v6 Inboard on a 23' GM 4.3 200-235 hp?

[Hooligan]

Interested to know if anyone has any experience with the gm 4.3 vortec inboard/outboard and whether or not it would be an acceptable fit in a 23' CC.

I am considering the original mercruiser 888 from the factory and comparing the 188 hp to the 235 hp numbers of the vortec v6 and considering some weight savings... torque figures may be off from one to the other but no published specs for either.

Do you think performance would suffer with a 4.3 v6?

All thoughts appreciated.

[gofastsandman]

For a Hooligan , you sure don`t get out much. ?# of posts?

I think you know the answer. It may be fine in a 20 class.

[Bushwacker]

What's important in a boat engine is not peak hp that you'll seldom use, it's how much it puts out at the cruise/max continuous rating (at about 5"Hg manifold vacuum) and how much mid-range torque it puts out for climbing on plane. There is typically no substitute for cubic inches for that purpose. I'd pick a 350 ci V-8 over that 4.3L V-6 in a heartbeat. The 4.3L might be ok in a 20, but not a 23, which is a MUCH bigger and heavier boat. A V-8 will also be a much smoother running engine than that 90 degree V-6 which is not a naturally balanced engine like an I-6 or V-8.

A good friend of mine owned a Moesly 21 for 27 years and was on his 4th engine when he sold it. (The SeaCraft 21 is similar in beam and deadrise but lighter than the 23, with better ride and performance.) He was a gung-ho diver and ran it year round every weekend drift diving off Palm Beach carrying 4 divers + gear, and 8 tanks. It came new with a 150 hp I-6 Mercruiser with marginal performance; cruise with that heavy load was about 18 mph @ 5" vacuum. He burned out exhaust valves and cylinder heads often until he learned the importance of observing the 5" vacuum limit. He replaced it with a 165 hp I-6 Mercruiser which picked up cruise speed 1-2 mph. The next engine was a 260 hp Mercruiser V-8 that would easily cruise at 22-23 mph at about 9" vacuum, with much better life on the exhaust valves and seats. His last engine was another 350 chevy, but a Volvo I/O version rated at 290 hp and it was his favorite of the bunch, with a WOT speed of about 50 mph!

[gofastsandman]

Originally Posted by Bushwacker

What's important in a boat engine is not peak hp that you'll seldom use, it's how much it puts out at the cruise/max continuous rating (at about 5"Hg manifold vacuum) and how much mid-range torque it puts out for climbing on plane. There is typically no substitute for cubic inches for that purpose. I'd pick a 350 ci V-8 over that 4.3L V-6 in a heartbeat. The 4.3L might be ok in a 20, but not a 23, which is a MUCH bigger and heavier boat. A V-8 will also be a much smoother running engine than that 90 degree V-6 which is not a naturally balanced engine like an I-6 or V-8.

A good friend of mine owned a Moesly 21 for 27 years and was on his 4th engine when he sold it. (The SeaCraft 21 is similar in beam and deadrise but lighter than the 23, with better ride and performance.) He was a gung-ho diver and ran it year round every weekend drift diving off Palm Beach carrying 4 divers + gear, and 8 tanks. It came new with a 150 hp I-6 Mercruiser with marginal performance; cruise with that heavy load was about 18 mph @ 5" vacuum. He burned out exhaust valves and cylinder heads often until he learned the importance of observing the 5" vacuum limit. He replaced it with a 165 hp I-6 Mercruiser which picked up cruise speed 1-2 mph. The next engine was a 260 hp Mercruiser V-8 that would easily cruise at 22-23 mph at about 9" vacuum, with much better life on the exhaust valves and seats. His last engine was another 350 chevy, but a Volvo I/O version rated at 290 hp and it was his favorite of the bunch, with a WOT speed of about 50 mph!

The wonderful mind makes many good points here. Spin and burn or loaf and be smart.

