1998 Mercruiser 4.3LH Vortec performance upgrades

[Stillreelin]

About 4 years ago I replaced the original 1998 4.3LH 4 barrel 225hp V6 vortec with a remanufactured one. It never had the punch like the original engine did. So I still have the original engine and was going to take my time and rebuild at my own pace. With that being said the plan is to have block and heads cleaned and checked. Keeping the bottom end pretty much stock except boring .030 and replacing piston and rings. Now most work will be on the top end. I am not looking for crazy rough idle 350hp engine. I would just like to add around 30 to 40hp. So I was wondering if someone had done already or could suggest a nice camshaft, lifter combo etc? In the research I did on the internet most builds were on a 180hp engine and they got it up to 222hp.

 

[Scott Danforth]

I would use proper pistons and not the stock 4-relief units. there are stroker cranks, however they are about $3k each, so not worth it unless your restricted to a class of racing

proper pistons, a decent camshaft, some port work on the heads, proper intake and carb and 250hp at the prop is achievable. anything more than that and it would be much cheaper to simply go V8

 

[alldodge]

The original 4.3L 4BBL was rated at 205HP. My guess if you picked up a non-vortec V6 then it would have had 175HP, and if it cam out of or built for a car then it would be 180HP but not have the right cam.

All that said, if you take your original motor, bore it .030 over, zero deck the block, or plus up the pistons to zero deck, and then use a .043 head gasket, your standard cam will be fine, and your HP will be increased.

 

[bman440440]

one thing to keep in mind with the vortec heads... DO NOT do port work on them... google is your friend on this.. look it up... if they are non vortec heads then yes port work... the main reason for this is that porting a vortec head will only help you out with a big cam and higher rpm's... that would be a no no to run on a boat because of the likely chance of water getting sucked back into the engine... IMO just do a basic rebuild ditching the relief pistons and getting a LITTLE bit hotter cam from crane (call them up and tell them what you are doing and they can spec a good marine cam for you) and your good... you might be looking at about 240 HP... that's my 2c you can take it for what its worth

 

[Stillreelin]

Summit sells a marine 262 V6 rated at 262 HP for 3,129.00. If I was in a hurry I would snatch it up. I am using some of the ideas off that build. So for the pistons I was going to go with Keith Black hypereutectic pistons. I was not going to port and polish heads. Just clean and replace with new speedpro valves and stronger comp cam springs. I will get in touch with comp cams and see what they suggest. Thanks Guys!