How Much HP?????

bigdog347 · **Joined:** Mon Jul 28, 2014 11:10 am **Posts:** 12

Guys I'm new to I/O boating. I recently purchased a 19ft horizon with a sized 5.0 ford. I just pulled it out and I'm in the process of tear down and rebuild. I'm going to add some of my small block ford fun parts and hoping to get up around 340-360 HP.

Will the stock outdrive handle almost double what the stock engine puts out?

are there upgrades to the outdrive that will allow it to handle this power?

also if the 5.0l is unusable I will be using my Built 5.8l that would be around 400HP with more torque than the 5.0L

What are your thoughts on this?

meinmelb · **Posted:** Sun Aug 10, 2014 12:30 am

What Drive do you have?

deafwish · **Posted:** Sun Aug 10, 2014 12:35 am

What fun parts do you plan on fitting?

ric · **Posted:** Sun Aug 10, 2014 6:29 am

If it's a Volvo or a Alpha, sure.. just don't punch it from a stand still. Ease into it slowly.

TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

If its a Volvo or Merc Bravo you will be OK. The alpha will not handle it and is more of a lightweight drive system. The alpha is good within oem specs.....some try to help it along by installing drive showers to keep it cooled down since the alpha will run hot under load for extended periods of time.

I had beefed up a 5.7 with the alpha drive....it blew the gears out of the lower unit casing. Since then I learned to go with OEM specs. The old man advice is to rebuild her within specs and have less headache. My bud drag races and has also learned to overbuild then step it down...pushing it to the limit will make you sad and empty the wallet. I will add that no matter what you do, you will not have the fastest baddest boat on the water.

bigdog347 · **Joined:** Mon Jul 28, 2014 11:10 am **Posts:** 12

How silly of me. it is an OMC outdrive but from what I've been told it was when Volvo had just acquired OMC (1995) so it has Volvo parts (it looks like a penta drive). the other thing that makes me think its a Volvo drive is the shifter in the drive, mine is a cable with a lock nut, not the shift fork style I see with other OMC drives. as you can see I'm still trying to figure out what I have.

Also just wanted to give you an update I just tore down the 5.0 and found it full of water in the oil pan, the cylinders and exhaust manifolds and two spun rod bearings. due to the machining needed to build the 5.0, I think I'm going to use my 5.8 short block that is ready to go. I have an intake that will work, all I need is a distributor for this application.

For fun parts I plan on using GT 40 X heads 64cc with 2.02intake and 1.60ext valves, the block was zero decked so I should be in the 10-10.5 cr zone (93 octane friendly)The cam I haven't decided..... I was thinking cause engine vacuum is a none issue (in a boat) I might go with something with lope. this would put the power band in the 1500-6500range would the drive be able to handle the RPM?

I'm defiantly going with through hull exhaust (I love the sound).

TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

If you can post a pic of the drive I'm sure you will have your answer real quick like. I'm no guru (remember glowed up drive back in 1980s) but I'm not thinking you want too much lope.

ric · **Posted:** Sun Aug 10, 2014 8:57 pm

There's plenty of people with 400+ hp with Alphas having no issues. Just go read any go-fast forum. The secret is to just not floor it off idle. Once you're moving on plane it's fine.

deafwish · **Posted:** Sun Aug 10, 2014 9:16 pm

Do you plan on using the boat in salt/ brackish water?
Alloy heads and intakes may not last long without closed cooling - even in fresh water!
Loping cams + wet exhausts = hydrolock.

rpengr · **Posted:** Sun Aug 10, 2014 9:16 pm

I would think you would want to select a prop pitch that would max out at around 5500 rpm, and have a decent cruise speed around 3500 rpm where you will spend much of your time. Unless you are designing to be purpose built for drag racing, in which case a Four Winns is the wrong choice of hull.

Also, keep in mind that I/O's are horsepower rated "at the prop". Since there is a 10-15% loss through the gear train, your 400 HP build might be equivalent to a 350HP rated I/O. And the higher the RPM, the greater the loss in the gear train.

Most of the users on this forum are conservative boaters who would like their engines to last 1500-3000 hours in the tough marine environment. This is a far different goal then building a street mod engine. If you want the engine to last, you will want to understand the unique requirements of a marine build.

deafwish · **Posted:** Sun Aug 10, 2014 9:27 pm

I seem to recall the SX Cobra drives were rated to around 5000RPM.
I have a 1997 model SX Cobra (transition model from OMC to VP) and it is as strong as an ox.

bigdog347 · **Joined:** Mon Jul 28, 2014 11:10 am **Posts:** 12

I be clear I value you guys opinions because I'm new to boating so I lack the experience you have. I'm glad I asked you guys about my plans because I didn't even think about the water going back up the exhaust during the valve overlap. As far as the use it will be a fresh water boat and I'm not going to be drag racing but when I go out on the lake I want big block boats to be scared. I feel if I can get my small block up to the same HP as a stock 7.4 I'll have the advantage because the small block weighs less. I have always been a hot rod guy, as you may have noticed from my user name I've built some Mean small block fords. I hope to build a fast reliable long lasting boat.

Again Thank you.

P.S I'll try to get photos of the outdrive soon.

NiagaraChillin · **Posted:** Sun Aug 10, 2014 11:27 pm

In addition to what others have said, also be aware that there ARE certain "marine rated" parts that have to be on a boat engine, starter, alternator, carb. Basically anything that makes a spark or delivers fuel. This will keep you from going boom. As far as what drive you have, if it is a 95', chances are it is a Volvo. Does it say SX Cobra on the sides? If so, it is a Volvo.

ric · **Posted:** Mon Aug 11, 2014 6:40 am

A "go fast" boat just blew up at my marina last month and put 2 people in the hospital. It was all automotive parts: ignition, carb, alternator, etc.

It's not some stupid law made up by a politician. No automotive electrical parts!!!

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

Depending on where you are, you can defy the heck out of the game warden / boat police with loud exhaust all you want; he'll still write you a ticket if it's too loud.
I think you're on the right track for sure, and can build power with a small block. Just remember though that as others have written here, they won't last as long. There's a reason they put big blocks in the bilge to go over a certain amount of power... they'll do it all day long and barely break a sweat.

www.iFourWinns.com

How Much HP?????

Who is online