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MadeInVirginia
02-26-2003, 04:51 AM
Ok....It's not exactly a hot boat, but I want a little more. I have a 1989 4.3L Mercruiser, with a 2 barrel. It puts out an anemic 150 HP at the prop. I would like to put a 4 barrel carb on it. Other than the intake manifold and carb, is there any else that needs to be done when I make this switch? Are there any other upgrades that will help this engine? I'm not trying to set the water on fire, just want to get a few more reliable HP out of this engine. Thanks!!

1BIGJIM
02-26-2003, 07:47 AM
Just my 2cents, but I don't think you will notice any difference. If you are lucky a couple hundreds of RPM and 1MPH. I started in your shoes years ago(started with an inline 6) and realized for boats, the more cubic inces the better. We always look for more. Currently I have the 454 big block and looking at upgrading to the 502. Never satisfied.

MadeInVirginia
02-26-2003, 09:13 AM
Thanks for the input BigJim. Right now, the budget dictates I stick with this boat....re: new house. I'm not so much interested in more speed, as more power. More than 4-5 people in the boat, and it's really sluggish getting out of the hole. A 4.3L (262 cu in) should have enough displacement to put out more than 150 HP without breathing hard. I may not get more speed with a 4 barrel, but hopefully it would help my heavy load hole shot. How was your fuel economy affected? Thanks!!

John Cobalt
02-26-2003, 10:23 AM
Made in Virginia,
I owned a 92 Mariah MX19 with a 205hp at crank 4.3LX liter Merc running a SS prop and so forth. It had the 4 barrel and the boat would run 52 MPH and was fairly snappy. I have been in a few Two Barrel boats and there isn't a whole lot of difference but maybe enough for you. I think you could get 25hp out of the swap but as was stated you may not see a big increase in speed or hole shot, it would depend mostly on how big the boat is and how efficient the hull. I would think you could clear 175hp. My suggestion before going to all this work would be to try a different prop. Go stainless steel if your running an Aluminum. and sometimes changing from one brand SS to another you can find an advantage. I had excellent results from the Michigan Wheel Prop called RAPTURE. If you are running 200 to 300rpm under the reccomended max RPM you may want to drop pitch by 2 inches... 21p to 19p you will see a huge difference in whole shot.
I've been there too! Let us know.

rivercrazy
02-26-2003, 10:51 AM
I've heard torque shift props work pretty good on that set up.

MadeInVirginia
02-26-2003, 11:27 AM
My boat is an 18 foot Ebbtide and I'm using a 21" pitch aluminum prop. Where I boat, there can be a lot of debris, so I'm hesitant to switch to stainless, due to the probable dings, and cost to repair stainless. With just me in the boat, and light fuel, it runs in the 5000-5100 rpm range, on a cool day. Otherwise, it's right around 4800 rpm. Right where it should be. Speed is about 47-48. If I won't see much difference, then it's probably not worth the effort. Especially since the set-up I have now starts, idles, and runs perfectly.

John Cobalt
02-26-2003, 01:20 PM
Virginia,
The stainless props will not flex as much as the aluminum so my personal opinion they give better all around performance. BUT as you indicated the conditions you boat in may not be conducive to using these so since you are in those conditions it is obviously a good idea to have a spare prop so do what I used to do. Have a 19P handy on the days when you and your friends want to ski and board and cruise and just watch the RPM's if your empty. You will see a pretty noticeable difference in your whole shot when your loaded down and should be impressed with the power of the 4.3 as is. As long as it is in good state of tune.

John Cobalt
02-26-2003, 01:23 PM
Extra aluminum prop should only be around 180 or so, so it is a pretty good compromise and it may save you from having a weekend cut short by trashing your 21p. Additionally if you have a spare 21p aluminum right now try out a 19p and see if you can work a trade for minimal money

John Cobalt
02-26-2003, 01:26 PM
I tried the Mercruiser version of the Shift Prop and didn't like it on my Mariah because the shift really hit hard like powershifting a 68 big block camaro,, I didn't feel that was good on the drive so I opted not to purchase it and went with the 21p Rapture Stainless for a lot less money.
I don't know how the Land and Sea Torque shift works it may be better than the Merc.

HP350SC
02-26-2003, 08:41 PM
I had an '88 4.3 2-barrel in a 17' Bowrider.Speedo said 46 mph. Then I installed a 390 cfm Holley and GM non-EGR intake which took it to 52 mph on speedo. You WILL lose hole shot going to a 4-barrel. As I recall,the 2-barrel had surprising out of the hole perf. I agree with the others,check tune-up and timing and drop your pitch when loaded up.

77charger
02-26-2003, 09:54 PM
I have an eliminator with a 350 mag 270 hp and i spin a 21 p stainless to 4800 at 57mph.I think a 21 might be to much for your boat for out of the hole.My dad also has a 19 ft reinell his boat has a fuel injected 302 in it he runs a 19p alm prop his boat runs at 4800 rpm speed i can guess around 50 but his seems good out of the hole i know it can pull me up on 1 ski with 4 people in the boat w/ no prob.

MadeInVirginia
02-27-2003, 05:09 AM
Thanks for all the input. It sounds like I should probably just stick where I am....for now. If it ain't broke, don't fix it, and for a 14 year old boat, it really runs well. Dropping down in pitch may be the best solution.

XTRM22
02-27-2003, 06:02 AM
I can totally relate to the budget issue, a few years back a friend of mine had a 17' closed deck vee I can't remember the brand but it had a land and see torque shift with the 205 hp V6. I would totally recomend trying that set up it worked great on his boat. coming outa the hole it would stay wound up at like 19" but when you started trimming up it would open 2-3". It shifted like like continuously, not like banging gears. The only draw back was setting iit up was a pain in the ass if you ever had to change it. Good Luck
Chuck