74 Starcraft Holiday resto

[Watermann]

WaterMann... Does your Chieftan 1970 have the standard BIA engine mounting template holes??? Mine seem about 1/16+ off on the height(top to bottom holes)

No my Chief is a Mercruiser IO but my SS and SN both have BIA pattern holes, I drilled them myself in the SS to mount the CMC TnT unit since the old Merc TOP has 2 clamps up top there were only 2 lower holes and they didn't match anywhere close to the BIA pattern. I filled in and covered the old mounting holes from the dorm fridge Chrysler than was originally on the SS with an outer AL plate to replace the old wooden pad..

 

[SkidRowBill]

Thanks Watermann... I imagine that 1/16th is just a drilling error...

 

[Watermann]

Thanks Watermann... I imagine that 1/16th is just a drilling error...

Happens to the best of us. I would wait until you have the motor ready to mount on the transom and then make any needed corrections to the holes.

 

[SkidRowBill]

WaterMann... I called SeaStar and they said that I need a 13Ft NFB... I also looked at the Tilt Version $75 more... any comments... I am thinking that I can sit closer to the helm if I can tilt the wheel up 24 degrees...??? also they said that the hole in my dash is standard 3 1/4 inches... mine is 2 1/2... was that an issue for you that you needed a larger than OEM hole to fit the new Manual rotary helm into???

 

[Watermann]

Yeah I had to drill my center hole out larger for the new helm. Tilt wheel would be nice alright but I got the regular, I think you were quoted a low price though I seem to remember it being almost $150 more for tilt. I opted for a seat slide instead.

 

[SkidRowBill]

Thanks WaterMann... SS 15713 Tilt $285.00 delivered... I am hopeing that this will offer options when it comes to placement of the "Captians Throne"... I have to purchase a Jack Plate to mount this motor on this boat... I found a 2.5 inch setback at Bobs Machine in Florida... it was recommended to get the least setback I could find by the Man that I purchased the motor from... he queeried a friend that was very knowlegable in the jack plate engineering field and explained the tourque that the transom recieved when applying power to the boat... he also suggested that a 1/4 inch aluminum plate inside the stern would be helpful... he also said that the starboard is a bad idea because it shrinks under presure...

 

[Watermann]

Yeah I don't know if he was talking about the same thing but most likely, I have an upper and lower plate that the mounting bolts go through to distribute the force.

They're called a CMC transom washer plate... the top one I turned around the imprinted writing so I didn't have to look at it.
Made of strong 3/8" 6061 T6 alloy aluminum (not cast aluminum), the CMC transom washer can eliminate bolts “biting” into transoms and can more evenly distribute loads on high performance engines.
Hole centers: Top Plate – 12 7/8" Bottom Plate – 9 7/8"

 

[SkidRowBill]

Thanks WaterMann... I saw these plates $35.00 at Bobs... I use metal depot and can get 16 X 12 1/4 inch plate for half of that, I am not sure what it will do if the motor wants to rip the transom off from the back of the boat... if I had purchased the correct transom length motor I would not be worried... some people have said that I am worried about nothing, just check the bolts on occasion and there will be no problems... I have bought some SS to build a brace which will bolt to the front of the transom and 1 foot back on the gunwales... I take disabled veterans, some in wheel chairs, out fishing and site seeing... if something happened it would be a real tragedy that would be hard to swallow if it was a failure on my part to take proper precautions...

 

[Watermann]

Well if things were to come apart then they would have to start somewhere and with those 3/8" plates it won't be there at the 4 bolt connections attaching the motor to the boat at least.

I wouldn't agree that there's nothing to worry about. The 4 SS bolts are 1/2" dia with nyloc nuts making a total of a 2" in dia, all the force is applied on those bolts beginning at the center of the transom and that's why there's a knee brace that transfers force to the bottom of the hull. Braces on the sides of the transom that tie it into the sides of the hull. Braces on the ends of the gunnels tied into the transom. Once the decking goes in you can even add thick AL angle braces screwed into the deck and then the transom giving even more area for the force to be spread to.

No one piece of boat structure takes the full brunt of the OB power but everything has to be in good order so there's no weak link that will start a chain reaction. The more you add that ties that transom to the rest of the hull is a good thing. Adding to the transom thickness isn't really a bad thing but it does nothing to stave off the failure to have proper structure that transfers the power to the hull.

My V5 SS has no Z channel at the bottom of the transom inner skin only 1/4" bolts that attach through the transom wood. It had no side brackets that tie the transom to the sides of the hull, so I added my own using the existing 1/4" bolts through the transom and solid rivets through the sides of the hull.I don't know why they didn't add the side braces but it could have something to do with there being 2 very large knee braces framing the bilge area. The knee braces not only rivet through the bottom but also to the deck support stringers.

 

[Watermann]

Added side braces, your boat should already have them.

Seen in this transom test fitting pic below. You can figure a way to tie your deck support stringers into the transom like my double brace set up and it will add even more rigidity to the transom. The ply I have there is covering it up some but the knee braces solid rivet into the deck support stringers and of course through the bottom of the hull. I replaced all of those rivets too with new solids. Also the SW is bolted through the transom and solid rivets to the top of the knee braces, then the SW ties into the gunnels which I added more rivets too. The SW is a major player in the aft support structure. I added a piece of .100 AL to the front of the knee braces too as a way to strengthen tying them together up front and to add a firewall of sorts between my bilge and the fuel tank fore of it.

