Engine Question
 

First time on any forum, ever. Anyway I picked up a 96 24' outlaw with a 502 magnum Mpi at a insurance auction, it was a flood recovery so I knew I'd have to rebuild the engine, what I didn't know was it had a cracked block. I bought two mercruser 420 cyclone engines ( got a good deal). Anyway the question is to any knowledgeable boat people is, can I use the fuel injection system off the 502, on the 420 and could I use the roller cam and lifters also?

THe ecm will need to be reprogrammed. You can do a roller cam/lifters, you just need to get the correct lifters for the block, correct valve springs etc....

Thanks phragle . The 420 is going to get freshened up, rings bearings etc. they have good heads which will be sent to the machine shop, factory gold crane roller rockers, but with flat tapets, is using the roller cam out of the 502 worth messing with?

Thanks phragle . The 420 is going to get freshened up, rings bearings etc. they have good heads which will be sent to the machine shop, factory gold crane roller rockers, but with flat tapets, is using the roller cam out of the 502 worth messing with?

Have you priced a decent set of retro roller lifters? (assuming the 420 is a mkIV block) If you are going to do a roller conversion, go with a cam that meets your needs. An off the shelf cam fitting your needs could easily be less expensive than the lifters.

Is the 420 a mkIV and the 502 a gen VI ?

How much power are you trying to make?

By saying "good heads" do you mean they arent wasted or are they good aftermarket heads ?

The 420 still has essentially the same rectangle iron factory GM heads as the 502. What year 420's? Iron GM heads that spent 20+ years in salt water are scrap metal. They rot through at the end exhaust guide. Your 502 heads, being much younger are gonna be waaay better condition. Same chambers, ports... Just need to have the valve studs threaded to 7/16ths. BUT, when a set of heads land in a shop, they generally cost 500 on up to get back. So consider upgrading the heads instead of reconditioning what you have. The 2 cams are very little different in profile and power output. The biggest diff between a 420 and a 365 hp 454 mag is the 420 is rated at the flywheel. The 365 rated at the prop. Whatcha got for exhausts? The 502 still used factory merc wet-joint center dumps. And they cracked too. Speaking of cracked 502 blocks, where are you? I am playing with fixing cracked 502 blocks. Philly area.

Non engine related however make sure and inspect all and any areas where water could have made its way in to the boat and remained saturated for any llength of time. Especially transom and stringers. Sometimes individuals have a tendency to drill, cut etc for something and don't seal off properly or at all. Hopefully all is sealed and no issues but just never know who did what before flood damage. Just a heads up anyway and good luck with your project and welcome to the oso.

Flood boat - if the electronics, ignition systems, wiring harness and ecm have been under water, I really never seen any of that fair very well especially down the road. I am dealing with flood boats as we speak thru various Insurance companies.

could just buy my 525 sc and swap your accessories on to it and be done...just had to mention that lol

Stewart

Word around the campfire is several of them are being purchased from insurance companies etc and hahauled up north to sell. I can't imagine being an adjuster down in parts of Florida and Texas right now.