Getting More From my 21' Sunbird Eurosport slc2

[ae86custom]

So i have a 1989 Sunbird eurosport SLC II with omc sbc 350 and a omc king cobra outdrive. Ive had it for a year now and i think its time to do some upgrades. i have thru hull exhaust with a 14 1/4" 21 pitch ss prop and that is about the only mod done to it. I pulled it out for the first time this year and it ran great but the quadrajet carb is starting to act up. wont idle reliably and when i push it into the secondaries it bogs for a second and then goes. My top speed is only 42 MPH. Everytime i see one of these for sale people say they do almost 60MPH but i cant get anywhere close.

Instead of dealing with the quadrajet i was thinking about going with a nice after market carb from either holly or edlebrock with a different intake manifold and going to throw in a higher performance camshaft (anybody have some recommendations for camshaft selections, i do a little bit of tubing and wakeboarding but its pretty minimal.

I have also noticed that my trim fin or what ever its called on the outdrive has been erroded from electrolysis on one side and makes me think the prop isnt right for this boat.

 

[greenwell001]

Re: Getting More From my 21' Sunbird Eurosport slc2

nice boat....

how many rpms are you running at wot? seems like you should be running around 50 ish....i have a 5.7 merc on my 21 foot with side hull and a 20 pitch 4 blade ss prop running 4600 rpm at wot....i get about 56mph....is that 42mph on the speedo or on gps....speedos are not always completely accurate but doubt its off 10mph

 

[ae86custom]

Re: Getting More From my 21' Sunbird Eurosport slc2

nice boat....

how many rpms are you running at wot? seems like you should be running around 50 ish....i have a 5.7 merc on my 21 foot with side hull and a 20 pitch 4 blade ss prop running 4600 rpm at wot....i get about 56mph....is that 42mph on the speedo or on gps....speedos are not always completely accurate but doubt its off 10mph

Thanks, i only paid $5,500 for her.

Well i wont know until it gets sunny again. My Tach has never worked, the speed was on speedometer and i havent brought my new GPS out on the boat yet....First time this season was this weekend. I will find out this weekend hopefully. I know its 42 because the river i go on has a 40mph highway next to it and i can barely pull away from the cars.

I have a 14-3/4" 20 pitch prop that i am going to try next time out.

 

[ae86custom]

Re: Getting More From my 21' Sunbird Eurosport slc2

any recommendations on cam and carb setups??

 

[Bondo]

Re: Getting More From my 21' Sunbird Eurosport slc2

with omc sbc 350 and a omc king cobra outdrive.

Ayuh,... Fix what's Broke,+ Enjoy what ya Got...
Do a search on OMC,+ Especially, "King Cobra"...

Throwin' yer money at Hot Roddin' the motor won't be a wise financial decision...

 

[greenwell001]

Re: Getting More From my 21' Sunbird Eurosport slc2

i agree with bondo....when i first got my boat i want to do the same thing, dont worry about trying to make you boat go as fast as it can possibly go because you will end up spending the 5,500 dollars you paid for it twice over and maybe gain 6 mph unless you throw a big block in it, beleive me i know....just this year on somewhat normal maintenance i have spent 1000 dollars....some of the work i did and some i had to pay for.....this was in a three month period..new shift cables, new merc 4000 control, new impeller kit, carb rebuild and the list goes on...boats are very expensive to maintain so first of all get a manual on the motor and drive, get the carb kit and rebuild it, check the drive out thouroghly, and put the correct prop on it (and me personally, i would not run the boat at wot without the tack being fix and you cant properly prop the boat without know how many rpms you are running at wot) this forum has loads and i mean loads of great info so jump in and good luck

 

[ae86custom]

Re: Getting More From my 21' Sunbird Eurosport slc2

ya i was figuring on that, i knew omc's were bad after my bayliner but this boat had to much appeal to me. I was looking into repowering it but i need the cash first, i could get a fair chunk of change from the omc unit if i sold it from what i have found. The guy said there is only 650 hours on the boat. You can tell by the interior and paint that this boat stayed covered in a garage most of its life, and the guys dad was a marine mechanic and rebuilt the outdrive once already. Does the omc chevy bolt up to a merc outdrive, i have found some decent bravos around here for the $2k range.

