65 HP long shaft on a zip

Questions about modifying a design

Moderators: ttownshaw, billy c

Post Reply
Dave goes fast
Posts: 8
Joined: Sun Aug 30, 2020 12:00 pm
Location: Lago Vista, TX

65 HP long shaft on a zip

Post by Dave goes fast »

Does anyone have any thoughts about me putting a 1974 Merc. 65hp long shaft on a zip. I'm going to be starting my build in the next month. I saw a post about putting steel strut rods and adding more battens but I'm wondering if anyone else has any Ideas. I feel the motor well will be a bit of a challenge. Or do I need a motor well? And How far do I go with looking for extra support? I know always better to over do it but I would like to stay in reality not redesigning the whole boat.

User avatar
vupilot
Posts: 3621
Joined: Wed Apr 15, 2009 7:36 am
Location: Indy
Contact:

Re: 65 HP long shaft on a zip

Post by vupilot »

I gotta ask, why so much power? The Zip's do great on 25-40hp.

User avatar
Roberta
Posts: 6746
Joined: Tue Jul 31, 2007 5:23 pm
Location: East Troy, Wisconsin

Re: 65 HP long shaft on a zip

Post by Roberta »

I put a Merc 500 on my Zip at it was great. About 34 mph top speed and cruised nicely at 4000 rpm and 28 mph. The Merc 650 is huge by comparison and could be problematic with poor balance and trim issues. The Zip is just not designed for sustained speeds above 30.

JMHO

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

Dave goes fast
Posts: 8
Joined: Sun Aug 30, 2020 12:00 pm
Location: Lago Vista, TX

Re: 65 HP long shaft on a zip

Post by Dave goes fast »

Here are a few reasons why. First it was what came on the donor boat and it was cheap and in good condition needs only regular maintenance to come back to life. Also yes I want to go fast. But I also want to be able to cruise at about 30mph without running up the rpms on an old motor. And every once in a while running it up to 40mph or so would be exciting. I have a 1976 17 foot Glastron I rebuilt with a 130 HP I/O and it tops out at 33 but I don't like hearing the motor running at 5000 rpms. I know it wont live long like that. (The boat really sits great in the water at that speed) My experience with motors has always been small motors working hard don't last long as big ones working less to achieve the same thing. As far as weight is concerned I don't think there is much difference between a 50 and a 65. I'll check that later today. I don't plan to carry more than me and one other person. I'm considering not even putting the rear cockpit in. Only reason I would or will is, I like the look of the boat with it. The lake that I will use this boat on is 60 miles long I would like to see more of it and not take all day to see more of it. (It's a river with a dam at both ends). Hope some of this justifies the 65. Now if anyone has any Ideas on how to best accomplish what I'm going to do that would be great. I appreciate this forum to get the help before I realize I shoulda coulda did something. Thanks to anyone responding.

User avatar
Roberta
Posts: 6746
Joined: Tue Jul 31, 2007 5:23 pm
Location: East Troy, Wisconsin

Re: 65 HP long shaft on a zip

Post by Roberta »

OK, the 1974 650 was the three cylinder version and only weighs about 20 lbs more than a four cylinder Merc 500. I assume you have this motor and does not power trim.

I would add some thickness to the transom motor board, raise the center of the transom to remove the cutout and create a hump to raise the cavitation plate of the motor to about the bottom of the boat at the keel, incorporate a motor well to beef up the transom structure, and maybe add some small knees on the battens by the transom. I would also consider increasing the angle of the transom to allow more bow down trim.

I have some pictures of what I did to strengthen the transom and motor well.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

User avatar
vupilot
Posts: 3621
Joined: Wed Apr 15, 2009 7:36 am
Location: Indy
Contact:

Re: 65 HP long shaft on a zip

Post by vupilot »

I'd look into building the Ski-Tow. Its rated for up to 70 hp.

