Powerboat Forums at SpeedWake banner

Adding turbo/supercharger to OMC 3.0l

24K views 30 replies 9 participants last post by  DonMan 
#1 ·
Ok, this is serious. Stop laughing.STOP LAUGHING!! Ok, now lets continue.

I have a 1989 Bayliner Capri 19' Euro style with a OMC Cobra 3.0l 140hp. I LOVE my boat so no I wont just "get rid of it and buy a better one" as the lines are what sold me. Its not as fast as I want, so I was on another forum and someone made a comment of doing a supercharger or turbo. Got me thinking..NEVER a good thing!

I would LOVE around 200hp which is about a 40% increaese which isnt the easiest I know but it could be doable with a power adder. I was told my OMC outdrive could take a SB engine so 200hp should be ok, in theory. Plus I know turbos are easier on engines.

Now my intake/header are the same log and it connects to a flex connector for the exhaust. I was thinking if I had something made to attach to the exhaust side that the turbo can mount to, then a tube bent back to a box that the carb sits on (maybe go from 2 barrel I have now to a 4 barrel) that blows the air in, seems like this is the easiest as I can use the stock carb setup..if i put the turbo on top of the carb I run into fuel problems. I mean doesnt sound like too much trouble..if I only run 5-6 pounds of boost I wouldnt need an intercooler (air-water ones run $500+ it seems) and will pump lots of fresh air to it.

So thoughts..and be serious dont just flame me please. I build import bikes and cars, so I am use to wrenching, just not on boats. I have researched a ton but cant find info like what would I expect from a boat with 5-6 pounds of boost..should I run a blowoff to be safe (I will run an adjustable boost controller).etc.

I am building a 25' powerboat with a big engine..I just love this boat and like being different..as you can see!! Thanks for the help folks! :D
 
See less See more
#4 ·
hello codygrizz, I'm new here also so I'll assume you are serious so here is a serious reply.
Your theory on a turbo setup won't work, you can't just blow into the manifold and sit the carb on a box, set up like that the engine won't even start. You either have to blow through the carb or suck through the carb but you can't just blow into the manifold. I'm not saying don't do it! I'm saying do a bit of research and visit a few turbo installers to discuss your requirements.
140hp 3.0 OMC in a 89 Bayliner suggests that it’s also a small case Cobra drive, if I’m right than I have some bad news I'm afraid that drive is not going handle the extra power your looking for and upgrade parts are not available. They are an economy drive designed for low hp installations. I suggest you look around for a Volvo 270 - 280 as these came with the 3.0 and are very strong and will handle anything that 3.0 can dish up.
I must admit my first reaction to your post was to say don't do it! but I'm pretty sure you don't want hear that so I won't say it............. so I'll think it out loud, don't do it. Re power your pride and joy with a SBC and Volvo 270 - 280 and you will have a blast with a safe reliable boat that will serve you well for many years and still provide you with the satisfaction of doing the upgrade yourself.

Cheers
 
#6 ·
Yes the standard Cobra will handle the SBC no problem, some tricky set up issues to be aware of but I'm assuming this is the 400 series drive in your 89 Bayliner. These are different from the V6 and V8 drives. You may be lucky if it’s a 1990 3.0 it may be the bigger lower unit but I think you will find yours is the 400 series so I stand by my comments re the lack of strength of these drives. Give us a model or serial number to be sure.

Cheers
 
#7 ·
Thanks for the reply. And the only answers I want to hear per say are real ones from folks with knowledge, which I think I got. Where are my serial numbers located as I tried finding them but couldnt. Once I find that out I will post them.

Sprry about the general turbo install talk..I was just throwing out a simple version for people. I build performance import bikes and cars, and do turbo work, so know it will be a bit harder than my post but it actually wouldnt be as hard as most cars due to the engines layout..I would compare it to doing the bikes if there are no kits out for them. Only reason I was thinking turbo was lighter than a SB and easier on the drive generally.

Now the Volvo drive..I would THINK it would be a bit cheaper than a Mercruiser Alpha/Bravo..no? And how much HP could one of them take? I would be very happy at 200-210, I think that would allow for the extra SB engine weight and still have a bit more "umph" than now, but dont want to be pushing the design on the edge. Any of yall thrown power at one?

Thanks again for the replys..good to see good folks with real answers..great forum!!
 
#8 ·
another idea would be to look for a Mercruiser 470-490 engine. The only work would be adapting the mounts I think.
That is also a 4 cylinder except it made 170 to 190hp (depnding on year and carb) and may be more in line with your thinking. Its a horse of a 4cyl :)
I have even seen them used in rat rods with reground cams and headers they make even more power.

right now there are 3 Mercruiser 470 4cyl engines on ebay for under $500 ..
 
#9 ·
That would be real nice..almost the power I want with the same weight about. Ad a cam and maybe a different carb, maybe I can hit that 190-200 mark. Will my OMC400 hold it though? Or would I need to go with the other outdrive?

THIS is why I love this site..people who actually have answers! I asked this at another big boat forums and all they ever say is "sell it" and crap, they dont see people might actually LIKE their boats..just want a bit more power! :clown:
 
#10 · (Edited)
since its still a 4cyl it wont be making gobs of torque like a V8 so I imagine your drive will be allright,,all depends on your brand of driving. I have a 454 on my Alpha drive and its doing just fine but I dont beat the crapout of it either.

