Mercruiser "Tempest".......Opinions !!

[Stan]

What is the Mercruiser "Tempest" ? 454/300 HP...from the mid 1980's ?

Is this a good engine ...and what does the tempest stand for ? Can it be built up ?

thanks

Stan

[superhatz]

The Tempest is a 350 cu. in. engine. The brochure I have says the motor is 9:1 compression ratio and has a single 4 barrel. They came with an MC1 drive that looks like a speedmaster of sorts or a TRS. If I remember right the engine also had a forged crank and pistons and 4 bolt mains. But I'm not sure.

I hope this helps.

[Gearhead99]

Everything I remember about the Tempest 300 was that is was an overrated 350. Preformed much like the 260 hp, 350. Not very impressive.

[Murphy]

The Tempest 300 was a hi-performance 350 produced in 1985 and 86. It has a forged crank, forged rods and forged TRW pistons with full trough valve relief. and a 4-bolt main. It was rated on paper at 300 hp. Very strong, reliable engine. We pulled mine this winter for an overhaul and after 14 years, the engine was in unbelievably good condition internally. Less wear than we could believe. The machine shop guy said the block had received extra machinining of internal surfaces and raceways that he doesn't see very often. Before the overhaul it was capable of turning 5400 rpm and would push the boat 60 on the speedo (unconfirmed) Mine came with a 4 bbl Quadrajet carb and Alpha 1 drive. For the overhaul we kept the block, crank, and cam but replaced the original lightweight heads with a set of 1974 angle plus 492 heavyweight high compression heads. The new pistons are Kieth Black quench style and produce about 9.4:1 compression. Other upgrades include new lightweight I-beam rods, a GM cast iron high-rise dual-plane manifold, and a Holley 4011 650cfm carb. The heads and manifold were gasket matched. If our calculations are correct, it should produce about 350 hp when all is said and done. Should have everything back in the boat next week and we'll know more. Anyway, the Tempest is a great platform for upgrade in my opinion. With gas prices likely to continue rising, it's a reasonable compromise between performance and economy.

[BigGrizzly]

I was never impressed with them. some people though they were great, some though they were just hype. A friend of my sister had one in a wantabe Donzi, she beat him with a 302 Ford with a 500cfm Holley. He then pulled it out dynoed it to find it had only 280 horse. What a disapointment for him. He dumped a lot of money into it and finally beat my sister's sixteen. When he got done the only thing left eas the block and rods the rest was changed.
Randy