Mercruiser 470 Fuel Pump Replacement - Success

[Dressmeister]

I bought a sweet 1980 Family Fisherman 22-2 last year. I'm working through the critical safety and reliability issues, then moving on to the nice-to-haves.

Fuel pumps for the 470 are not easy to find, so I had to gamble on a "universal" mechanical fuel pump from Amazon. It fit, and the installation went overall very well.

Very, very hard starts were the inspiration, but there were added benefits. Previously, at WOT, I could hit about 4,000 rpm at about 30 knots. With the new fuel pump, the starts are much, MUCH easier and at WOT it will run right up to 5,000. Of course, 4,000 is just enough to keep us on a plane, so that's our functional limit.

Documented on YouTube: https://youtu.be/VNJ8tfjxVhg

[GoneFission]

Electric fuel pumps are the way to go!  Did you put a regulator on, or is the pump 5 psi or less?  You don't want to overpressurize the carb and have the needle unseat.    

Also, the 470 is NOT a high-RPM engine!  I've replaced some broken pistons from folks who want to wind them up - keep it below 4000 if you want it to last.  The 470 uses an Mercury alloy block and a cast iron head from a Ford 460 V-8.  Don't overheat them and don't run them too hard and they are pretty durable.  Also, check the oil fairly often, as the seals sometimes fail and that allows coolant to mix with engine oil.  You will see this as a frothy mix (good for beer - bad for engine oil) on the dipstick.  The other weakness on these engines is the alternator.  But you can change it out for a later model from most later Mercruisers - that's a pretty easy fix.   

Good luck and see you on the water! 

[Dressmeister]

Thanks for all the tips, Cap'n John.

As you may have seen, I replaced it with another mechanical fuel pump. I thought about wiring in a low pressure electric pump, but I wasn't sure about all the interlocks with ignition, oil pressure, etc.

We were a little surprised at how much more power we got with the new pump. It ran up to 5k really fast, then we backed it right back down to 4k. We run around 4k when necessary.

The boat (22-2 FF) get's up to speed fairly quickly, but our top end is limited by engine speed, not power. In other words, we're leaving a lot of torque on the table.  Is there any danger in switching to a prop with a little higher (steeper, more?) pitch? I don't actually know the pitch of my current prop.

The previous owner installed a big new alternator, thankfully.

[GoneFission]

Look on the prop and see what you are running.  You can go up 2" in pitch and get the RPMs down a bit - figure 200 RPM for each inch of pitch - so adding 2" of pitch would drop somewhere around 400 RPM.  With the right prop, you should do about 4400-4500 RPM at wide open.  That would give you a pretty good cruise at 3500-4000.   Your boat is under-propped if you can make 5000 RPM - she will have a good hole shot, but will be slow and screaming at the top end.     Running a 470 for long at 5000 RPM will help introduce you to a new engine.