Difference between mercury thunderbolt 1150 and 1500?

[Streffpilot]

As the title states I am wondering what the difference between the two engines are. I know displacement is the same, but what makes the 1500 a 150 hp and the 1150 a 115 hp??

 

[Texasmark]

Re: Difference between mercury thunderbolt 1150 and 1500?

It's more than carbs as I was told as I asked the question years ago thinking a carb swap would do the trick. Apparently they play around with reeds and porting and timing........and the jets.

First one I saw in action was a blue band and it was on a blue Hydrasport, maybe 16'. The guy was coming out of a marina, passed the buoys, punched it out and about 100 yards later passed another boat. In hitting the rather small wake, the HS shot into the air and I could see all the way under the boat; completely out of the water. Only thing in the water was some of the lower unit and some of the prop. Was awesome.

Mark

 

[Streffpilot]

Re: Difference between mercury thunderbolt 1150 and 1500?

Ok, now the big question: I am rebuilding my 1150 this winter. Any chance of me updating it to 1500 power levels? I a, very competent in the machine shop, but by no means an expert.

 

[Texasmark]

Re: Difference between mercury thunderbolt 1150 and 1500?

Ok, now the big question: I am rebuilding my 1150 this winter. Any chance of me updating it to 1500 power levels? I a, very competent in the machine shop, but by no means an expert.

Ask that question to Faztbullet, Steelspike, CharlieB, or Chris1956 to name a few. They can answer your question.

Mark

 

[wired247]

Re: Difference between mercury thunderbolt 1150 and 1500?

Blocks are different . The 1500 block has a big recess inside the cylinder wall that directs the intake charge through piston and acts as a third intake port of sorts. You could change blocks and use power port pistons if you want to duplicate a 1500 using the rest of your parts. Keep in mind the 1150 is a LOT stronger at lower RPM ranges and the 1500 only gains power on the top end at the expense of low end grunt. The reeds are also slightly different but thats no big deal if you switch to Carson or Boyesen reeds. Jetting and carb bodies are different too. Theres only so much you can do with 99 cubic inches, You can shift the power band up or down but when you do its going to have consequences.

 

[Streffpilot]

Re: Difference between mercury thunderbolt 1150 and 1500?

So in reality, i'd be just gaining mostly top end power by switching to a 1500, but I would lose a lot of low end torque and hole shot??

 

[wired247]

Re: Difference between mercury thunderbolt 1150 and 1500?

Yes. Thats exactly what would happen.

 

[Streffpilot]

Re: Difference between mercury thunderbolt 1150 and 1500?

Thanks, I'll keep my nice fat low end torque thank you very much!!!!

Thanks for the quick replys and saving me the headache of trying this idea.

 

[ehillger]

Re: Difference between mercury thunderbolt 1150 and 1500?

Thanks, I'll keep my nice fat low end torque thank you very much!!!!

Thanks for the quick replys and saving me the headache of trying this idea.

Hey, along these lines . . . I have a good 1500 block and a complete 1150 motor with a bad cylinder. I assume carb jets and ignition box need changing to get it to 1500 specs. Anything else need to change when swapping blocks???

 

[wired247]

Re: Difference between mercury thunderbolt 1150 and 1500?

Pistons are different too. Reeds are a little different too.

Hey, along these lines . . . I have a good 1500 block and a complete 1150 motor with a bad cylinder. I assume carb jets and ignition box need changing to get it to 1500 specs. Anything else need to change when swapping blocks???

 

[Faztbullet]

Re: Difference between mercury thunderbolt 1150 and 1500?

As stated the block is power ported, exhaust and intake port timing are slightly different, pistons are hi dome ported, reed blocks and reeds are different(banjo style), main jets a tad larger. The 150 only make 150hp at powerhead and about 120-125 hp at prop, that why when bia ratings started the 150 became the 140 and then the 140 became the 115. If you have the old non ported 115 you are about 95-100hp at prop.

 

[Texasmark]

Re: Difference between mercury thunderbolt 1150 and 1500?

I had the later version of the 115 mfgr'd. in '88 and it had the ported piston and 115 prop rated, 99 cu in. It was "Direct Charged" which was Mercury's fancy name for the porting. I don't know what other things were shared with earlier engines other than the ignition was CDModules with a switchbox, no belt driven distributor and surface gap plugs. It was a sweet running honey.

Mark