T3 , T4, or SST120 merc info

[tunnel dorc]

Could someone tell me some info on these small V6 motors! Years made, size, hp ratings , articles, manuals --- anything! Thanks!!!!

[Raceman]

The first T3's were run by the factory in about '74 or maybe '75. The first rumors were that they were opposed 6's because they were so narrow by comparison with OMC's V4's nobody thought a V could be under the cowl. Soon after the time the factory developed these, they also adapted the previous T2 (6 carb inline 6) to the T3's housing which the privateer's had access to long before the T3 was made available. The first ones made available to the public were essentially stock 1750 powerheads on champ housings/super speedmasters, with plastic reeds, aluminum flywheels, timing locked at full advance and very few other deviations from stock. By the time the T3's were generally released as carb motors the factory guys already had the Bendix mechanical injectors on the team boats. There were also versions of the engine with 6 one barrel tillotsens similar to the T2X carbs. The first T3's and all the T2X's had the same Super Speedmaster as Merc had been using on the inline race motors. It was available in 14/15 and 1:1 gear ratio's and was adapted to the champ housing with an adapter plate with 6 studs. This may have been the weak link in the whole engine and it was shortly replaced with the 8 bolt housing and corresponding adapter plate. This housing allowed direct bolt on of the #6 and #4 SSM's without the adapter plate. As far as horsepower, hard to say because there were so many evolutions of the engine. In it's earliest form with carbs, maybe 200 or so at the propshaft. The T4 is a totally different animal. It's the race version of Merc's 3.4 liter 300. I can't think of anything outside of a few of the electrical pieces that interchange with any of the other V6's or the 3.4 liter production model. The gearcase is a #8 SSM and was never used on anything else. The early 3.4 production blocks were steel sleeved and the first T4's were chrome. The later production 3.4's were Nico's and done by Cosworth, but I believe the T4 program had been scrapped by this time. I've never seen a T4 with a Cosworth style block. There were also some T4's supposedly made with big bores yeilding displacements of 3.7 or 3.8 liters, but I haven't ever run accross one. One of the blocks that I bought in the box had a hand written tag attached to the injector that said 386 @ 7600. Although there were no other comments on the tag, I've always assumed this was HP and this engine had been dynoed. Most of the T4's were ultimately destroyed by Merc. Rumor has it that as many as 5 may still exist, but I only know of 1 that came out of the factory as a complete assembly. There are a number of powerheads around and several gearcases as well, but the housings are almost non existent.

[tunnel dorc]

Thanks again Raceman!!! What I'm trying to do is figure out if its feasable ( with my budget! ) to put a v6 merc on a small rec tunnel of mine. Motor weight is a big factor as the boats only 15', but the hull is really stout ( heavy!) That's why I feel 12" v6 is needed. Common sense says to put a v4 on it, but that doesn't sound very exciting! Plus almost everyone says the evinrudes are unreilable when modified. I met this man in my area ( Elsinore California) who used to race for Mercury in the early 70's, he has a garage full of older inline race stuff, some with the exhaust coming out the side of the motor etc... but not to much v6 stuff. Will any of his parts help me put together a T3 type motor, is this a feasable project or a waste of time!!! Can I purchase a complete motor at a reasonable cost!! Thanks again for you time!!!!

[Mark75H]

After a bunch of looking here and there I confirmed that the T-3 was first raced in 74, along side the T-2X which shared the up/down single ram tilt mid section. I think the first race was in late spring or early of 74.

Just like Raceman has been trying to tell me for years!

If the early version of the T-3 was about the same power as the T-2X we need to subtract a few hp, as the real life hp of the T-2X was never 200 hp.

Regarding putting one of these on your go fast boat, remember Speedmasters have no neutral or reverse, start in gear. Starting a cold motor in gear can be a real pain, not to mention dangerous.

To get an idea of what it would be like try this for a weekend: unhook your shift cable, bypass your neutral saftey switch, and use your highest pitch prop. Always make sure the area ahead of you is clear...you will not be able to stop.

In answer to your latest question....if there is a T-2X mid section there... you have hit paydirt. Take off the T-2X inline adapter and bolt on your V-6 powerhead. I would actually recommend a different boat to go with such a motor.

