I was told today a mercruiser 525 with about 300 hours is gonna need extensive top end work soon due to that many hours on the motor. Is this true? I was told lifters will start to fail ect. What doesn't make sense is a 502 in a car can last over 100000 miles but this will only last 300 hrs. Motor has never been beat on easy take offs not run at wot for excessive periods. Thoughts????

You have to take in consideration. The rpms that boat motors run At for long periods of time. And let alone the amount of load there at unlike a car that can roll down the road, is a lot less load on a motor.

Emagine driving ur car how often do u run ur car motor at 5000 rpms and how long not very maybe a few seconds. I'm not an expert or nothing but that's just what I have learned.

I had a stick 330 454 in my boat with only 475 hrs on it and by that time All the rod bearings where spun and it was starting to nock a bit to

valve train shouldn't suffer unless it lives at super high revs all the time, but wear surfaces where load is carried such as bearings etc will cop it.

Yeah I guess that's all true. Well I know the boat won't see high rpms for a few years since my newborn will be on it. So dads gonna just cruise the boat around now.

Even though, it has said to be driven mildly and has 300 hrs on it. Being you are 200 hrs from 500 hrs, which is pretty much the TIRED point for the 525. You should still have someone check spring rates or just replace them and pull you lifters, inspect for wheel bearing wear. If you lose a spring or lifter, the repair cost are going to out weigh, the cost of preventive maintenance.

Just think of it this way. how long will your car (say with a 502) last if you drive it all the time in first gear, going 65- 70 MPH on the highway at 4000- 4500 RPM's. This is cruising. Now hit the paddle, red line it (or close) for a while, say an hour. and I wonder if you make it home. Pretty much a typical boat ride.

Add to that, going up hill.....while towing 10,000 lbs

Would you be the first to go over 300 hrs and live to 500 without a problem, no, but if you have a failure it will be catastrophic and you will most likely lose your summer unless you have a long block standing by.

The lift and duration on the 525 is pretty hard on everything compared to a "Car". Those pesky leak prone CMI's should be checked as well.

Have the top ends done. Change the starters, impeller housings, and go boating for another 300 hrs with peace of mind

What's a typical top end job cost on a 525?