Engine/Outdrive interchangability.....

[2kwik4u]

I've been curious for awhile as to how different engines interchange with different outdrives.

Good friend of mine has a 22' Celebrity cuddy cabin. Nice boat. It came with the 4.3 V6 in it, and he wasn't terribly happy with the performance. So, he took it to a local marina, where they charged him an arm and a leg to swap over to a 350. Excellent choice IMO, as the boat now runs ~60mph after all the work, where before it was a good day to break into the 40's. Huge performance increase, but also a huge price tag.

This kinda has me thinking about my little 18' boat. It currently has the 3.0L 4cyl, and I'm curious what it would take to change it to a 4.3. I'm obviously not going to be doing it anytime soon since the boat runs, and drives great with the 3.0L, however I can see getting a larger boat in the future, and if this one is paid off, it might be a fun project. I've also been around the S-series scene for quite a few years, and know a good deal on how to build a stout 4.3 in the 260-270hp range (these are wheel HP numbers as measured on a dyno in a truck so I have no idea how that translates to water hp numbers). Am I looking at a complete new lower unit to go with the new motor? Will the unit thats on there now hold up to more powerfull motor? I'm 100% sure there is a re-prop involved. Should I be concerned that the weight of the 4.3 is higher, and will make the boat more aft-heavy? I know that greatly effects my buddy's celebrity.

Just some thoughts, figure this was the best place to "bench race" with ideas like this.

[TiniTime]

when changing the motor, there are a lot of considerations.  If you plan on using the same outdrive, you may have to change the gear ratio and the prop will also need changing.  Make sure the stringers are arranged in such a way that they can take the motor mounts and support  a larger, heavier motor.

[cyber]

And note - boat 4.3 is way different than a car 4.3...

Has to be able to turn enormous RPM's continuously, etc etc etc...

Boat motors are more like Nascar motors in that sense...

[2kwik4u]

And note - boat 4.3 is way different than a car 4.3...

Has to be able to turn enormous RPM's continuously, etc etc etc...

Boat motors are more like Nascar motors in that sense...

Yea, the overall difference isn't that great. A good BALANCED rotating assembly, good bearings, as well as a non-balance shaft block is what makes the difference. The heads/cams/pistons/rods are all very similar. As well as using the marine accessories.

I'm obviously new to the boating world, however I can't see the differences on internal assembly being that great.....Even if they are, it's not like I can't put the right components in it when it's being built.

Keep in mind, I'm still bench racing, and not making actual plans.

[gmricketts]

The cam timing for the exhaust valves is diffrent also to keep water from the wet exhaust from entering the cylinders and hydrolocking them. Bad stuff!!

Plus there is all the diffrent marine parts to kep the boat from going BOOM!!

George

[2kwik4u]

The cam timing for the exhaust valves is diffrent also to keep water from the wet exhaust from entering the cylinders and hydrolocking them. Bad stuff!!

Plus there is all the diffrent marine parts to kep the boat from going BOOM!!

George

Hadn't thought about the wet exhaust. I suppose a set of stainless headers would get too hot?

I had thought of moving to fuel injection, as well as coil on plug ignition. SO I'm not sure if spark arrestors are still needed with those improvements. In fact I have no idea where the current spark arrestors are. I have to think they are on the carb, and maybe on the distributor cap? Where else?