More power from a 4.3L - HELP!

[DonziDan16]

Right now I have a 1990 Sweet 16 with a 4.3l OMC, 2bbl, 175 horses. She tops out at 51 @ 4200-4300rpm on a 22 pitch prop. I'd like to go a few mph faster, nothing too radical. Hoping to hit 55.
I was wondering if I could do this with an Edelbrock intake, 4bbl carb, and K&N flame arrestor. Any idea where that would put me? Also wondering about some lightweight/underdrive pulleys?
Should I try moving down to a 21 pitch prop?
I don't want to swap for a 350 and I don't want to machine anything or get into internals. Just some bolt on stuff.

[smokediver]

just a few mph .. ok ... lol .... if it were me and i was looking for just a few , i think i would mess around with props ... try dropping down to a 21 in the same style prop and if you are about 300 rpm's short of max rpm .. send it in and get it lab finished .. there is your couple of mph right there ... cheap speed ... in comparison anyway ...

[Pismo]

Put on a 4bbl carb.

[ky-donzi]

I would think that the 4-bl would help, but don't know how much cam you have now so the increase might not be much. The other day I saw this on ebay. I would imagne it would be a hugh increase. good price too!

http://cgi.ebay.com/ebaymotors/91-1991-CHEVY-4-3-WHIPPLE-SUPERCHARGER-S10-ENGINE-S15_W0QQcmdZViewItemQQcategoryZ33741QQihZ010QQitem Z200194997754QQrdZ1QQsspagenameZWDVW

[The Hedgehog]

Yes, you can. The OMC exhaust is actually not bad. I did lose mine for weight and asthetic purposes. I also did a through hull which is a trick on a 1990 OMC.

I got 60 out of mine but did the cam and heads. I don't think that I picked up too much from the expensive head work but I did that was so it will like the procharger that I will put on when not juggling too many things.

You will not really get anything out of the filter. You will need to do it though as big carbs on a V-6 run rich. I suggest a gaffrig. I tried a number of others. It ran the leanest and had the best fit/finish.

One thing to watch out is the carb. First of al, people tend to overcarb. I did. If you get a 600 CFM edelbrock you will have to jet it down. They make a kit for that. You will still need to go down a couple of sizes in jet. I was not too worried there since I will use another carb later when I do the blower. It ran much better after re-jetting.

Holley makes a nice smaller 4 bbl which actually a better carb. I have one laying around. If you use one of those you will have to modify the thermostat housing. I am sure that someone has a smaller housing that will work. Carbs with bowls in the front and back are hard to fit on a v-6. Do some homework there and you can make it work.

I would not waste any time of work on the pulleys unless you are going after bling. You could probably put on a cross over, lose the water pump and pick up 5-10 hp. That won't really do much.

If you only want 4-5 mph a 4 bbl is the way to go. It really wakes it up.

I have some pics of mine around somewhere. I have posted them on the site. They can probably be found easily with a search.

Don't worry about the prop until you have the rest done.

[MOP]

That Whipple kit is some nice! You could bolt it on a 4.3 or put it on 350 and spool it up a bit. Man that is a tempting morsel!

[glashole]

how long have you had the boat?

get it out in some chop and let er rip :smash:

you should get 55mph

[DonziDan16]

Thanks everyone for the quick replies.

That whipple kit looks awesome. I'm not looking for anything that serious though. Maybe sometime down the road.:wink:

Big Green- What kind of exhaust do you have? I haven't been able to find anything for OMC. I was considering the Holley 400 instead of the Edelbrock 600. My dad tried putting a Holley 600 on his boat which has an Edelbrock intake and it wouldn't fit properly- there was stuff in the way. I was afraid I might run into the same sort of problem. Maybe it was just the way he had things set up though.

Glashole-
I've had the boat for almost 2 years now. Even though it's a 90, it looks great. And the motor was rebuilt by Jasper right before I got it. I've opened her up in chop and trimmed it to the sky but 51 is all i can get. :(

[The Hedgehog]

Thanks everyone for the quick replies.

That whipple kit looks awesome. I'm not looking for anything that serious though. Maybe sometime down the road.:wink:

Big Green- What kind of exhaust do you have? I haven't been able to find anything for OMC. I was considering the Holley 400 instead of the Edelbrock 600. My dad tried putting a Holley 600 on his boat which has an Edelbrock intake and it wouldn't fit properly- there was stuff in the way. I was afraid I might run into the same sort of problem. Maybe it was just the way he had things set up though.

Glashole-
I've had the boat for almost 2 years now. Even though it's a 90, it looks great. And the motor was rebuilt by Jasper right before I got it. I've opened her up in chop and trimmed it to the sky but 51 is all i can get. :(

I have the IMCO Thumper setup. I put it on a 1990 OMC like yours. It has polished risers and looks great. Like I said, I took them through hull. I had to have a bend put in one of my tips on the inside to clear the steering. It was not a huge deal. I think I can find a pic of them if you can't find my posts with the engine. I also used the Edelbrock Performer manifold.

