Question to the performance Merc experts

[Andys454]

Hey I have a 98 Crownline 202 with the carb 454 and brovo 1, I looking to add some power and speed to the boat anyone know where i should start? Keep in mind I'm not rich and can't afford a Blown 502 replacement engine! Just want to do maybe a heads and cam or something like that. About the only thing I have done to it so far is installing captains call Exhaust.

 

[TilliamWe]

Re: Question to the performance Merc experts

And as you now know, open exhaust won't add much by itself. But it does set the table for cam/head/intake upgrades.
I don't know the specifics, but there are some that do. Of course the single biggest piece of advice I can give you is, "don't build it like a drag car." You need low end torque, max WOT RPM in the 5000-5200 range, and you don't want a lot of overlap, because of water reversion issues.
Good luck.

 

[wire2]

Re: Question to the performance Merc experts

If you want more valve lift without more overlap, consider a set of roller rockers. I went from steel 1.5:1 to aluminum 1.6:1 on my 5.7 . I get more lift, less friction.
That was to go along with a Holley hi-rise aluminum intake, stainless headers, 'Vette aluminum heads and switched thru-hulls. I got lots more flow, shaved 200 lbs.
One thing about roller rockers; you may need to get tall valve covers. If the alternator is just above one now, it can get a bit complicated.

 

[picklenjim]

Re: Question to the performance Car experts

Re: Question to the performance Car experts

Keeping it conservative a cam change along with the proper springs and double roller timing chain set,roller rockers, aluminum dual plane high rise intake, and a good 750 CFM carb. When the heads are off have a 3 angle valve job done and springs set up by a competent machine shop. Should be able to easily make over 425HP with that motor.

 

[jtmarten]

Re: Question to the performance Merc experts

A REALLY good set of headers will get you 40+ HP, but set you back $2500. The capt's call nets you nothing with the stock manifolds in place. Power all comes down to airflow in ---> airflow out. You can build a 1000hp monster, but it'll choke with stock exhaust manifolds.

If you still have stock intake/carb: a Performer 2.0 and Holley 750 will give a decent boost. If you use a vac secondary carb, you should be able to cruise on the primaries and save fuel too.

Stainless roller rockers are a great investment too. 1.7 ratio will give more valve lift which means more airflow = more power. You'll likely need extra thick valve cover gaskets, or tall valve covers; nice way to dress her up too!

 

[Andys454]

Re: Question to the performance Merc experts

Ok I'm thinking about the 4barrel with vac secondaries. With a nice intake. and a carb spacer and maybe a better exhaust manifold. But how do you go about tuning the carb?

Dose anyone make a wet exhaust manifold for the Ls1 or Ls7 style corvette engines?

 

[Bondo]

Re: Question to the performance Merc experts

Ok I'm thinking about the 4barrel with vac secondaries. With a nice intake.

Ayuh,... Doesn't it Already have that,..??

Dose anyone make a wet exhaust manifold for the Ls1 or Ls7 style corvette engines?

No...

 

[Philster]

Re: Question to the performance Car experts

Re: Question to the performance Car experts

Keeping it conservative a cam change along with the proper springs and double roller timing chain set,roller rockers, aluminum dual plane high rise intake, and a good 750 CFM carb. When the heads are off have a 3 angle valve job done and springs set up by a competent machine shop. Should be able to easily make over 425HP with that motor.

Bingo. And don't forget the exhaust. I think 425 HP is very conservative. This is not far off from the Baja and 454 CID engine I had. The good thing is the Bravo One can handle it, but you do want to get all the trans/outdrive parts checked, adjusted and replaced as needed.

750 CFM carb. Ahhh.... can't ya just smell the raw fuel from here?

 

[jtmarten]

Re: Question to the performance Merc experts

Ok I'm thinking about the 4barrel with vac secondaries. With a nice intake. and a carb spacer and maybe a better exhaust manifold. But how do you go about tuning the carb?

Dose anyone make a wet exhaust manifold for the Ls1 or Ls7 style corvette engines?

A Holley will perform better than a q-jet and will be easier to maintain/tune.

