a touch over flush with the bottom made a HUGE improvement in performance, so again, I would tell you to RUN IT, then go from there.

Solid advice all around. Thank you.
I do plan on running it first before I make anything too permanent. My issue is my lack of experience. I'm not entirely sure what I'm looking for or feeling for to say yes or no as to how it should be set. That's why I was looking to put it at the industry standard and go from there. The 1" I raised it with the square tubing is easy to try out and change and see what difference I notice. I am a little worried the clamps are too close to the top of the transom.
Here's how it looks raised 1" from where it was. Still 1.5" below the transom if going by a straight edge along the hull.

 

[airshot]

See the example MDCrappie showed, easy, simple and it should work. I would make it wider and longer to attach to the knee brace. Then again, I believe in overkill to be safe.

 

[S.E.R.E.NITY NOW]

See the example MDCrappie showed, easy, simple and it should work. I would make it wider and longer to attach to the knee brace. Then again, I believe in overkill to be safe.

That's what I'll end up doing if it needs to come up more. The adjustability of a jack plate would be nice but I really don't want to move the motor back any further.

 

[Zum]

Theres a few different homemade versions of risers...a few on this site, seen in the search.
Have you been in this boat yet?