[paulcj77]

Have just purchased a '97 - 18' Shabah for a cheap price as the mercruiser 4.3 has seen better days.Because the condition of the boat is like new I've decided to have a brand new 4.3 mercruiser fitted,so can anyone advise me on 4 bbl carb or go mpi .Allso what sort of preformance I'll get and advice on prop size.
Thanks.
Paul.

[mikeyt]

Welcome aboard Paul. I have a '96 with the 4bbl carb 4.3LX and while it starts okay it would be much nicer to have the mpi version. The other issue you may run into is that the carbed versions run with a 1.81 gear ratio while the mpi uses a 1.62 gear ratio so you may have to consider changing out the gears with the newer motor.

As for the prop, most members here run either a 19" pitch 3 blade or a 20" pitch 4 blade to keep the WOT rpms within the recommended 4400-4800 range. Performance wise you should hit the high 40's with a fresh engine & prop.

When you have a moment, check out our Member Map and take the time to 'pin' your location?

[ColoradoDiablo]

Welcome to MOC Paul. Nice find on your Shabah.
I too thought about a MPI setup not to long ago. I decided against it about the time I saw the 7500.00 price tag for complete motor package! And like mikey said your going to have to do a gear change in order to reap the full benefits. So add another 1000.00 to that.
You might be able to go with the TKS motor for easier starts. I don't have any experience with them at all , but some of the members do I'm sure!

Once again , Welcome!!

Larry

[paulcj77]

Thank for the info guys,going to go for the mpi my mechanic seems to think I have the right gear ratio.
Unfortunateatly it's not marked on my upper unit so will need to work it out another way,our summer (not that we got much of one this year) is all most over so if that gears need changing too I've got till next year to save again.
to get it sorted.
Thanks again
Paul

[mikeyt]

Have a look at this link for locating either of the markings for the outdrive gear ratio.

[paulcj77]

Just an up date on the above,Now the new 4.3 mpi fitted and ran in for 11hours and loving it.
Although I could do with some more advice about the gear ratio,I'm running on the 1 .81 as with your advice
I confirmed,With a 21 pitch prop I'm getting 47 mph at wot 5100 rpm ( bit high I know only done this
once and briefly) if I change the gearing to 1.61 how will this affect performance and what
Other benefits will this effect .
Thanks again for your help
Paul.