Can the omc 800 take 290 hp?

[fabrimacator21]

Boat weighs about 3500 and I'm planning on a 23 pitch prop.

I've done some searching on here and I keep reading bad things about the 800 series omc I/O's so I want to make sure my I/O can handle it before I bolt a more powerful motor to her.

I currently have a 200hp omc 305 which does the job nicely but I'd like to get to upper 50's and maybe low 60's.

Is it doable or will I end up stranded?

(EDIT: hp will be around 280-290.... not 350. Disregard the dyno sheets)

 

[JustJason]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

Kabooom!!!

 

[mtbr00x]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

I started to reply before I read the HP part of the title but my OMC 800 has a gm 5.7 350. I think it has 280 HP but not exactly sure.

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

Kabooom!!!

Is that experience or a guess?

 

[Bondo]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

Ayuh,... The 800 Stringers were marginal at Best,...

Keepin' 'em Running is a Full time Hobby.....
Hot Roddin' 1 ain't gonna have a Pretty out-come....

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

Ok so the general consensus is don't do it?

I'm suprised to hear the omc 800 was such a turd... my dad had one on his centurion and it never let us down in 15 years of boating... even hit ground at 40 mph. Punched a whole in the lower half but after he tig welded it up it was fine.


What exactly are the notorius spots on em? I'm just worried about gear crunching...

Anyone have experience with 300+ hp and the 800 series?

I just ran the numbers through desktop dyno and it's looking like 317hp at 4500. If I were to take off easy and keep the rpms under 5k (the 800 series overheats at 5k and up) shouldn't it be ok?

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

heres the desktop dyno numbers on the motor

317 hp at 4500 and 398 ft lbs at 4000.

The only thing I'm worried about is will the outdrive be able to take that power with a 23 pitch prop and a 3500 lb boat.... I have trim so the take offs won't be much stress.


Heres why I think it can take it....

The take off is the most stress on a motor/outdrive. Take off rpm is somewhere from 1000-1500 rpm.... at that rpm the estimated power is right around 300 ft lbs and maybe 20 more hp then a 260hp 350 has.

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

I started to reply before I read the HP part of the title but my OMC 800 has a gm 5.7 350. I think it has 280 HP but not exactly sure.

How long have you been running that motor? Can you give me the specs so I can run it through desktop dyno and figure out the hp/tq?

 

[n2ostroker]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

Are you using the 305? What is being done to it? I think your numbers might be a little optimistic. That and a 3500lb boat with a 305 and a 23p prop isn't going to work out too well. I wouldn't think about pushing an outdrive isn't made anymore anyway. If you break it you'll have a nice expensive fix on your hands. It may last, may not. I don't think with boat rpms and a 305 you'll have any problems but who knows.

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

It's a 355....


My current motor is a stock 200 hp 305. I've heard of people running 350's with the 800, like mtbr00x. 280 hp. Doesn't seem unreasonable since most of the extra power is up top which doesn't stress gears nearly as much as take off/getting on plain. Most of the down low numbers are only 20 more (ft lbs and tq) then a stock 260 hp Omc 350.

I REALLY want to put this thing in my boat but I don't want a 2k dollar I/O bill either.

Can someone school on the 800? What fails? Is it because of too much power or something else?

I have read that you can't spin them over 5k because of oil overheating. As long as I keep it at 4500 shouldn't it be ok?

Sorry for all the questions but I'll be pulling this motor out of my truck in a few weeks and need to know what to do with it.

 

[n2ostroker]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

You may never have a problem. But when/if you do it'll be expensive. You seem to be fairly set on doing it though. I just rather replace the drive now with a better unit or not do the mods rather than seek approval only to have it break later.
I run a 355 9:75 comp, heavily ported heads, performer rpm intake, Edelbrock 750 carb and the Comp xm262h cam. I run it in an 18' hull that is pretty light(3000-3200 lbs loaded). I also run a 23p prop and turn right around 5k rpms running low 60's. Hell I'm afraid of hurting my alpha. There is plenty of stress on the drive at the higher rpms as well. Drag is what causes the motor to have a natural rev limiter in a boat.

I also have a Bayliner 2450(3700lb unloaded) that had a stringer drive on it. Note: had an OMC. Previous owner replaced 3 of them after switching to a 350 before yanking the whole thing and putting a Mercruiser/Alpha one set up in it and haven't had a problem in 3 yrs.

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

That is just about the exact same motor I want to run. Same cam except my comp ratio is 10:1.

I am not set on doing the swap so much as WANTING to do it. I can't afford a 2k I/O bill... if I have to pay 2k for an I/O that'll pretty much be the end of my boat.

That being said I ran the desktop dyno numbers using dart iron eagle heads flow numbers.... the heads I will be running are camel hump chevy heads from the 350 hp 327's. So Most likely I'm looking at more around 290-300 hp.

Sounds like theres no definite answer though. kInd of a trial an error thing and I can't afford to be the error so I need to really nail down the limits of my I/O. I'll call a few dealerships and boat mechanics tomorrow and see if I can find any answers.

With the 355 I'm hoping for 60 but expecting more like high fifties.


What could I expect to pay for a beefier I/O? What do you recomend?

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

Scratch the 350 hp.... it'll be more like 280-290. Should that be reasonable?

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

ttt

 

[mkast]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

I'm suprised to hear the omc 800 was such a turd... my dad had one on his centurion and it never let us down in 15 years of boating... even hit ground at 40 mph. Punched a whole in the lower half but after he tig welded it up it was fine.

Anyone have experience with 300+ hp and the 800 series?

I'm going out on a limb on this but, it lasted 15 years because your dad didn't bump the horsepower up. Bolt the engine in, when the drive takes a dump, then, you can say, from experience, "I wouldn't do that."

 

[fabrimacator21]

Re: Can the omc 800 take 350 hp?

Re: Can the omc 800 take 350 hp?

I'm going out on a limb on this but, it lasted 15 years because your dad didn't bump the horsepower up. Bolt the engine in, when the drive takes a dump, then, you can say, from experience, "I wouldn't do that."

Thats why I'm asking in here.... I don't want to be that guy.