The Edelbrock carbs have bowls on the side and don't conflict with the short v-6. I think that they are retooled Q-jets.

My boat is now a combination of merc,OMC and aftermarket stuff. I punted the OMC ignition in favor of a electronic merc. I still have the drive and some other components. Edelbrock makes some pretty polished valve covers for the V-6.

[mikev]

I have an 88 merc 4.3 same engine came with a 2bbl carb. i did the edelbrock intake and carb with the 4.3 jet kit. i also did the plastic carb spacer. It made a big difference gave me about 400 more rpm's which is a couple MPH and alot more out of the hole and midrange punch. next i got my prop repitched up two inches to make up for the extra rpm's and lab finnished it. I got another 2 mph from that and didnt loose any of my bottom end punch. both were a great bang for the buck modifications. my boat is a 19' bowrider so a little different but i would do it again in a second. and i have a question where is a whipple kit for it the ones for the 4.3 i thought were discontinued.

[The Hedgehog]

I would say that you are looking at about the cheapest dollar per mph ratio out there! If I could drop $500 and pick up around 5 mph I would do it all day! $100 per mph, it does not get any better than that. Many of us get in the range of 10x that per mph!:hangum:

I would say that the next biggest bang for the buck would be that Whipple that Phil mentioned. Throw that on, tweak a few things and you will easily run in the 70's:eek!:

I would love to see that done to a v-6. Just don't beat me to it.

[DonziDan16]

I have an 88 merc 4.3 same engine came with a 2bbl carb. i did the edelbrock intake and carb with the 4.3 jet kit. i also did the plastic carb spacer. It made a big difference gave me about 400 more rpm's which is a couple MPH and alot more out of the hole and midrange punch. next i got my prop repitched up two inches to make up for the extra rpm's and lab finnished it. I got another 2 mph from that and didnt loose any of my bottom end punch. both were a great bang for the buck modifications. my boat is a 19' bowrider so a little different but i would do it again in a second. and i have a question where is a whipple kit for it the ones for the 4.3 i thought were discontinued.

I'm glad to head you had success. I'll definitely be doing these mods in the spring then. What kind of flame arrestor did you go with?

Big Green, It'd be great if you could send a link or post some pics. I couldn't find any through searches. About how much weight did you lose switching to the IMCOs? I have my eye on those valve covers too:biggrin.:

[The Hedgehog]

It is there but for some reason is not coming up in a search. If someone could tell me how to post a link to the post I will do it.

If not, PM me your e-mail address and I will send them to you. The sight will not let me re-post the pics.

[mikev]

went with a barbron 4" x 8" flame arrestor with two vent tube attachements for the valve covers. it was about 80 bucks cant rember where i ordered it from. that whipple charger wont work it is designed to bolt on a tbi manifold and the tbi bolts on the front of it. if you had a tbi fuel injected 4.3 I think they made them for a few years it would work. wont work with a carb though.

[RedDog]

... The sight will not let me re-post the pics.

Rename the picture and then re-upload. Or better - click on "User CP" in the left hand menu. Scroll down to "Attachments." Find the picture and click on the file name. Copy the URL address and paste it into your new post like: http://www.donzi.net/forums/attachment.php?attachmentid=1558&d=1080581508[/ img] (without the space between / & img)

[IMG]http://www.donzi.net/forums/attachment.php?attachmentid=1558&d=1080581508

[The Hedgehog]

Rename the picture and then re-upload. Or better - click on "User CP" in the left hand menu. Scroll down to "Attachments." Find the picture and click on the file name. Copy the URL address and paste it into your new post like: http://www.donzi.net/forums/attachment.php?attachmentid=1558&d=1080581508[/ img] (without the space between / & img)

[IMG]http://www.donzi.net/forums/attachment.php?attachmentid=1558&d=1080581508

I tried the rename earlier. The site is too smart for that. I will try the other.

[The Hedgehog]

Click on that

http://www.donzi.net/forums/attachment.php?attachmentid=29316&d=1180793637


or that

http://www.donzi.net/forums/attachment.php?attachmentid=29315&d=1180793637

[DonziDan16]

Click on that

http://www.donzi.net/forums/attachment.php?attachmentid=29316&d=1180793637


or that

http://www.donzi.net/forums/attachment.php?attachmentid=29315&d=1180793637

:eek!:Looking good! Black and white- same colors as mine. I like the risers. They make it look a lot beafier

[The Hedgehog]

Yes, the risers do look good. Thanks.

Some folks dog on the 4.3. I like the way the boat handles with it. For 200 lbs more you could have a small block. That 200 lbs is a good bit in that small boat. Take out some weight with the exhaust and it is even more. The boat is crisp and you can fling it around.

You can always add some boost if you want to get scared:shocking::shocking:

The sound is interesting. Overall, I like it. Not everyone has one.