Just trying to show you there's more to think about and ways to strengthen the connection between your boat and the motor that have already been designed by SC rather than just trying to add thickness to the transom which has it's limitations.

 

[SkidRowBill]

Nice clean setup Watermann... My issue is that I have to use a Jack Plate and lift the motor 5 inches... the plate that I have chosen has 2 inches by design and another 4.5 inches in manual lift... I am told that this affair will twist the top of the transom backwards when I apply power(the amount of tourque will depend on the trim angle)... the prop some 25 inches below a motor mount that is 5 inches above the mounting bolts, and top of transom... if anyone has real world experience with such a set up I would love to hear it... in florida most everyone runs a jack plate(some are 14 inches straight back) to set thier motor back into clean water and to lift the vi-something plate and lower unit nearly out of the water just to gain 5 or so MPH... But all of these guys are running newer glass boats and the engines are jacked up once the boat is on plain to lessen the tourque applied to the Jack plate... I have yet to talk to anyone who has this affair on an older alluminum boat... I have talked to people who run them on newer Lunds and the like but not with an incorrect transom lower that is 5 inches too long...

 

[SkidRowBill]

Wow... Watermann... I like your style... I am happy to see that you believe as I do that an older boat can use whatever help we might dream up to make them stronger... I like the idea of the deck stringers tieing into the transom, also the sides tieing into the transom... my worries are the top center of the transom and I believe that I must tie the top of the transom into the gunwales to counter the tourque effect of my rediculous setup...

 

[SkidRowBill]

Looking at your transom height it occurs to me that it is cut low for no other reason than the engine tourqueing the transom... do you agree???

 

[SkidRowBill]

seeing and going through all this is shedding another light on the use of an out drive or IO...

 

[Watermann]

Alright Bill you win and I don't know what else to say to help you along...

I thought you might have noticed something similar to what you're describing in my build, guess not so below's a better pic of my set up. Not sure you're going to find that certain guy here with that exact set up like yours and my SS build might be as close as you can get. My 140 HP Merc is still hanging on after a week long sea trial every day and you saw some of my strengthening mods that I did or described in my previous posts.

Good luck!

 

[SkidRowBill]

Wow... Fantastic... A jack Plate... 4 to 6 inches set back???... looks to be 4 inches higher??? is your lower to long??? No matter the length it must behave like mine will... Don't get me wrong... I am very interested in your mods... do you believe that your setup is tourqueing the top of your transom??? 140HP and I am running 60HP... I am feeling much better now... it appears your wood is an inch or so higher than the aluminum on the transom, did you set the engine at 1 7/8th inches below the top of the wood or aluminum, as someone showed earlier along with the template??? I feel that I can get 3/4 of and inch or a little more if I measure to the top of my wood and would not have to jack it so high... verry sweeeeet setup now that I see one up close...

 

[SkidRowBill]

Can you take a pic that shows the entire engine and back of boat... Please...

 

[laurentide]

Can you take a pic that shows the entire engine and back of boat... Please...

There are a bunch in his build thread. Check it out.

That CMC unit is elevated due to the setback. The further back off the transom you go the higher the prop should be.

 

[Watermann]

Bill the thing is you don't want to make your transom non standard, I used the same template to bore my mounting holes so that if some day I wanted to get a new motor then I could loose the CMC unit and bolt the new motor right on my transom.

No the 140 doesn't even budge the transom even with. a WOT hole shot and motor only settles in a little as seen in the videos, I tested her out real well while wearing my PFD and kill switch lanyard :lol: There is a little creaking sound but that's the seat pedestal head making the sound complaining a bit on take off with my 270 Lb buddy sitting in it. :

Your 60 will be fine I'm thinking and with a few strengthening mods your mind will be at ease.

 

[jbcurt00]

I know its an extremely bitter pill, but if you look thru some long shaft motors w height added to 15in short transoms topics, the vast majority arent satisfied w the less then expected results

Spending more money to add a bracket to accomodate the wrong motor sounds like bad money after bad money esp if you have to install it such that wont accommodate a correct height 20in motor. Thats likely to effect re-sale....

You've gotten good advice from guys that have very different setups on similar sized boats.

There is a great deal of info in here, if you cant get posts HERE to help answer your questions or want additional info, GO LOOK thru other topics. So you'll see how dozens and dozens of build challenges were overcome, how numerous builds proceeded from point A (bought a boat) to point Z123 (splashed a boat). Yep, it sounds like a lot of work, because it is, but it helps prevent a huge 25% restocking fee mistake.....

I dont know who you bought the motor from, but if he's demanding a 25% re-stocking fee on a motor you havent taken delivery of yet, I dont know that he's the go to guy for questions and answers that dont reinforce a poor purchase (AND sales) decision. Again, I dont know the details of your motor choice, but if you gave him accurate info specific to your 1974 boat, there should have been no way he didn't know the 25in motor was the wrong one.

IMO, if you have questions about how best to build your transom and all that entails, you could do no better then the advice you've already gotten, repeatedly.....

Add my desent for adding Starboard anywhere on the transom.....

Good luck w your project, hope for the best, plan for the worst.