aquaforce

I see the 97 502MPI has V-belts and the arrangement of accessories appear different on the engine so what else is different between a 97 and a 98 502MPI?
Is there build up pros and cons that are different between these two?
I didn't realize there was any difference between the years and now that I see the differences it really has me wondering about powering up a 97 compared to a 98.
Tell me what you know.
TIA

buck183

I don't know the answers to your questions. Sorry.

Something did stand out in your post to me though. I owned a 1996 boat with the same year model 502 MPI in it. This motor had a serpentine belt system on it. The other boats of the same year model with the same power plant that I saw also had serpentine belts on them.

What makes you say the 1997s have V belt systems?

Buck

aquaforce

A 97 Formula boat with these were V belt and a 98 Formula had the serpentine belt. When I noticed this I looked the engines up by suppliers and found the same thing. That got me wondering how much more is different?

buck183

That is odd. I guess add to the confusion by saying the 1996s have serpentine belts.

Buck

Young Performance

1998 was a crazy year for the 454/502 mags. There were/are several differences. You can not base anything off of just the year with those engines. In 1998 alone, you could have either a Mefi 1 or a Mefi 3. You could also have a serpentine belt system or you could have a v belt accessory system. Mercury was supposed to have changed from a V belt to serpentine at the same time that the ECM was changed from a Mefi 1 to a 3. They was not supposed to have a V belt engine with a Mefi 3, nor were they supposed to have a serpentine engine with a Mefi 1. Both were rare engines, but they are out there. When dealing with any of these engines, you HAVE to go off of serial #. All pre 98 454/502 Mag engines had V belts and a Mefi 1. All 454/502 Mag engines after 98 were serpentine with Mefi 3's. 1998 itself was a completely jacked up year.
Eddie

articfriends

iTrader: (1)

Another thing that happens I have seen is smaller boat builders might buy a powerplant for a boat then it sat a yr before going, ie a 1998 boat with a 1997 or 1996 motor, might have been NOS that they found too when boat was assembled. I just rebuilt a HP500 efi for a guy's 1999 Fountain and the motor was a 2000, his hull might have been built and year assigned to VIN then it sat before being rigged , fwiw, Smitty

Hook'em

My '97 502 has V belts. Also I believe the VST system was on the V belt MEFI 1 motor and Cool Fuel was on the serp MEFI 3 motors.

BUP

iTrader: (9)

It goes by engine serial number runs per part changes and service info and OEM set up. It has never went by year models for looking up parts or proper service info or OEM set ups. When ever you take your boat in to a OEM marine dealer they look at your engine serial # for the parts and proper procedures. Post your the engine serial #'s and I can tell to a T what the difference is.

And that is correct boat builders and dealers would buy X amount of engines then install those brand new engines a year latter or years down the road in brand new hulls.

Many years ago dealers would rig new boats with new engines packages to save money on new boat purchases thru the manu.. OMC dealers did this alot way back in the day. examples I have seen, dealers can persay install a brand new 1993. engine package into a 1996 brand new boat hull. Not an uncommon practice back in the day. Heck I seen brand new 1993 Yamaha sterndrive engine packages installed in 1999 brand new hulls back then to. Just saying

Gimme Fuel

I will throw a wrench into that statement. My original 97 502 had v-belts, MEFI1, and cool fuel. Service manuals I have broke it down to 1997 and 1997.5 model years. 1997.5 being cool fuel.

aquaforce

Thanks for the info everyone. This is hitting around all the things I was wondering about.
So more questions resulting now. Is the MEFI 3 computer one that can be programmed and the MEFI 1 can not be programmed? Do I understand that right?
Can the MEFI 1 computer be used for any power-ups more than stock?

My thoughts were to bump them up to 500HP NA. Later I could whipple charge for more HP or another thought I had was to stroke them to 540 cid but if this MPFI-1 can't do that then there is more cost for the fuel system mods. Can the MPFI-3 be used on the earlier engines?

I don't have the boat where I can get engine numbers or I would post them. I have the mfgr build sheet for the boat but the ENG/O.D. numbers are not listed. The mfgr build date for the boat is May. The engines are V-belt in a 97 model boat and that is all the data I have till after 7/6/15.


Oh yea, is there any other internal differences?