TRS to SSMIII conversion??????
 

I am converting a 302 Formula from TRS to Speedmaster III. I was going to maintain the current crank shaft center for the Speedmasters. I have since been told that the Speedmasters need to have a higher drive height. Somewhere in the order of 1 1/2 to 2 inches higher than the existing TRS. The reason I am told is that the SSM is a "semi-surface piercing" drive. If I leave the drive at the same heaght as the TRS, I would have to trim the heck out of them to get the performace I'm looking for, if at all. Can anyone out there agree or disagree? :confused: Thanks!!!!

I would agree that the #3 ssm is deeper than the TRS, about 2 1/2 inches. I dis-agree that it is a surface or semi-surface drive. If you mount the #3 in the same location as the TRs you will have serious drag issues. My suggestion would be to go up 1 inch higher than the TRS.

I like the thought of only raising the drive about an inch. I'd like to keep the weight as close to the keel as possible, and I really want to avoid clearance problems with the factory hatch, transom exhaust locations, swim platform, etc. Thanks for the reply!

Wasn't the SSMII, 2 that is, a direct replacement for the lower unit of a TRS? That would be nice to find, easy swap if true.

Yes the SSMII was a direct fit on the TRS upper. The SSMIII is way different. The drives are larger and much heavier than my old TRS. I can testify after carrying them into my garage. It has a much larger gimbal assembly, too. I have already purchased reconditioned SSMIII units, so I'm into this project with both feet. No looking back now. Thanks for the reply!

Hi CIG3. I called Mercury Racing Division to ask about this. They tech told me the crank shaft centers are within 1/8" of each other (trs and ssmiii), and that I would be OK mounting them at the same height. I have several other sources telling me to raise the drives anywhere from 1 to 2 1/2 inches. I'm guessing that these sources are talking real world experience and Mercury is quoting scripture from the manual? Any information you can pass along would be a huge help. Thanks!

Are4 the new units 3's or 3A's That may make a difference in your decision, same length but diff prop possibilities.

3's

From a straight up length difference, Mercury is correct. But from a drag aspect the #3 has more due to the length and mass of the lower. Also remember that you will be running a differant prop configuration that gives you much great bite than the old clever or bravo style prop you are running with the TRS. This all factors in. The one inch up is very conservative as I don't know your power combination or how you use your boat. Two inched wouldn't hurt you if everything would still fit under the hatch as you want.

The III at the TRS level will be slower. The lower is bigger and the IIs props are more efficient as semi surface piercing.
1" up is VERY conservative. Most old TRS boats could run the TRSs 1" higher and go a couple mph faster.
If you can, raise it 2".
It might be worth checking out SSM drive height on similar size V hulls before you recut your transom.
Gary

"IF" everything still fits under the hatch. My entire bilge is stripped out and the boat is at my glass guys shop about an hour and a half away. I'm pretty convinced that I need to move the drive height up. I can always space them down if need be. I need to get inside the bilge and take some detailed measurements. Any concern with regards to handling when moving the drive/engines up two inches? I know it will shift balance, but do you think it would even be noticeable? The boat is a 24 degree V, no steps or notches. I'm going naturally aspirated and hoping for around 500HP. I'm not going racing, but I wouldn't mind getting to Atlantic City ahead of the rest of the gang. Thanks for the input!

I saw a 357 Formula for sale in the classifieds with SSMIII. I sent him a note asking just that. Looks like the general consensus is, drives up 2". I have not started looking for props yet. If the drives are going up 2 ", should I be looking for 4 blade props rather than 3 blade? Thanks for the reply, Gary!

One note.
I dont think you can run spacers on old IIIs. IIIAs will accept spacers. Check on this first for your drive.

Go with the two inches up. And three blade props will be your best bet. Your still not gonna be to the point of surfacing the props. Also the small shaft stuff should be easy to find in three blade. Try BAM in POmpano or Intense Marine Miami.

Talk to DJD on hear. I know that everyone was telling him to go up 2 inches and he went 3 and I think he was very happy with that set up. The TRS set up on your 302 is VERY low. I measured mine and my prop shaft is 1 foot below the bottom of the boat!! Go as high as your engine covers will allow is my suggestion, IMO your drives will still be to low.

Jon

CIG3, Thanks again. I have seen quite a bit of small shaft props for sale. Just have to figure what pitch to start with. I have been dealing with BAM Marine for a lot of my OEM mercury parts. I'll be sure to contact them when I'm ready for props.

Gary, thanks for letting me know about the potential problem regarding spacers. I have number to call Mercury Racing tech department. I'll give them a ring during business hours tomorrow. I'll let you know what they say about SSM3 spacer availability. Thanks again for your help!!!

Jon, I'll try to contact DJD. I'll take some measurements to see just how high I can go. I have some Stellings exhaust coming in. I'm sure they'll add to the clearance issue, too. Glad I posted this thread! Everyone has been awesome! If I hadn't asked you guys, I'd have been dragging my drives all over the Atlantic! Thanks again, Dave.

It's not spacer availability that's the issue. The early IIIs did not have a long enough verticle shaft o add spacers in between the upper and lower.
As for the heright. Keep in mind that not only is the III designed to run much higher, it's also several inches longer. That allows an even higher drive height, similar to adding an extension box.
Once again start looking at factory installed drive heights on similar boats.
I did this on my last cat and had great results. BTW, on that boat the prop shaft was 1 1/2" above the bottom of the hull.

why 2 dogs how has your project turned out??? I would love to see pictures of the progress.

Why do that. TRS, MCIII, MCIV, MCIIIA's are all discontinued.
If you change to aby of those drives, you will have to change your Gimbals. Why not go with the Konard drives. You won't have to worry about the hieght and they are good for and up to over 800hp. Give me a call and I will discuss this with you.
We can save you some money in the long run, plus drives and parts are no problem getting. Call me before you make the change. Your boat will run faster. Call me at; 954 237 0332

Did you ever think of a complete drive replacement for your TRS? Konrad Marine has one that requires no modifications and I am told very reliable.