I bought this boat last year. 1993 454 magnum (carbed 365hp) bravo one in a formula. Drained the block and winterized it last fall, but didn't change any fluids.

I'm planning to change the oil before we put it in the water, and considering the switch to synthetic. The boat has lowish hours (around 375), but it is a 1993, so it isn't like it is a "newer" engine. Would any recommend against the switch?

Also, is it standard procedure to change the fluid in the outdirve every year?

I've heard some say they put in a new pump impeller in every year as well... necessary?

Thanks,
Scott

All those things are the cheap things you can do to prevent expensive bad things from happening. So yes, I do mine every year. I live in a pretty clean lake so I have skipped impeller before for a year but it's still not a great idea.

I haven't done it but I've certainly heard of people changing to synthetic and causing leaks. I might be inclined just to keep running whatever they have been using.

I change engine and outdrive oil as well as seawater/fuel pump oil every 20 hours. Change oil/outdrive oil prior to winterization to get rid contaminants/water in oil. Impellers every other year.

Change Drive lube once a season or 50 hrs.
Switching to synthetic oil will be fine and there are no negatives. I prefer Mobil 1 15w-50. Walmart for about $26 for a 5 qt jug.

Being that those are flat tappet cammed engines, I'd run an oil that has a good amount of zinc in it. Diesel oils used to, but I read they have pulled some of the zinc out as of recent.

^^^Bingo^^^

I'm not a mechanic - but this is my two cents

1. I would keep the same oil that has been in the engine since day 1-- Synthetics in my opinion are the best out there - Especially Mobil 1. But if you are doing well with the current oil there is no need to change nor will it offer any significant benefit. I've heard the rumors of leaks with switching to synthetics - personally I think that is a bunch of bunk - but again I'm not a mechanic.

2. I change drive oil every year - engine alignment check every other year.

3. The impeller is dependent where you boat. In my experience I changed the impeller after 2 years and with about 150 hours run time - it looked as good as new. My intention is to change in in about 4 years. -- but again that is where I boat - very little if any silt or sand.

All the best

3pointstar

Synthetic, synthetic, synthetic... Mobil 1 15w50. Zinc is not an issue with Mobil 1. Even calls out "for use with flat tappet cams".
https://mobiloil.com/~/media/amer/us...pecs-guide.pdf

Yep M1 15w50 is hard to beat. Currently $22 for 5qt jugs at Walmart with a $12 mail in rebate till 5/31.

My two cents.
I change engine every 25 drive every 50. But when I stored over the winter I would change at the end of every season so it sits with nice clean oil in both.

As for the impeller, I would do them every spring because my thought is the rubber has been in one position the whole winter. It's not like they are expensive.