Supercharged Vortec?

[Doc_Rhen]

I am considering having a boat built (20-22ft aluminum sled) and in looking at available powerplants I saw that KEM was producing a Supercharged 6.0L turning out 502hp. I was wondering if anybody has experience or insight into the preformance and reliability of this powerplant in relation to the HO 8.1L. I was also curious if this motor would require a pump upgrade to a HJ 213 or 241. My morbid curiosity with this powerplant stems from being one of the last folks on the water interested in slalom skiing and nearly drowning last week while trying to get up on a ski behind an underpowered boat. I also test drove a 24' Thunderjet with an 8.1, nice boat but there is no way I could have skiied behind it.

[BIGCSS]

I am considering having a boat built (20-22ft aluminum sled) and in looking at available powerplants I saw that KEM was producing a Supercharged 6.0L turning out 502hp. I was wondering if anybody has experience or insight into the preformance and reliability of this powerplant in relation to the HO 8.1L. I was also curious if this motor would require a pump upgrade to a HJ 213 or 241. My morbid curiosity with this powerplant stems from being one of the last folks on the water interested in slalom skiing and nearly drowning last week while trying to get up on a ski behind an underpowered boat. I also test drove a 24' Thunderjet with an 8.1, nice boat but there is no way I could have skiied behind it.
The only benefit you would get with upgrading to a HJ213 is the hydraulic reverse bucket and more zinc anodes in this application and also about a $4500 upgrade (some builders do offer an electric/hydraulic shift for the 212 for a little less than 1/2 the cost of the 213 and Waterdog has it on his 23.5 ft sled.) The 213 is essentially the same pump as the 212 but with a bigger input shaft for use with diesels and the other features I mentioned before. I wouldn't personally run a HJ241 with anything smaller than a 8.1L (I have a 390hp Kodiak 8.1L with a 241 in my 24 ft sled) or a 4.2L Diesel like a Yanmar 6lp, due to the torque needed to spin the larger impeller. The supercharged motors really don't make the power until you get above the rpm ranges that the Hamilton pumps are designed for (above 4200 rpm). That being said there are several people that have used the supercharged motors with the Hamiltons that really liked them. There has been a fair amount of discussion on the Riverjet Forum's about the motors. One thing I have seen is the Marine Power Version of the supercharged 6 Liter has a better powerband and also has an intercooler to eliminate heat soak that the Kodiak motor does not. I normally am a bigger fan of Kodiak's marinization, but think Marine Power has done a better job with the supercharger so far. Anyway that is my couple of cents, I hope some of this info helps.

Cam Stanyk

[WaterDog]

As Cam pointed out you don't need a 213 or 241. For your use I'd look into a AT312. I'm not sold on these small engines being super charged, but that is me. I'd rather have big block for low end torque at an rpm range I can use. :twocents:

I'm courious as to why you don't think you couldn't ski behind the TJ with the 8.1L?

[ICHTHYDEMON]

A force feed small block or a Big block?

I'll take the Big Block thanks.

[rv10pilot]

The 241 would be too big for a boat in the 20-22' range. Plus you would definatley have to go with a big block, adding even more weight. I am a fan of Hamilton pumps so I would go with the HJ212. As for engine I would also go with the Supercharged 6.0. Even if it doesn't have the life as a big block you are still talking about well over a 1000 hours on the engine. More than most boat engines see and probably more than you would put on it.

The other thought is going with a 383 Stroker - light and lots of power.
Either way with this amount of power go with the 4.0 turbo impeller.

I am considering having a boat built (20-22ft aluminum sled) and in looking at available powerplants I saw that KEM was producing a Supercharged 6.0L turning out 502hp. I was wondering if anybody has experience or insight into the preformance and reliability of this powerplant in relation to the HO 8.1L. I was also curious if this motor would require a pump upgrade to a HJ 213 or 241. My morbid curiosity with this powerplant stems from being one of the last folks on the water interested in slalom skiing and nearly drowning last week while trying to get up on a ski behind an underpowered boat. I also test drove a 24' Thunderjet with an 8.1, nice boat but there is no way I could have skiied behind it.

