---

I am currently going back and forth with a very reputable marina in the heart of Washington DC on repowering my 1993 Montauk 17. I am going with a new Yamaha F90. I'm happy with their quote but they are telling me I need to have a jackplate installed because the interior transom is to shallow to accept the lower mounting bolts.

The dealer has studied numerous pictures I gave them of my current rig with a 90HP Evinrude. They said there is a special Evinrude mount which clamps the bracket's mid-section using the original hole locations which are near/at the waterline.

I have done a ton of research on this and I have read nothing about needing a jackplate to install a Yamaha F90 on a Classic Montauk. I've actually read people recommending against it due to excessive weight (which is already a concern of mine with the 90hp 4 stk) and pushing the CG farther aft in the boat.

The dealer, who also maintains the USCG outboards here in DC, said that most dealers use lag bolts in the lower mounts (which I have read about) but they are a bit "sketchy" with this method.

I don't want to make it sound like they are ripping me off. I have talked to both their sales and maintenance department in person and like what they do. I am an educated customer.

Sorry for the long post, just want to provide the details. Anyone have any advice? Thanks!!

---

Since 1986 the splashwell was deep enough for the Standard Pattern.

You do not need a Jackplate to install that motor.

Have they measured anything?
Have them take a look at this drawing.
https://www.whalercentral.com/article...icle_id=82

You should be able to drill several of those lower holes.
1. Green
2. Yellow
3. Red

Measure the splashwell yourself and let us know.
The top holes in the transom should be around 1 7/8" almost 2 inches. Start there first and then measure down for the lower bolts on both the inside and the outside of the transom.
That way you would be sure where the lower hole is going to go.

Mount the motor 2 holes up to start with.
https://www.whalercentral.com/article...cle_id=106

Here is another member that had that motor mounted on an older 1978 Montauk where the splashwell was much shorter.
His is mounted all the way up and can not move it unless they drill new lower Green holes.
https://www.whalercentral.com/forum/v...pid=163534

Again, you should be able to drill the RED holes but measure twice before doing so.
Minimum, drill the Yellow holes but again, measure.

---

You probably have 3 choices:
1) mount new engine in the blind holes and suffer a lot of performance
2) redrill new holes and fill in the old holes and mount properly like Joe mentioned above. Not a bad option.
3) buy a jackplate and mount it in your current holes and raise the engine. Probably the best performance and best looking install but you will setback the weight aft and lose some reverse thrust depending on height,

I would go the smallest setback jackplate and raise it up 3+ inches from the keel nd enjoy it. Not to mention 2-3mph faster than stock with the right prop.

---

Matt - Follow these ^^^^ guys advice.

Stick to your guns. Your dealer is uninformed and needs to be schooled.

Print out the diagram and GIVE it to them.

2 holes up.

It is your 10-11K, make them do it the way YOU want.

---

Thanks SO much gents! What wealth of information. I love the willingness of this community to support each other with no expectation of return. I look forward to paying it forward.