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Mercruiser 5.7 260hp

Remember what I said before. The lAND AND Sea stern jack will make you faster than your friend's jet boat with out giving up your stock, reliable motor or your fuel economy. If any thing, it will help out an gas consumption. So what if Mercury says not to use them. They also tell you to use only Mercury oil filters and gear lube! My friend has been running one for about 8 years without any problems at all. It's an easy 6-8 mph on your boat without pulling the engine or even removing the valve covers! boatman
 
I will definitley do a Land & Sea stern jack plus I am adding the Mercruiser SS lower unit with a high water pickup. Do you belive this combo will give 5-8 mph??? I still want to up my horsepower from 260hp to at least 300...
Will the out drive mods be the cheapest way to go?? Still have not found a stern jack anywhere but from Land & Sea there was one on Ebay but was sold before I got it! Anyone out there with a used one I am ready to buy Thanks Chris cvx16cvx@yahoo.com
 
The stern jack should give 6-8 mph with ease. You may have to change prop's. In most case's, you can run one size bigger when using a stern jack. I will be on the lookout for one. If I have any luck, I'll let you know. boatman
 
i thought they quit making the stern-jack for the alpha

daren

going to roller fulcrum roller tip rocker arms stepping up from 1.5 ratio to 1.65 ratio will almost get you the added hp you want

this will make you cam have more lift !!
and you have a lot less friction on top
this is probably the cheapest and easiest hp you can get

daren
 
Sorry to disagree, simply adding roller rockers, even ones with a larger offset, wont net you any noticable change.
 
I agee! Opening the valves just a small amount with a stock cam doesn't mean anything. A larger cam, different intake and carb, and a good ignition system might get you 25 to 30 extra hp.Even with small gains you increase rpm's and decrease reliability. To make large hp gains, you need to change heads or have port work done on yours. It all comes down to what you want. Just remember, the more you want to play, the more you gotta pay! boatman
 
Okay so I am going to stroke it out to a 383. I am choosing heads. I run 99.5% of the time in fresh water.. Still I am unsure if I should go Aluminum heads...Edelbrock, Trick Flow, Ar or go with some DART iron heads.
They all make marine spec heads.
I still want to keep a idle 500rpm to a redline 5500rpm.
I am definetly going with an Aluminum Intake. Probably a Sea Demon Carb. Maybe Edelbrock matching Carb and intake..
Sp any Ideas am I thinking straight??
Is 375hp to 400 hp too much for an Alpha SS drive matched to a 21' Enchanter hull??
 
Good choice to keep the rpm's down. Merc recommends keeping the propshaft speed down to 3750rpm's.
I am watching closely to see what to do with the 305 in the diplomat!!!!
Can you see a 383 in a 17ft boat????
Why would increasing valve lift from @480 to @512 not increase horsepower and rpm range?
not to mention the reduction in rotating friction??????
 
A small increase in valve lift without a change in valve timing(duration) just makes to hole a little bigger while still being fed by the same carb, same ports and same or less compression. While it may increase hp, the gain would be so small you would never notice. As for roller rocker's, they would help some, but again not enough to notice. Reducing friction is always a good thing, but it doesn't show up until you get into the higher rpm range. Back in my drag strip days, one of my racing buddy's had a machine shop and a dyno. He took a 350 Chevy that hit the dyno at 388hp with conventional 40 weight motor oil and switched to synthetic, hp was the same below 4000rpm's. At 6000 rpm's, 8 more hp. Synthetic oil will make more difference than just roller rocker's because it reduces friction in the whole engine. boatman
 
By the way, a great choice in heads for what you are wanting to build and keep the rpm's down would be the newer vortec cast iron heads. You can buy them ready to bolt on fairly cheap. boatman
 
Are there any Marine Spec Aluminum Heads out there?/ Is anyone manufacturing these for small blocks?? Any recomendations. Is aluminum a mistake? I am in fresh water 99.5% of the time.Remember this is going to be a 383 stroker idle at 500 rpm redline 5000-5500 Looking for 375hp..Single carb,MSD marine distributor, spark box, etc. etc.
<pre class="ip-ubbcode-code-pre"> </pre>Still havent found an affordable header set up!!
 
You can use the Edlebrock heads. I don't know of any difference in heads for marine or auto. Some of the ads that you see for crate motors say not for marine use. The reason for that is the gaskets. I checked into this for myself a few years ago. Everyone I called said that the metal on the head gaskets were not designed to withstand the corrosion that is seen in a marine engine. But don't just take my word for it, look in your hot boat magazine's and get some toll free number's and start calling. See if you get the same answer's that I did. The gm vortec head will give the performance that you are looking for. GM offers a 350 crate motor with these heads(or they did) that I think was rated at 375hp. I built my own copy of that same engine with a brand new set of vortec heads and it ran great. Only problem was, I put it in a baja. One of my weaker moments! boatman
 
I was wrong, the 350 h.o. crate motor is 330hp at 5000rpm. It's on sale right now for $3425.95 complete from carb to oil pan. http://www.crateenginedepot.com. They also have the vortec heads ready to bolt on for $268.71 each. You can see all of the spec's and part numbers for that motor on the above site. My guess is that you could build the 383 stroker from the 350 h.o. spec's and maybe a little more cam and reach your goal! Check out the crate engine depot web-site. boatman
 
Wow now I am really getting some good ideas.. Thank you everyone..This forum is great! Well motor is out and on a stand..It is incredibly clean for a 1987 Always a fresh water motor! I may just keep it as a spare and buy a 383 short block and go from there!
icon_biggrin.gif
 
Hey what about a crateengine.com circle track 350 with 400hp...It pushes 400hp at 500rpm and redlines at 5800rpm. Under $5K
Just thinking???
 
wow
probably still need to change the head gaskets
the marine one's use a stainless shim and fire ring

what about that reman 383?
any dealers here make you a deal?

daren
 
It would be my guess, that come spring, cvx16's friend with the jet boat, may be looking for someone else to pick on! boatman
 
we just ran that 383 today... in a 30 yoa 24' sea ray... ran a mirage plus 19 @56mph gps.. a typhoon 19 4 blade @ 52mph gps... its a runner.. hell of a package with all the bells and whistles... drop by daren.. and see it its way cool
 
aint seen an alpha drive yet hold up over 300 hp.. <<< just my opinion... i've seen bravo 1s hold up with a professional driver as much as 800 hp.. and also seen the xr's crater at 400 hp.. w/o a pro driver.. just food for thought..
 
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