To go with more power or not?

[SC-Speedy]

I have just bought an 84 Diplomat I/O that has a 185 v6 and the recomended power range for the boat is 140hp to 188hp my question is if i wanted to go to a small block 350 would it cause damage to the boat scince it is already at its top recomended hp? I have seen on youtube where people have put a 383 stroker in a Diplomat and was running 80 plus mph.

 

[Big Red]

STICK A SMALL BLOCK IN THEIR YOU WILL BE FINE.

 

[yellowfiero88]

I would agree with BR. A small block 350 will make you smile every time you hit it! I am going through a lot of the rigging now on my enchanter and reaching big (for boat size) speed takes lots of money. Not just in the motor setup, but also in the rigging to make it safe. Nothing worse than making the news with your mate on "high speed accident".

 

[hotdaddy27]

To go with more power, or not to go with more power.....what a stupid question!

Just kidding. I like the stroker idea myself.

Good luck.

HD

 

[sim]

Remember that old billboard, "Speed Kills"?
You're on the wrong website if you think anybody is going to advise you anything other that to Go For It!
Have at it, man.

 

[wca_tim]

I put a v6 in my 88 first, then decided that I wanted it to go a little faster... so went with a 383... just put boat back together and got on the water this past weekend after upgrading heads, carb, etc... and painting / "restoring" the outside of the hull... also pulled engine and replaced rear motor mounts as well a number of other "minor" changes / upgrades.

Yesterday evening we were running 5500 rpms with a 23" laser 2 and a 1.32 gear ratio with throttle left to go. full boat, full gas tank, tools, etc... with the slip numbers I've historically seen for this hull that's well over 80. it felt like we were flying and like the hull was finally at the point where it was almost all the way on the pad. we'll see for sure after I optimize the timing, get the jetting dialed in on the carb, put tabs back on it, put a little bigger wheel on, etc...

Horsepower is like sex - too much is never enough...

 

[Gimme Fuel]

go for it....anything stock sucks. Don't you just love the advice you recieve on here? haha

 

[wca_tim]

you can now get just about everything to put an ls series engine in it....

 

[Gimme Fuel]

I have a local guy here who builds some wicked LS series motors on the side and is awesome with tuning and fuel injection set-ups. We took engine design together in college and he even has his own dyno.

 

[wca_tim]

many times when I stand on the corvette hard, I'm struck by the broad torque curve and the way it just keeps pulling from almost off idle to 6000 rpms (in almost any gear all the way to about 190), its obvious what a great marine engine it would make.. and light too (it's a modified ls1). a marine designed ls7 build with closed cooling would be a good bit lighter than a regular chevy small block and make well over 2x the torque and horsepower... all day long...

I also love the degree of sophistocation in the engine control system in the car, and although that part would not be easily marinized that I know of - I get 30 mpg on the highway and about 20 in town when I drive like an old man even when being a little more "spirited" the average in town only drops to about 17... sure a boat just takes more fuel to move throug the water, but having the balls there when needed and good fuel economy would be a really nice thing...

 

[SC-Speedy]

I kinda like the LS motor idea

I apreciate all of the advice I like the LS motor idea but your talking about doing a whole lot of work and upgrading from alphaout drive to a bravo if you go over 350hp then you got more weight from the bravo bravo setup. I think I am probably going to do a 350cid 300hp then I can keep the alpha equipment and we arent talking about ten grand for the bravo setup. Anyway Thanks for the advice.

 

[jazzy]

i love the ls motors i think theyre great for cars but i dont know about in a boat just doesnt seem like they would hold up all aluminum motors high compression i dont know where you guys boat but its always rough here and im always on and off of the gas hard in each direction but man that motor screams i have a new camaro and love the power of it i wish it spun another 1500 rpms it feels like you have to shift too soon that can all be corrected but im gonna wait till the warranty is done

 

[wca_tim]

I was really sort of kidding about doing an LS series engine - you're talking big dollars for a marine build... and they do make great marine engines...

I hear you on the shifting thing... my corvette has the close ratioo 6 speed and a 4.10 rear end gear, lowered, full high flow exhaust (corsa), top end engine mods, reprogrammed ecm, ls7 clutch and pressure plate, upgraded torque tube assembly, drilled slotted rotors, etc, etc, etc.... with cold street tires and the active handling turned off, the tires will break loose anywhere in the first four gears... with hot, sticky tires, it's a blast to drive, handles like it's on rails and still rides like a caddy for what it is... sorry, by far my favorite of all the cars I've owned. although I've not had a new camaro... that's an awesome car..

back to the op... Don't be too worried about the alpha drive thing with your light boat. also, use the original gear ratio, the boat will be faster. Note that I'm probably pushing around 450 horsepower through mine. running an alpha ss right now, but have had a couple differenmt alpha drives on it and they've held up VERY well. I'm finding the vredline shockproof lube is by far the best...

I'm pretty sure I'm going to be deep into the 80s by the time I get it tuned this time... and still have nice manners.

 

[mkhammer]

Here's some v-6 power for you, it runs like a built 350. had to put some forged pistons and some better valves in it,

 

[Gimme Fuel]

When I took engine design in college, one of our instructers had a 35 Skater with twin LS7's in it. These motors were a work of art. Dry Sump oiling, all aluminum, FAST tuned EFI....you name it, these things had it. 750 HP on dyno each. Absolutely wicked small blocks.....with an absolutely rediculous price I'm sure.

 

[Lakeside Restorations]

I think a nice SB would run nice in there.. We have had really good results with repowers & the new SB stuff..

Jamie / Lakesidee

 

[SC-Speedy]

Just got my hands on a 6.0 vortec!!!

I just got my hands on a 6.0 vortec from a Chevy 2500hd for $800.00!!! the truck was trashed but it would still start and run like new i think this would be a great start to a motor for my diplomat what do yall think? PS. 23000 miles on it and I got the computer and wire harness. Where can i get parts to set it up for marine use? I would like to keep the motor as stock as possible for reliability i would like a play all day setup.

 

[Minor Threat]

The alpha drive will hold up to some serious HP if you watch what your doin. I have a temp gauge on the drive as well as a drive shower. Im also running a 383 stroker with blower. Goland engines in Hudson, NH built my set up and says its about 575HP. I have the alpha ss drive and it has held up. Just no whole shots. Also no long excessive runs at W.O.T. I back off when i see the temp gauge hit 220.

 

[Lakeside Restorations]

I just got my hands on a 6.0 vortec from a Chevy 2500hd for $800.00!!! the truck was trashed but it would still start and run like new i think this would be a great start to a motor for my diplomat what do yall think? PS. 23000 miles on it and I got the computer and wire harness. Where can i get parts to set it up for marine use? I would like to keep the motor as stock as possible for reliability i would like a play all day setup.

You wont be able to use the wire harness or ECM from the truck. You will need to adapt it to a marine ECM for starters.