Dave goes fast
Posts: 8
Joined: Sun Aug 30, 2020 12:00 pm
Location: Lago Vista, TX

Re: 65 HP long shaft on a zip

Post by Dave goes fast »

Yes you are correct it is the 3 cylinder. but it does have power tilt/trim also. Roberta thanks for the Ideas. What is the best way to see your pics. I'll look at the ski tow. but I already bought the plans for the zip.

Dave goes fast
Posts: 8
Joined: Sun Aug 30, 2020 12:00 pm
Location: Lago Vista, TX

Re: 65 HP long shaft on a zip

Post by Dave goes fast »

One other quick thought. If the 65hp doesn't seem to work out I can easily down size. I would rather that than try to up size. Looked at ski tow, sticking with the zip.

User avatar
Roberta
Posts: 6746
Joined: Tue Jul 31, 2007 5:23 pm
Location: East Troy, Wisconsin

Re: 65 HP long shaft on a zip

Post by Roberta »

All the pictures I posted in my Zip Thread are gone because the host went south. I do have all the pictures. Here are some regarding the motor well and transom reinforcement. And a picture of my Zip with the Merc 500 short shaft motor.

Roberta
Attachments
Madison Boat Show 079.JPG
interior 003.JPG
carlings 002.JPG
Motorwell 011.JPG
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

Hercdrvr
Posts: 1244
Joined: Mon May 11, 2015 12:52 pm
Location: McKinney TX

Re: 65 HP long shaft on a zip

Post by Hercdrvr »

65 hp Merc weighs 190 lbs, a new Yamaha 40hp weighs 214 lbs, build a good motor well to tie it all together back there, Strap it on and floor it, it’ll be fine. That said, I would be respectful of rough water.
Throwing more HP into the equation to try and go faster in a boat doesn’t have much effect. I thought my 90 hp Malahini would be way faster than the typical 60 hp Malahini. The difference is maybe 5 mph faster, maybe.
Also, I have seen a number of builders start a build based on a good old motor they already have to later upgrade to a modern 4 stroke engine. Not saying you will, but it happens. Old motors are noisy, smoky and cantankerous, Even my last generation 2 stroke Yamaha is a little offensive. And put a good size fuel tank in it because 2 strokes are gas sucking machines. Best of luck to you on your build, look forward to seeing it progress.
Matt B
Attachments
7F0A19CE-1161-4D2C-8935-682AC1CB2881.jpeg

User avatar
vupilot
Posts: 3621
Joined: Wed Apr 15, 2009 7:36 am
Location: Indy
Contact:

Re: 65 HP long shaft on a zip

Post by vupilot »

All good points Matt, I hate that they are so heavy and bulky compared to the old. Even a new 40hp looks out of proportion on a Zip. At 150lbs and reinforced over what the plans called for I still cringed on every pot hole hit on the highway seeing that 1975 Merc 402 bounce around in rearview mirror. Our terrible roads up north never helped.

Dave goes fast, Not sure if you have seen it in pictures here but there was a modified 85hp Zip at a couple of the past Gatherings. So its been done with success before. This one was stretched and the cockpit modified as I recall. I forget the gentleman's name at the moment.
20130920_080346.jpg

Dave goes fast
Posts: 8
Joined: Sun Aug 30, 2020 12:00 pm
Location: Lago Vista, TX

Re: 65 HP long shaft on a zip

Post by Dave goes fast »

Thanks for the pics and info. I think my plan for now is to add 2 more hull battens and 2 more knees and put kevlar cloth between the layers of transom. I will have a well also. I will have too figure out my spacing for the extra battens. I'd like to run them as far forward as possible but that will change where the original plan hit the forward hull and that may be not so desirable. I ordered wood today. Moving forward!
One other thought whoever mentioned me going to a 4 stroke is a possibility at some point I really don't like 2 stroke stink and noise but I'm gonna try it for a while. I've never had one (2 stroke) but always comment when i see one and say I'm glad mine isn't a 2stroke. but I'm gonna go down that road for now because of price.
Thanks Ya'll!

Post Reply

Return to “Design Modifications”