 

[greenwell001]

Re: Getting More From my 21' Sunbird Eurosport slc2

whoa....hold up a sec...your boat seems pretty slick and with a LITTLE bit of tweeks you can get it where you want it. i dont think that merc will mate with omc and besides bravos are for big hp 300+....your 350 on a good day will make 230 and thats giving you some for the thru hull exhuast....hey i like to tweek on mine too dont get me wrong when i tell you that you need to slow down and use the boat a little more before you make some big changes...i can tell you that you can gain a mph or two with a 100$ investment on smart tabs sx....look em up. please dont think i am trying to rain on your parade but like i said i was in your shoes and i smartened up real quick when when the reality of time and money settled in...i paid 12,000 for mine and it was like yours, in wonderful condition...the things that i have done to mine were for speed and pleasure of use.....use yours a little more and you will see what you want....if you want speed sell it and buy a something in that range cuz you will put that much dough in yours anyway

 

[ae86custom]

Re: Getting More From my 21' Sunbird Eurosport slc2

whoa....hold up a sec...your boat seems pretty slick and with a LITTLE bit of tweeks you can get it where you want it. i dont think that merc will mate with omc and besides bravos are for big hp 300+....your 350 on a good day will make 230 and thats giving you some for the thru hull exhuast....hey i like to tweek on mine too dont get me wrong when i tell you that you need to slow down and use the boat a little more before you make some big changes...i can tell you that you can gain a mph or two with a 100$ investment on smart tabs sx....look em up. please dont think i am trying to rain on your parade but like i said i was in your shoes and i smartened up real quick when when the reality of time and money settled in...i paid 12,000 for mine and it was like yours, in wonderful condition...the things that i have done to mine were for speed and pleasure of use.....use yours a little more and you will see what you want....if you want speed sell it and buy a something in that range cuz you will put that much dough in yours anyway

This is why i posted these questions, constructive criticism , Seeing what you guys think about this kinda thing. Engines dont scare me, if i was going to swap the omc out i would be building my block to a 383 stroker with all the goodies, i know my way around engines and that was a partial influence of going to a bravo to make room for a built engine later. So to swap to a mercruiser power plant i would have to take the dive and repower the entire boat correct?

I have considered buying a scarab boat but i am going to wait until after i get my degree.

But from what i am starting to side with is just keep it till it gives me problems and sell and get my dream boat.

 

[concentric]

Re: Getting More From my 21' Sunbird Eurosport slc2

Hi
WOT rpm should be 4200-4600 and with gear ratio 1,41 and a 21 prop it will make at least 50-52 mph.

Check that you reach correct WOT rpm, and if not maybe overpropped- sorry.

If the Quadrajet i fiddled with, make sure you have the original spec for all components. The bogging going into secondaries was om my OMC 5,7l Cobra caused by to loose preload on the spring on the butterflie valves.

check out these links, the best on the net explaineing the Qjet

http://www.florida4x4.com/tech/quadrajet/qtune.pdf
http://www.florida4x4.com/tech/quadrajet/qjtshoot.pdf

 

[tschmidty]

Re: Getting More From my 21' Sunbird Eurosport slc2

The quadrajat can be a great carb really so I would stick with trying to rebuild it rather than dropping $ on a new carb. Lots of good resources like the one quoted above. Bogging can be really common on the qjet because of the size of the secondaries and a simple adjustment on the preload spring can make a big difference.

As far as speed, fix your tach and bring your gps out and then see where you are at.

 

[ae86custom]

Re: Getting More From my 21' Sunbird Eurosport slc2

alright ladies and gentlemen, i have returned from the dead. updates on the boat. I hit a rock last year with the drive, had insurance on the boat and they ended up buying me a new outdrive, but i know cobras are ****, my old out drive (what is left of it) is sitting in the corner of my shop in pieces, insurance mailed me a $3100 check and i figured i would go a different route with the new funds (and being laid off and being a boat addict) pocketed the cash, skeptical i bought a sei conversion kit from omc to mercruiser alpha one BEST SWAP EVER!!!! but didnt have the coin to buy a drive so i borrowed my roomates off his broken sea-ray v6 4.3l boat. Upside is she got back on the water last season. downside is i can only do 35mph and high rpm. well im happy to say i now have the cash to buy a v8 gear ratio drive and going to be aiming for my 50-60 mph mark. HIGHLY recommend the swap some beer and a night in the shop we managed to figure her out. only took some cussing and a new controller and shift cables, i will keep you guys updated on the progress. But if you are considering dumping your omc cobra and going for the mercruiser DO IT. better propeller selection and cheaper parts. have had 1-1/2 seasons on the conversion kit and she is running great (knock on wood). ordering my brand new SEI drive monday

 

[ae86custom]

Re: Getting More From my 21' Sunbird Eurosport slc2

and if anybody has questions about doing their own sei swap hit me up, always glad to help the boating community