OS 65 VRM experience.

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tnt76

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I've recently kinda inherited a 40" deep v with an OS 65 inboard engine from my other halfs father. He bought this around 20+ years ago and ran it twice, decided it was all too hard and put it in a dark corner of his back garden shed. He knew I was into rc stuff and gave it to me a couple months ago.

It came with a few plastics props, which are full-ahead branded (old Australian brand) of 5070 5577 sizes. 55mm dia x 77mm pitch etc.

Anyone know much about these engines? Reliability, performance etc. Apparently it's on its second conrod, after his out if water tuning attempts didn't go to plan. Haha.

Any feedback on these appreciated.

Thanks
 
The OS VRM were good engines in their days. I like them and still have two 46 VRM. The case is weak so you need a hard mount to support the case. If you use a soft mount you need something like the Octura Humdinger.

Revving the engine out of the water will break the conrod. You need to check if there is damage to the case, and the piston/liner.

I think a 65 is too much engine in a 40" hull. The hull is probably meant for a 45

kez
 
Yes the connecting rods are a little weak and hard to find, I broke mine the first season took a year to find one. Good motor good carb stay in tune well, don't over rev it ! Use extra oil in fuel the lower bronze bushing is the weak link
 
Thanks guys,

I've had the engine apart and there are no visible signs of damage from the conrod breaking, I do have a spare rod, which I'm hoping to never need.

It is solid mounted to an aluminium cradle which then mounts on iso pads to the rails.

I spent a couple hours on the water the other day trying to get this thing up on a decent plane, trying different props etc, took cav plates off with no success. I got it home and put a straight edge over the hull to find an inbuilt hook on the last 3-4 inches of hull, currently waiting for epoxy filler to set and will sand down flat, seal and try again.

Also going to add a data logger to record some rpm's and keep it under the factory specs of 25000rpm and play with needle and pipe.

What would one suggest a prop size for this hull with sub surface drive?? I've got a couple metal blades now to try out.

Also, it has a 7F carb on it, which is different to the manual suggesting it have a 9B carb.
 
The 9B is THE best carb to have on that motor.
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Are you running surface drive or sub surface?
 
I have found it very hard to find any reference to a 7F carb. It is working ok, however I will keep an eye out for a 9B if it is the bees knees.
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It is a sub surface, shaft is running parallel and approx. 3/4" below vee. and prop is around 1 3/4" behind transom.
 
I've been looking up 9B carbs, is there two different mounting styles available? I can only find bolt on flange mount types, whereas mine is a sleeve/tube clamp on style.

7F Carb.JPG
 
That 7f carb was used on the (Disc ) motor ,the later motor used a drum which is where the 9B carb was used. As far as I know they will not interchange. The cranks and rods are also different
 
Thanks Larry, that makes sense as mine is the disc type. I suppose if its a worthwhile change to the 9B, I could turn up an adaptor. Is intake tract length critical? I'm thinking an adaptor could add a few mm to the length.

Also, I have an X455/3 here to test on it once it's back in the water.
 
If your just playing around I would leave it alone, your carb sits off to the top left and the newer motor puts the carb in the center. I feel the issue would be the air flow through the disc window. The only advantage with the 9B carb is a better low end adjuster no spray bar and I think the bore might be larger.

I have both of these motors and run them in 1/8 scale hydro using X 452 modified props , could have gone larger , the boats weigh around 15 lbs. call remi @ aeromarine he has one or two upgraded rods for your motor 302-628-3944

Good luck have fun. Larry R.

image.jpg
 
I would not sand the hook out of the boat. some people think its a defect, but it is there for a reason, and most certainly if its a Seaducer.. you will see a big difference when using the props the guys shared with you. always use metal. no plastic. plastic is not rigged enough. make sure to balance and sharpen prop. Look up your local boat club when racing is in season. you would be amazed at how eager the people are to help.

Good luck Jim
 
Thanks James,

The hull is an old Australian design from the 80's from Full-Ahead ( no longer running), along with the plastic props that were with it. I bought a few metal props, which were better, as expected, however I still could not get this thing up on a decent plane at all, seemed like the more I pushed it, the more it sucked down. 1/2 to 2/3 of the hull was still in the water. I adjusted cav plates ( no good) removed cav plates ( slightly better) and slightly moved prop depth (barely made a diff).

So I filled and sanded ( 1/8" thick) flat bottom of the hull and straight away it popped up onto a decent plane. That is until I hit a patch of reeds and busted rudder off, now waiting on new rudder with breakaway bolt.

This thing is only for fun, as it was given to me. I'm enjoying trying to nut it out and tune the hardware and setup to get it better.
 
Last edited by a moderator:
I failed to see the date of your first post. I did not realize Almost a month had passed. What I was going to suggest before taking out the hook was checking how far away the prop was from transom. My boat has a hook in it, and it did the same thing, I checked the builders web site, did some reading, and got some good incite from others on here. I found that my prop was to close to transom. and the water that shoots off the back of boat was over shooting the prop. the prop was not in the wake coming off transom. I made a change from 1 inch from transom to 2 1/2 and off she went. any way Glad you got it going in the right direction. Welcome to International Waters Trent.

Jim
 
Larry,

I have sent Remi a couple emails and as yet have not heard back, maybe you could help.

I have been measuring the OS with a depth micrometer to determine the timing and inputing into Marty's speadsheet. On a couple of measurements, I have come up a little diferent than the other OS 65 examples.

One being the conrod length and the other being (related) top of liner to piston measure. My spare conrod is in orig package and I have found it is for a .61 Heli engine, so I assume the one in the engine is the same (father inlaw broke original in 1980's). Are you able to tell me the length of your conrods in your two engines disc vs drum? My best effort shows between 40.00mm and 40.02mm with vernier calipers. The other examples are either 40.01mm ( 2 of) and 41.25mm (2 of).

Any help appreciated.Thanks
 
Last edited by a moderator:
Check this sight for OS part numbers http://www.osengines.com/parts/discontinued.html some of the 61-65 rods were used on other motors. Are you measureing the over all length ? You should be measuring the diameter of the crank pin,wrist pin and center to center of crank to wrist pin. I can disassemble both of my motors if needed. I know my 65 drum crank pin is 7mm in diameter the other is smaller. I suspect the length of the rods will be the same
 
Thanks Larry,

I've come across that OS page, It lists the drum version. I might go through the other engines and see if the same rod is used. I couldn't ask you to pull yours apart, it not critical for me to know the length at this point in time. I measured the from the upper edge of big end bushing to the lower edge of small end bushing then from lower edge of beg end to upper of small end then averaged the distance. My crank pin is 6.5mm. I'll keep looking around for more info.
 
This is a Aeromarine rod for a 65 disc motor. The measurements I took are as you described above. The crank pin hole measures 6.5mm 45.71mm outside 33.72 inside. Remi told me these rods are much better then the original, he also told me to be sure and remove any bronze material that might be scored onto the crank pin ( you'll see it ) if not you will damage the new rod bushing

image.jpg

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