400-650 Mercury Thunderbolt information needed

[xanaphyst]

Howdy,
I'm over in Houston area and looking for an old mercury thunderbolt 4 cylinder (or maybe 3 cylinder) to get restored for a future tunnel boat project. I'm getting a disparity in information surrounding some of these engines. First and foremost the engine will have to be in the lighter 4 cylinder range and I don't understand if the 650 is heavier and if it indeed exist in both 3 and 4 cylinder versions. Second question is there a "preferred" engine (40-65) in all these years do to some reason like ..... This one had the best porting, or that one had a reliable ignition or something like that.

Thanks for whatever help you may have ...... or information about where I should be looking.

 

[racerone]

The 400 / 450 / 500 were 4 cylinder and painted " cloud white up to 62..------The early 650 was also a 4 cylinder with more displacement and a bigger motor with more weight..---I do not believe the 4 cylinder 650 was ever painted white.---Up until about 1966 they used the wonderful belt driven magneto.------A simple and reliable. device that you can maintain yourself.------In 72 the 650 went to 3 cylinder and not a very good model in my opinion.----Stay away from the 3 cylinder 650 !!

 

[xanaphyst]

Alrighty then... I'll scratch 650's off the list due to weight.

I take it the 402 is a 2 cylinder version .... hows that compare to the 400 4 cylinder ? More torque but not as smooth perhaps.

 

[racerone]

I would not put a 2 cylinder 402 on any boat that I own.----Find out what a 4 cylinder 650 weighs first.----It is heavier but not that much.

 

[Faztbullet]

A short shaft 50 is what ya need.

 

[Texasmark]

I certainly agree with racerone on what not to get. On Faztbullets comment, I grew up in Pasadena and we used to water ski and have boat races in the river across from the San Jacinto Monument back in the late 50's.

The hottest engines in the race circuit were 4 cylinder Mercs, only 40 hp (OEM design value, not racing value after mods) back then, with the bullet nosed High speed lower unit turning a small diameter 2 blade, high pitched, bronze prop. I accompanied a friend and his dad who used to race... I was just an onlooker, wasn't very bright then. His dad liked to also race the old 4 cylinder opposed cyiinder Mercs too.

The little 4 cylinders on small, light hulls, like 2 and 3 point hydroplanes, and some bullet shaped mono-hulls, had a spring loaded throttle you squeeze to accelerate and if the operator let go it would spring back to either idle or shut the engine off (safety device), never got into which it did.

To get on plane the driver would squeeze the throttle to WOT and the prop would blow out, but the boat would start moving. The driver continuously repeated the pulsation of the throttle and the boat's momentum kept increasing until it got on plane. Once on plane the prop locked up and away they went.

Besides the racing bullet nosed LU, some had horn type exhaust ports coming right off the block and pointing toward the rear of the boat on these 4 cylinder Mercs, VERY loud!!!! Never saw an OMC engine at these races.

Edit: It just hit me: I think the sponsor of those races was Bayshore Boat Club. Which is an idea for you to google boat clubs in the Houston area and surely you can hit upon folks who have engines and adaptations to support your endeavors.

 

[racerone]

Any pictures of the opposed 4 cylinder Mercury motor ??

 

[merc850]

I'm pretty sure Mercury never built opposed engines except for engineering exercises.

 

[racerone]

Texas----Says these opposed 4 cylinder Mercury motors exist.-----I would like a picture if possible.

 

[Texasmark]

I'm pretty sure Mercury never built opposed engines except for engineering exercises.View attachment 354720

" His dad liked to also race the old 4 cylinder opposed cyiinder Mercs too."
This is wrong. I should have said OMC 4 cylinder opposed engines too.

Since we are talking about memory back to the late 1950's......The friend as I recall had a 1950 vintage, light blue, round cowl 25 hp Evinrude on his boat, while I had a 1959 18 HP Evinrude on my boat at that time. We were in high school together and neighbors. His daddy had the opposed engines on his boat that he raced.....the son, my friend, didn't race...just tagged along with his dad to the races for the fun of it and invited me on several occasions. I think the dad had 2 of the "OMC" opposed engines, the 4 cylinder on his boat and the 2 cylinder sitting on an engine stand in his garage. I think they were 12 1/2 and 25 HP stock rated.

Sorry for the error and enjoyed the historical pictures and info!

I went with them to the boat races where the Mark 55 4 cyl inline Mercs were popular and those were the engines I was referring to. Remembering there was in fact an OMC following and it was the opposed engines. I do recall on one visit A racer with a sharp nosed monohull was racing and nosed into a wake and upon clearing, the prop caught and the boat lunged forward slamming him backwards, (you raced on your knees) hitting and injuring the back of his head on the flanged flared scoop attached to the single carburetor protruding out the front of he engine, unprotected.....apparently knocking him out as his boat stopped. We saw it happen and the emergency assistance folks that went out to his boat.

 

[racerone]

Correct OMC built an opposed 4 cylinder.------It was the 4"60" model.-----Heard one running at the Constantine meet years ago.-----Wonderful piece of machinery.