[Doc_Rhen]

As Cam pointed out you don't need a 213 or 241. For your use I'd look into a AT312. I'm not sold on these small engines being super charged, but that is me. I'd rather have big block for low end torque at an rpm range I can use. :twocents:

I'm courious as to why you don't think you couldn't ski behind the TJ with the 8.1L?

The thought that I could not ski the TJ comes from the test drive, It took forever to get on plane and seemed to top out at 30 mph (lowrance GPS) after 25-30 seconds:shrug:. Most slalom skiing happens at 28+ mph but dragging halfway across the lake to get there you will be so tired that making a cut would be impossible....but I guess you would be so afraid to fall you might be more apt to avoid a crash:grin:.

PS thanks for all the replies, additional thoughts/comments certainly appreciated>

[rv10pilot]

Sounds like that Tjet wasn't set up right or something else was going on. I have a 24' boat and 8.1 and HJ212 and I could rip your arms off. Tops out at about 45 mph. My boat is not a Tjet but even my 21' Tjet that I had before had about the same numbers with a smaller engine.


The thought that I could not ski the TJ comes from the test drive, It took forever to get on plane and seemed to top out at 30 mph (lowrance GPS) after 25-30 seconds:shrug:. Most slalom skiing happens at 28+ mph but dragging halfway across the lake to get there you will be so tired that making a cut would be impossible....but I guess you would be so afraid to fall you might be more apt to avoid a crash:grin:.

PS thanks for all the replies, additional thoughts/comments certainly appreciated>

[fishkisser]

Shoot my little marine power 350 chevy can pop my 20ftr up in the time it takes to light a smoke....

[Doc_Rhen]

Interesting, maybe I will revisit the Tjet out of curiosity, we are talking about a 24' boat with a hard top, 108" beam and .250 bottom at 84". I imagine it weighs loads more than a 20' but if it should jump, I might have another look.

[WaterDog]

Something is not right with the TJ. I know rv10 and my boat weigh considerably more than the TJ an our boats jump right out of the hole and on step. It should have a 4.0kw impellor in it. Check that the bucket is all the way up. :shrug:

[Doc_Rhen]

Something is not right with the TJ. I know rv10 and my boat weigh considerably more than the TJ an our boats jump right out of the hole and on step. It should have a 4.0kw impellor in it. Check that the bucket is all the way up. :shrug:

In retrospect I also wonder if we were running without an alternator and on a poor battery. We actually got stranded and ended up returning on the kicker. We shut down the main so that I could test out the TR1 Autopilot on the kicker, after we messed with the kicker (rope start) for about 2 minutes we tried restarting the main and got the "dead battery clicks.":shrug: It seemed odd that we would be able to start in the tank at the dealership, and at the dock just fine, but then after running for 10 minutes and shutting down for a couple minutes...nothing? Other question, are your engines the regular 390hp or the HO 420/425 hp 8.1L?

Thanks,

Dr. Rhen

[BIGCSS]

In retrospect I also wonder if we were running without an alternator and on a poor battery. We actually got stranded and ended up returning on the kicker. We shut down the main so that I could test out the TR1 Autopilot on the kicker, after we messed with the kicker (rope start) for about 2 minutes we tried restarting the main and got the "dead battery clicks.":shrug: It seemed odd that we would be able to start in the tank at the dealership, and at the dock just fine, but then after running for 10 minutes and shutting down for a couple minutes...nothing? Other question, are your engines the regular 390hp or the HO 420/425 hp 8.1L?

Thanks,

Dr. Rhen

RV10Pilot, Waterdog's, and mine are all built by the same manufacturer and are all the standard 390 hp Kodiak motors. Also these boats are considerably heavier than a Thunderjet (tons of underfloor bracing)and get on step in an instant. I have personally seen Waterdog's boat considerably overloaded (several people and camping gear for almost a week in Hells Canyon) and it still gets on step instantly. My boat will do the same with even more weight, but I have a 7 ft bottom and 241, where he and RV10pilot have the 212.

Cam Stanyk