[Raceman]

I personally like the idea of the old T3 type engine for recreational use. My first go fast lake toy was a 15 Allison with a 1500J engine (the predecessor to the 1500XS) I upgraded that boat to a T3 as soon as I could get my hands on one. (still have pictures) As far as warm up. I always cranked it on the trailer with the prop half submerged, ran it for a minute and cut it off and shoved it off the trailer. One other option is to put a shiftable gearcase on it. The inline case will bolt up to all the adapter plates for those housings, both the 6 and 8 bolt. There are a number of people running similar conversions in outboard drag racing now. Virtually all the champ housings run have XR6 cases which is very similar in bolt pattern. The driveshaft of course has to be shortened and most people slot the housing at the front and run a shift cable down to the bottom of the housing, but it's a relatively simple mod. I used to run speedmasters on the 1500's on the same boat also and don't think they're that big an incovenience once you get used to it. There are champ housings of various year models around and most of the parts are interchangeable.

[tunnel dorc]

Thanks again for info !! Hey Mark what motor would you recommend for my boat, or what kinda boat should a T3 be on? Not trying to be smart ass just like input. The boat looks like a 21' Cougar MTR just a lot shorter, and the sponsons don't point out the front. It had an 80 merc on it and was very fustrating!!! I sold the motor, just couldn't look at it anymore! Rather not go out than be embarrassed! Another question?? Would I need a lift jack for a T3 type motor? Seems to me a tunnel kinda lifts it's self as it planes, but I don't know as the 80 never had air passing under it ( yes I hung over the back and looked at top speed (42 gps), and "No" I wasn't the only one on board) <Thanks guys>

[Raceman]

I think you'd have a real good chance of getting wet with any V6 on any 15' tunnel. That having been said, usually getting a 12" motor low enough is the problem. Doubt you'd be needing a jackplate and setback is probably the last thing it needs also. A 12" transom bracket has several more inches built into it than the stock motors anyway....can't remember exactly how much.

[tunnel dorc]

Thanks Raceman, that sounds like a great idea about the gearcase ! As far as getting wet, Yes I know V6 a risky proposition, but, I am willing to accept that! But, thanks for your concern! I'm not looking for ultimate top speed, just want it to get their real fast! So if I could see 70 that would be good. As far as getting the motor low enough, the boat has an aluminum mounting plate 4" off the back of the hull, that can be either lowered or cut, to get the correct height. Looks plenty strong. Any ideas about steering, gears/props, or props. Would I need to modify the xr6 lower unit with a low water pick up etc.. Thanks again for info!!!

[Raceman]

I said XR6 gearcase without thinking, but actually meant "big gearcase" in my comment about champ housings and ODBA race boats. I'm sure there's a mix of different, big gearcases adapted. Since you're not so concerned with top speed, a CLE gearcase solves your low water p/u problem and should be available cheaper than modifying an XR6 or buying a Sportmaster. There are a lot of pluses for a speedmaster... excellent handling, no steering torque, small blade won't have as much bow lift (blow over). That's if you can find a cheapie. As far as steering, you'll have to run steering arms, cables and pulleys with a champ housing or either fabricate a front steering arm and ride guide tubes because none of that stuff is present. I've seen it done but it represents a fair amount of fabrication. Another word of caution: I knew a guy that blew over an old Magnum tunnel that was bigger than 15' with an inline 150 and it killed him. Speed in small tunnels is dangerous.

[tunnel dorc]

O.K. Now you got my attention! Maybe I should look at v4's for that short tunnel. I bought a Sleekcraft 20' mod vp (light layup) with a 2.4 bp efi that had a bad piston, the motor is at the shop now getting rebuilt, will be running soon. How safe is this boat? I have heard these light boats blow over easy. The motor will be stock. What do you think of the evinrude v4 for my 15' tunnel. Your input is greatly appreciated ! <Dorc>

[Raceman]

I don't have any real experience with the Sleekcrafts. The only one I ever drove was a production boat with a windshield and a full interior. They made basically the same hull in either a straigh V bottom or a similar bottom with the two tunnels cut underneath. I think the Mod VP boat was a race version of the second, but not sure. The one I drove was the tunnel type and had a 200 OMC. It felt flighty to me in recreational trim, but the owner ran it on a local lake for years and never had any problems as far as I know. He'd run it real bow high too. As far as the 115 OMC on the little tunnel, one problem you'd have to deal with is the fact that they're all built for 20" transoms. Unless you could find an old racing center section (a lot rarer than Merc stuff) you'd have to do a good bit of build up probably. There are quite a few shortshaft inline 6 Mercs floating around and they might be a better choice. The powerhead off one of them will also bolt to any champ housing with a T2X adapter. (assuming the 6 cyl powerhead is '72 or newer)