Your choice,
GFS

[cdavisdb]

When it gets rough, the lack of torque in the v6 will make you crazy, jumping on and off plane trying to keep a reasonable speed.

[bigeasy1]

Bushwacker as always,gave great advice.
You won't be happy with the 4.3.I have a 23 Tsunami with a 350 5.7 GM/Mercruiser and Alpha drive,and even with that it's not a rocket ship at top speed.
It does however,hop up on plane almost instantly.and runs effortlessly at cruise speed.I've had a few similar size boats with the smaller,305 GM engines,and they were much slower out of the hole,and were harder to keep speed in nasty water conditions.

I'm probably around 260-270hp on my 350 and am spinning a 15-1/2x17 Mirage SS prop.This combo seems to work the best for me.The 350 definitely has the torque needed to move this boat in all situations,and doesn't have to work as hard as lesser cubic inch engines.
Somewhere,I have my performance numbers written down,but I'm around 36-38 mph at wot,and in the neighborhood of around 25-27 mph at 3000-3200 rpms.
Actually,I'd like even more HP,but at the time I did the restore,I was able to get a bargain on the 350.
Had money not been an issue I would have gone with a 383 stroker,or maybe even a 454.I may be mistaken but I think Water Rat,Chris Downey runs a 454 in his 23.
I'd like to see what his performance numbers are.

[ct9amr]

Coming from Shamrocks I would not recommend the 4.3 as an inboard in 23ft.
You definitely need the TQ of a V8 like it has already been stated.

If your doing the V6 for economy its probably not going to work well either since you will be pushing the engine hard.

[Wags23]

When I bought my 23 cc it had a 4 cyl ( half of the 460 ford) AND IT WAS A DOG!! It had no ttop and the hull was in good shape.Probably because it wasnt run hard (you couldnt). I was out about 30 miles and it started getting rough 4-6 footers and it was struggling to get over some of the bigger ones. In went a 350 merc. You will never regret it go with the 350 it was a whole different boat. POwering up waves,cruise, getting on plane, everything. I just switched over to diesel v6 tdi and need to get it propped right but seems to have plenty of power.

[Hooligan]

Excellent advice guys, I thank you for all your input. The reason I was tempted was a near new 2010 4.3 235 hp for sale for short money... sort of thought I could save some weight and also put a larger hp motor in than the stock from factory and be in good shape.

Not worth the risk i guess, huh.

So the lesson taught is that should settle for a slightly older 305 or 350, preferably the 350 from what I have read above. Naturally the 350 seems a better choice than the 305 because of the near identical weights yet differing horsepowers?

Great to see you guys are willing to share from both your successes and mistakes. Thumbs up. As usual, this site is a great group and I'm glad you let me be a part.

Thanks,

Hooligan

[pelican]

Originally Posted by Hooligan

Interested to know if anyone has any experience with the gm 4.3 vortec inboard/outboard and whether or not it would be an acceptable fit in a 23' CC.

I am considering the original mercruiser 888 from the factory and comparing the 188 hp to the 235 hp numbers of the vortec v6 and considering some weight savings... torque figures may be off from one to the other but no published specs for either.

Do you think performance would suffer with a 4.3 v6?

All thoughts appreciated.

besides the performance,allready dicussed,if your plan was to reuse the existing drive yu were going to make a huge mistake - very costly mistake as well.the older alpha drives,these have high pressure low volume water pumps - the newer alpha gen II drives have a high volume,low pressure water pump - with all that,the older drives are not compatable with the newer vortec engines...

the smart play for you,is to pick up a package -read that as engine/drive and transom assembly - if you're really smart,you're gonna go for the harness,smart craft set up including guages.doing this,you're buying new,not used/rebuilt ,and the best part,you're not attempting to "adapt"...get the merc 5.7 MPI/bravo drive - this is what's pushing my 23,it's a bulletproof,incredibly fuel efficient package - it's an '03 set up,have had ZERO problems !