Here's a set of wet exhaust manifolds:
http://cgi.ebay.com/ebaymotors/ws/e...7ffe10b36&rvr_id=&ua=WVI7&itemid=220469398649

 

[Andys454]

Re: Question to the performance Merc experts

A Holley will perform better than a q-jet and will be easier to maintain/tune.

Here's a set of wet exhaust manifolds:
http://cgi.ebay.com/ebaymotors/ws/e...7ffe10b36&rvr_id=&ua=WVI7&itemid=220469398649

Thanks for the link to the manifolds!!! DO the Ls engines share the same trans bolt pattern as the 454 merc?? how about flywheels? I have a Lsx 454 I was toying with the idea of installing it into the boat, Would the extra rpm of a small block help it go faster? The motor currently makes 600hp but It would need to be recammed to get a lower power band for a boat, so it would probably have about 500 hp with a 7000+ rpm red line. I think that would make a killer combo if it was setup correctly. What are your thoughts?

 

[Andys454]

Re: Question to the performance Merc experts

Can I just bolt on a set of 1.7 or 1.8 roller rockers? Will I need to check piston to valve clearance or will it be ok??? Can I buy the rockers for a automotive style 454 or are the different?
Thanks

Where is a good place to find performance Marine Merc Parts???

 

[Bondo]

Re: Question to the performance Merc experts

What are your thoughts?

Ayuh,.... How about You answering the questions posed,..??

I think you living in an uninformed Dream world....

 

[toolsinbox]

Re: Question to the performance Merc experts

i have an LSX engine on a stand in my garage. I will be putting it in one of my cars. It has 400 hp at 5000 rpm.

I would only run that in a boat if I had dry exaust. Then i would use it as is until the valves burned out.

The cam is wrong. The valve train is wrong.

the block will bolt up tho.

The flywheel is externally balanced. so keep that.

engine just not set up for a boat. You could start from scratch with it if you wanted. A gen IV intake wont bolt up to thoes heads so watch for that.

good luck.

 

[Andys454]

Re: Question to the performance Merc experts

Ayuh,.... How about You answering the questions posed,..??

I think you living in an uninformed Dream world....

If you not going to be constructive stay out of my posts. How about you inform me instead of insult me.

 

[Andys454]

Re: Question to the performance Merc experts

Ayuh,... Doesn't it Already have that,??

I thought it was a 2 barrel but now I need to go double check.

 

[Andys454]

Re: Question to the performance Merc experts

i have an LSX engine on a stand in my garage. I will be putting it in one of my cars. It has 400 hp at 5000 rpm.

I would only run that in a boat if I had dry exaust. Then i would use it as is until the valves burned out.

The cam is wrong. The valve train is wrong.

the block will bolt up tho.

The flywheel is externally balanced. so keep that.

engine just not set up for a boat. You could start from scratch with it if you wanted. A gen IV intake wont bolt up to thoes heads so watch for that.

good luck.

Why not run wet exhaust?? Will Stainless or titanium valve still burn out?
I know the cam would have to be drastically different. I would be running a Ls7 intake and keep it fuel injected. I'm not sure about the o2 sensors though in a wet exhaust probably wouldn't work.

 

[Andys454]

Re: Question to the performance Merc experts

A REALLY good set of headers will get you 40+ HP, but set you back $2500.

Where do they sell these headers?

 

[wire2]

Re: Question to the performance Merc experts

Where do they sell these headers?

Most are custom made. They're very labor intensive (read expensive) so few shops stock them. And then there's the different shaped ports, etc.

I made a set for my 5.7 out of ss tube, 1-3/4" inside 2", then with 3" inside 3?" for collectors. Water is pumped in between the 2 sizes.

They took many hours to make but sure sound nice.

 

[jtmarten]

Re: Question to the performance Merc experts

Where do they sell these headers?

Google search. Lots of performance marine suppliers carry them.
Join speedwake.com and offshoreonly.com, both deal mostly with high performance boating. You'll find tons of engine build info on both.

 

[Andys454]

Re: Question to the performance Merc experts

Google search. Lots of performance marine suppliers carry them.
Join speedwake.com and offshoreonly.com, both deal mostly with high performance boating. You'll find tons of engine build info on both.

Ok Thanks!! I was yahoo searching with out much luck.