Swapping a Merc 165 4cyl for a 4.3 v6 PLEASE HELP

[FLSeville]

Hello, Newbie Here


I have an 87 Sea Ray Seville with the factory Mercruiser 165 4 cylinder. The motor is completely worn out and I would like to replace it with a 4.3 V6. I'm new to the world of marine mechanics and would like to know what I might get myself into. Would it be a fairly simple engine swap, or will I have to do major work?

Thanks Everyone...

[Jango]

Unless you have access to an inexpensive V6, It would be Far easier and less expensive to rebuild the 4 cyl. or buy a rebuilt engine or short block (no head or accessories).
If an increase in power is desired, you could equip it with a Ford 429CJ Cylinder Head for power at or near the V6.

[marshmat]

How was the boat's performance with the 4, and how much longer do you want it to last?

If you want more acceleration or more speed, swapping in a 4.3 EFI is probably the way to go. You can get late-model or rebuilt 4.3 motors for a few thousand bucks. If the boat performed fine with the old motor, you might consider a new 3.0 litre four-cylinder. Either of these two options will run you a few grand but will last another 20 years.

If your current motor is really wrecked (which, for a 20-year-old 3-litre, would not be surprising), it's probably not worth rebuilding. You can swap heads and cams all you like, but the 3.0 really doesn't have much performance potential. To get 200hp out of your current 3.0 would cost far more than getting 200hp out of a new, stock, 4.3 (which comes with a warranty, unlike a customized 3.0). If you only intend to run the boat for a few more years, though, and don't mind its current performance, rebuilding your current motor could be worthwhile. Rebuilding it to its stock condition will certainly be cheaper than putting in a 4.3.

The repowering is complex and tedious, but not impossible for you to do. It's easiest to just pay a yard to do it. If you want to do it yourself, have a yard pull the old motor and mount the new one, then do the hoses and electrics yourself. Actually moving the block requires an engine hoist and a crane operator's licence. The rest is well within the ability of a gearhead with a good shop manual.

[Jango]

Matt, The 165 mercruiser is a 3.7 not a 3.0. It's half of a Ford 429/460 big block and can easily be increased to 200+ H.P. Stock 165/175 bottom end torque is actually higher than the 4.3,s

[marshmat]

Oops- sorry Jango, my bad. I think I read 185 instead of 165; the 185 c.i. is the 3.0L while the 165 (3.7L) would indeed be the half-Ford. And that one could indeed be worth tweaking if it's not totally fried. Why can't the builders just standardize their nomenclature...

[Jango]

Matt, I totally agree on what you said about standardization. I guess they stopped building the (165hp), 4 cyl. before everything went metric. I still think in terms of cu.in.