96-97 454 Mag MPI - How good is it?
 

I am running a stock 96 454 Mag MPI w/ Mirage 23p prop. with approx. 550 hours. I maintain it constantly, oil, filters, impeller ect. I just replaced the plugs, distributor and rotor last season.

How durable are these motors? How many hours do you think one could get out of it? Are there any things I should look out for as the hours build? I use the boat 4 times a week.

When I run her hard (above 4500 rpm) the temp will climb from 160 to 165? I also notice the oil pressure fluctuate under hard runs?

Any info would be greatly appreciated.

If you have not already, Change out the exhaust manafolds.. If they go bad they will toast the engine.. Other than that just routine maintaince like oil , filters and water pump. If you have 550 hrs and are not burnig lots of oil then its fine. If it aint broke dont fix it except exhaust manifolds.Oil and temp sound fine to me.. You might get 700 -1000 or more hrs out of it. Just dont run wide open all the time.

Thanks.

I'm not burning any oil. Can you recommend some manifolds? Should I go stock? How do you know when they're bad?

It is much more a question of how you run it. If under 3000rpm most of the time on a lighter boat it will last 1000-2000 hours no problem. I got over 3000 hours out of a small block running below 2500rpm 95% of it's life in a light boat in fresh water. If you run 4000+rpm most time in a heavy salty boat cut that significantly. It's all in the manner.

You dont want them to go bad.. Or its too late.. I run in salt and most people I know say to change the stock ones out by year 4 or 400 hrs.. You will get lots of opinions on that on less and more years and hours. You can have them removed and inspected but its hard to tell even with them off the motor how much longer they will last.

These are on the cheap
http://www.cpperformance.com/SearchR...er=44&Vendor=2


And these are much better. And they have some resale value where the others do not.
http://www.cpperformance.com/detail.aspx?ID=9056

Chris

Thanks for this very useful info! I am going to look into this right away.

I don't run the boat that hard. Mostly keep it in the high 2's to mid 3's. With the occasional WOT. She cruises real nice @ 3400rpm.

As your engine is getting a little older, I would buy all of the input sensors; TP, MAP, ECT, IAT and maybe a knock sensor. Buy a cheap Rinda Code checker (about $40.00) I would also buy an IAC valve as it is one of the more common MPI maladies. All of these will cross to Delco or GM parts at a cheaper cost (except for maybe the IAC) Another nice touch would be a spare fuel pump, but I would pull the existing pump and cool fuel off of its block mtg and find a way to support it with cushion clamps, zip ties, etc.......It can be a bear to replace on some boats. Keep this stuff in a small tupperware container and you have alot of incidental breakdowns covered. Good insurance for a couple hundred bucks. Take Care, Dave

Thanks Dave!

I've already done the MAP, ECT, TP & IAC when I had a surge problem at low speeds. So I threw parts at it. Turned out the ECT was bad. The pump is not mounted on the block. They mounted it on a mount that has some give.

I will look into the code checker. The only one I found in the past was big $$.

Yup, my '97 454MAG MPI self detructed at around 550 hours due to an exhaust failure. It was running strong up until that point.