2.5l 200hp how much hp can I get from this motor and keep reliability?

**rgsauger** · 04-25-2012, 09:16 PM

I've got a 90 model 2.5 200 merc. What are some basic mods to pull more hp from this motor? Without breaking stuff, what is reasonable hp for this motor? I,m almost done rebuilding a Shadow tunnel bass boat and am just curious about motor mods. Motor has 120 psi all cylinders on comp test.

Thanks guys. I learn a ton here.

Rob

**Hank W** · 04-25-2012, 09:26 PM

The 1st recommendation I have is tighter heads. Talk to Jim Ruck or Jay Smith about the correct CC'ing of the heads. If it is an EFI & you don't mind spending the bucks you could get a Brucato SVS unit. Do away with the oil injection if you are going to rev over 6500 RPM. This may get you 25 HP ??? You will not be able to get any radical gains w/o going to 7/14 petal reeds plus porting. And if you are thinking of doing all of that, go for a used 260 or better. Just my opinion

**rgsauger** · 04-25-2012, 10:10 PM

Thanks Hank. The boat did not have an oil tank and the guy had always run premix. The flywheel cover says V200 on it. They sure look like three carbs. Air intake has a bunch of funky tubes on each side of it. I had to rebuild transom and floor before I could run it so have never had it out. Should be done in next 4 weeks! Had 120 psi on comp test spinning it over on jumper cables before I bought it. Wish me luck!!!

**rgsauger** · 04-25-2012, 10:13 PM

On heads, can I have mine shaved or go aftermarket? Are you looking for 140 psi or so?

**rgsauger** · 04-26-2012, 12:39 AM

Would opening up the exhaust make any difference or just make noise?

**Hank W** · 04-26-2012, 11:19 PM

Originally Posted by rgsauger

On heads, can I have mine shaved or go aftermarket? Are you looking for 140 psi or so?

Everything I have read & heard says 145 PSI tops for 92/93 pump gas. 120 sounds good for stock heads so the engine is apparently in good shape. You can send your heads off to be cut down or if you are in a hurry, some will swap your stock heads for the modified heads for a fee (of course). Ask around to see if you need to go richer on the jets if you increase the compression. In addition to the 2 names above, Eagle One does heads as well. But since you are in TX, call Jay Smith.
Yep, you have carbs. Some people remove that air box & add velocity stacks, but you would need to jet the carbs accordingly.

**Hank W** · 04-26-2012, 11:55 PM

Originally Posted by rgsauger

Would opening up the exhaust make any difference or just make noise?

If you do a few mods, opening up the exhaust might help a bit, but it WILL make more noise. Your stock motor will have an inner can inside to help keep it quiet & separate the spent cooling water from the exhaust gases. Lots of guys remove the can altogether, but I like to leave it in fishing motors & drill several holes in it near the bottom to line up with the following - You can do like Merc does on their High Perf stuff & drill holes in the bottom of the mid can, but that requires either pulling the powerhead or there is another way, which is a bit easier & involves pulling the lower motor mount yoke. When you put it back, turn the lower mount bolts around so it's easier to do in the future. It is a pain but less work than pulling the powerhead. If you do either, swap out the soft mounts for solid.

Just remember that most mods to a carbed motor may require richer jetting!

**rgsauger** · 04-27-2012, 12:03 AM

Thanks again. This rig should run upper 70's or better. Right now
, motor is off boat. Should I try to go ahead and get the solid mounts? All of my experience is small fishing boats and hi perf offshores. Have never reslly played with a tunnel before..,k

**FrenchPhil** · 04-27-2012, 04:56 AM

What boat ?

**Jay Smith** · 04-27-2012, 07:46 AM

Give me a call, I will be glad to help.. 1 281 576 5088 cst

Jay

**rgsauger** · 04-28-2012, 12:13 AM

Originally Posted by FrenchPhil

What boat ?

Shadow bass boat tunnel. Like a mod v hull. Very similar to laser hull. They were made in southern ky. Extremely light layup hull.

**rgsauger** · 04-28-2012, 12:15 AM

Thanks Jay. I am up on lake Houston. Look forward to meeting you soon. Will def be in touch. Rob

**johnboy 88 vegas** · 04-28-2012, 02:16 AM

I know that everyone here says to go with a 4 or 5 petal setup for under 8 grand but: when I put my motor together last time I went with the 7 petal with the hi-po reed blocks. I got the exaust chest cut out like a drag block at the same time with no changes to the stock 200 port timing. Something made a heck of a difference in acceleration compared to the old motor but I dont know if it was the exaust or intake since they were both done at the same time. It does have a little more hesitation off the line but once it gets over 2 grand its good. This was with a 96' model 200 block and 260 reeds/cages with 150/155 compression.