The merc big 4cyl was a great little engine. A good freind in the 80s had a Nova 21 with two of the 170 versions and that thing would run with the big single V8 Novas of the day and waste half the fuel doing it. There was one just like it on ebay a few months back. Kind of cool having dual motors on such a small boat. My cousin right now is rebuilding an old 70s 17ft Formula with a 190hp version, its a very light boat and ran 52mph gps befopre he took it apart to rebuild it.
I think the 190hp version has a 4bbl while the 170hp has a 2bbl if I remember right. Believe it or not there was a company way back in the day (mid80s?) that made a turbo kit for these engines. I think it was 200hp for the 2bbl and 220hp for the 4bbl version. It was very low boost maybe 3psi. These engines use the Ford 460 cylinder head .
 
#11 ·
I am an easy driver..I dont go from stop to WOT in one motion like some..I throttle it like you need for pulling a skier out of the water..light to medium..then full.

That would be a fun little scoot..dual 170s! I am building a 21' boat next year, be fun to see 2 190-200hp engines on it..like you said, all the fun, half the gas!

Thanks AGAIN for the response!
 
#13 ·
I'm still worried about that 400 drive but I'll leave you to decide what you do with that. Re the Volvo, yes I run a 270T behind a 351 Cleveland in a ski boat that’s putting out around 350hp and has been for many years now, the drive is my fav part of the boat. On the 2nd hand market they are around the same bucks as the alfa and much cheaper than the bravo. Only issue with the volvo is there is not much around re Hi-performance props. and the drives with power trim are getting hard to find. Oh and BTW, I think I also said 'don't do it' or maybe I was just thinking out loud. Lol. Anyway regardless of the route you take modified head and cam or a turbo I think you’re still a long way from seeing that 200ho without a full rebuild. I also think throwing money and time at that little engine will most likely leave you disappointed with the end result. My advice re the whole project would be to sell it and buy a more powerful boat but if you’re that keen to do this than go for it……..
 
#15 ·
Thanks. Maybe I will see if I cant sell off my package to offset another package with the Volvo and SB engine. I really dont want to sell it as I DO love this boat just wish it had more power. What should I expect to get out of my setup? The outdrive had new seals put in it by the Marina I purchased it from a year ago, and the engine is the 140hp and will have a new carb and electronic ignition conversion with everything there from throttle to prop.
 
#19 ·
CodyGrizz said:
Thanks. Maybe I will see if I cant sell off my package to offset another package with the Volvo and SB engine. I really dont want to sell it as I DO love this boat just wish it had more power. What should I expect to get out of my setup? The outdrive had new seals put in it by the Marina I purchased it from a year ago, and the engine is the 140hp and will have a new carb and electronic ignition conversion with everything there from throttle to prop.
with a 260 HP 350 I would expect about 10 mph gain

Rule of theumb is 10-15 hp per MPH

Your 2 variables are your adding weight,,,

but the boat is small and light.

Should be an easy project.

The only part will be aligning the front mounts as they are different with teh I-4
 
#20 · (Edited)
that rule of thumb though isnt very accurate when you dont consider torque.
I picked up 5mph (dont even have the right prop yet) going from a 300hp/350 to a 310hp/454 .. Rule of thumb would say I should have picked up zero mph,, 100 extra foot pounds of torque say otherwise.. At the same rpm it can swing a prop thats 3p size bigger.
Going from a 4cyl to 350 he will probably pick up 200-250ft pounds of torque,Id say his boat would pickup at least 15 probably close to 20mph with the right prop.
Im guessing it runs 35-38 now. That light 19ft Capri with 260-300hp should run darn near 60mph. Dont know how long the hull/transom/stringers will last though.. :)
 
#21 ·
With me and 1 other person I run about 40mph..not too shabby. It is a light boat I guess. The new boat layout will bring weight more center than back, so that should help it a bit. I think I am running a 19 prop, looking at one at West Marine that has an adjustable pitch, so I can have a few options. I mean I would LOVE to hit 45-50 and not be at WOT, I think the hull can take it. Least I HOPE so!!
 
#22 ·
I`ve been reading this thread and didn`t want to interject my opinion, because you were only looking for answers from "people that know". I`m no turbocharger expert, but I can tell you that you will have mucho fabrication, a lot of $$$ and countless hours into this project for very minimal gains.
Quit dicking around with that gutless 4 banger and drop a bone stock, reliable 350 in there and be done.

FYI --- I`ve never heard of anyone who had good results from those adjustable pitch props....

Just my .02

Good luck with whatever you do. :)
 
#23 ·
Thanks for the reply.

Now when I said an adjustable pitch prop I do NOT mean the one that sets its self. This one is West marine and you adjust and lock in the pitch you want. I seen ones that adjust as the boat moves and heard mixed reports on them. This one is nice in you can replace the tabs as needed, which would be great. Buf if they dont work, it would be a waste.

Could you explain why they wouldnt work? I thought pitch was pitch. or is it to do with the cupping of the prop or what?
 
#24 ·
CodyGrizz said:
Could you explain why they wouldnt work? I thought pitch was pitch. or is it to do with the cupping of the prop or what?
I`m no prop expert either ( Gee, do I know anything...??? :confused: ).

If a propellor blade is not permanently fixed, I can`t see that it would be efficient. Once you reach a certain performance level, that prop will not work at all.
 
#26 ·
Don't be so quick to get rid of that 3.0. as some of you old car guys know this is the old chevy/pontiac "Iron Duke" engine which is very reliable and strong. there are performance accesorys for this engine. use to be in the GM performance catalog under pontiac. heads,cams, 4bbl intakes etc. They use to use them in some racing classes don't know if they still do? I had a stingray with a 3.0 that I thought of doing a turbo swap on but sold the boat due to the fact that it was getting too small for the family :( . now i'm into another project, but any way do some research these motors do very well in small boats. I got mine doing 50 with no major mods, with a stock alpha. Interested to know how you make out good luck :)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top