Mercruiser 4.3 Looking for better performance or Re-Power?

[Indywoods]

I have an 89 Chapparel 1900 SX, the boat is in super shape other that a cosmetic restore I'm going to do this winter. I've also wanted a little better performance, i.e. better ski pulling power. I don't need a lot more but I come from a ski tow boat world so this is underpowered. The motor has very few hours on it and is in perfect shape. I thought I'd repower with a V8 but I'm thinking I could just get better performance out of what I already own? Where should I look? Fuel Injection? Intake/Exhaust?

Or is it just better to repower? Cost is a factor but if I wonder if I can find someone interested in my motor?

 

[Scott Danforth]

My suggestion is a vortec intake, heads, and a 4-barrel carb.

 

[spoilsofwar]

Looks like your boat was available with a V8 option, and utilizes a doghouse style engine cover, so the space should be there if you wanted to go the V8 repower route. If you do, most will suggest you skip the 5.0 and go for a 5.7.

I'm not sure if the motor mounts will be different between a 4.3 and the 5.0/5.7, someone more knowledgeable will be able to fill you in on that. If they are different, your boat may already have provisions for either since like I said a V8 was an option.

The other thing to consider is your drive gear ratio.

Scott's suggestion is probably the easiest option to get more out of your 4.3 if you decide to keep it.

 

[Indywoods]

Thanks for the responses. How would I source the Vortec parts?

I'm redoing the back engine cover into a bench so I'm not worried about space. If I do repower definitely a 5.7 I wouldn't think a 5.0 would be much more power than the V6. As stupid as this sounds I'm leaning toward a repower because not only because of the extra power but I love the sound of a V8 on the water.

I really only want a decently powered, fun, reliable boat. I don't need stupid fast or loud. The way the boat is now getting up on a slalom is difficult and I'm a very good skier. I wonder what kind of lower unit issues I'd have with a repower?

 

[jkust]

You took the words out of my mouth. You will need a different ratio lower unit presuming you have an Alpha 1 with a repower. So much of this really boils down to your budget. Vortec heads (came about in 1996), new intake and 4bbl carb are extremely plentiful if you were to keep your current engine. Crate engine, new lower unit and controls are not cheap.

 

[Rick Stephens]

Sticking Vortec heads, Edelbrock Performa intake and Edelbrock 1409 carburetor should net around 240 HP on a '89 pre/non-balance shaft 4.3L block.

 

[ziggy]

fwiw. a maybe cheap fix to yer no hole shot w/slalom skier in tow.
don't know what pitch prop yer using. but i'll guess a 21p.

drop down to a 19p if so. if ya got a 19p now. drop down to a 17p.

you may get the torque ya need to get up on one just with a prop pitch change.

if ya do that, do watch the rpms when not skiing. you'll likely be able to go over wot spec with the lower pitch prop w/o the load of a slalom skier behind you.

good to hear some one is actually water skiing. cool. nobody does that any more.... yep, i slalom ski too, never been on a wake board like everyone else i see at the lake now a days.

another idea. when i was a teenager at dads cabin. we had a nice soft sand bottom. got so i didn't do deep water starts. knee deep water, a little slack in the ski tow rope and go. one hop and yer on top of the water. that boat had a 72 165hp L6 (less engine than your v6) engine w/17p aluminum prop. worked great... i'm 56 now. don't know if i could do that now though.

 

[achris]

I'm with Ziggy, prop change. I had a 1994 carbed V6 in my 20' cabin cruiser. Drop a prop size and that thing got out of the hole like a Polaris missile. Along the same line, have a look at a vented prop, like a LASER II or a HighFive. The prop vents allow the engine to spool up to the torque curve in an instant. Just warn the ski, he'll be up quicker than if you changed to a V8.

Chris.......

 

[jkust]

Sticking Vortec heads, Edelbrock Performa intake and Edelbrock 1409 carburetor should net around 240 HP on a '89 pre/non-balance shaft 4.3L block.

Do you mean 240 at the flywheel? A post 1996 4.3 that has vortec heads and intake plus adding the 1409 is only around 210ish at the prop isn't it? There's some old threads on iboats of people doing the conversion. I haven't seen them in a while though.

 

[Scott Danforth]

Vortec heads are $50 at a u-pull-it salvage yard or about $250 new

Intakes are on eBay dirt cheap.

If you go V8 with thru leg exhaust, it will sound just like the V6. You will also need a different gear ratio

It all comes down to budget. The head/intake swap is an afternoon project and will add a good 30-40 hp to your existing motor

 

[Rick Stephens]

Do you mean 240 at the flywheel? A post 1996 4.3 that has vortec heads and intake plus adding the 1409 is only around 210ish at the prop isn't it? There's some old threads on iboats of people doing the conversion. I haven't seen them in a while though.

I was basing on this setup being rated 230 HP in the Merc manuals with a balance shaft. Balance shaft takes 15 HP to turn.

 

[Scott06]

Just did this exact swap on a sea ray 200 sport that Previous owner didn't winterize and killed the original 4.3. Would second some of the above suggestions

Cheapest is try a different prop- 4 blade if you want holeshot for slalom skiing. I had good luck with a Michigan vortex 4 blade 16" pitch. At about $120 on line its the cheapest option.

If you want more hp vortec heads, intake and 4 bbl edelbrock is a great option for about $1400 total, and you don't have to pull the engine...

You can swap in a 5.0 or 5.7 for more power, both front mounts will be about 4" farther forward than the V6, if your boat came with a V8 most likely the pads are long enough to accept the V8.

I bought a Michigan motorz 5.0 silver package (new base engine, intake, carb, TBV ignition-260 hp), swapped over wiring, starter, alternator, ps, bellhousing (need the flywheel cover), coupler easy swap and saved a bunch vs complete engine. Only hitch was the throttle bracket (used merc off a webber carb), and metric bolts that were on v6. I didn't do the 5.7 because I wanted to keep my V6 ratio drive that only had 38 hrs. Had to swap the original 19" Vengance 3 blade for a 21" 4 blade Vensura. WOT is at 4900, with the 4 blade I can pull an adult slalom skier up no issue with 5 adults in the boat and a full gas tank. Tops out about 46 mph so the 4 blade definitely gives up some top end. With the V6 ratio in the drive a 21" performs like what a 19" would do on a "normal" drive ratio.

Bottom line the flat torque curve on the V8 is perfect for what I do which is tube, ski, and drink beer while the kids swim, very happy with it. In your lighter boat (assuming 2800 lbs dry? ) it would pull like a bull and fly on the top end, but you're wallet would be lightened much more than option 1 or 2.

 

[JoughBlough]

A stainless 4 blade is my recommendation. I torched my stock 3 blade first time I took it in the river...
My boat is a 2005 185BR with a 4.3 merc, alpha 1. {TKS } Prop made a huge difference.

 

[Lou C]

My ‘88 pre Vortec non balance shaft with the 4bbl Quadrajet was rated at 205 hp so adding the Vortec heads to that should net about 230 hp. I changed my old style OMC one piece exhaust for a later style center exit exhaust with 4” diameter elbow outlets and that alone seems to have added something to the top end. I have a 1.60:1 Cobra drive and I’m running a 15.5x15 prop. About as low as I can go in terms of pitch. It does get up & go compared to before...

 

[achris]

4 year old thread. Guys, read the forum rules!