Mercury Mark 58, Why The Preferences?

John (Taylor) Gabrowski · 11-14-2005

Lately there have been real good preferences expressed about Mercs Mark 58 outboards that were some of Mercs earliest 44s as were the Mark 55A and Mark 55A(E) engines. What makes them so special to some people? I have at least one Mark 58 block sitting as an empty spare. Any enlightenment?

**crankbearing** · 11-18-2005

Hey John,

It was my understanding that the 58 block has less of a water jacket than the newer 44 blocks. As well I think they cc better then the newer style engine. I have always hunted for 58 blocks and not 58A They just always seemed to be faster when assembled.. 58 blocks were Super Thunderbolt and 58A were Full Jewelled Super thunderbolt along with the 400, 450, etc...

Regards..

**mercguy** · 11-18-2005

Originally Posted by crankbearing

Hey John,

It was my understanding that the 58 block has less of a water jacket than the newer 44 blocks. As well I think they cc better then the newer style engine. I have always hunted for 58 blocks and not 58A They just always seemed to be faster when assembled.. 58 blocks were Super Thunderbolt and 58A were Full Jewelled Super thunderbolt along with the 400, 450, etc...

Regards..

easy Dave, don't reveal all "our" secrets........

**crankbearing** · 11-27-2005

BOOOOOOO YAHHHHHHHHHHHH????

OOPS!!!!

Regards,

**Ron Hill** · 11-27-2005

When Merc went to the three screw port covers, the in take side was much larger, but you lost crankcase pressure....

Actually, I thought the early blocks had more water in the jacket and thinner sleeves....they have more holes, too, as a restule they didn't idle as well as the hotter running motors, but they ran faster....I', pretty sure the early 58 E's had very high compression head...I KNOW the 55 E's did...The black blocks with the 89 serial number as the first two numbers...

Add: I thought all 44 blocks said "SUPER THUNDERBOLT" on the them.

30's said TURBO FOUR
40's said Thunderbolt
44's said Super Thunderbolt.....Only from memory, so, like often, I could be wrong...

**crankbearing** · 12-01-2005

Hey Ron,

Nope the 58 from what I recall was the only super thunderbolt, the 35A got full Jewelled Thunderbolt and the 58A and into todays 44 got Full Jewelled Super Thunderbolt designation...

Regards,