How long before I need to consider engine overhaul or replacement?

[Old/newboater]

I spent a lot of time on the lake when I was young but have been out of boating for quite a while. Now that my kids are older (and I have a little money to spend) I am looking at used boats. I have a 2001 Mobius in my sights but it has 980 hours on it and I am wondering if I will need an overhaul or replacement anytime soon. (Assuming it has been maintained and not abused). It has been in freshwater only. Thanks in advance

[CRAZy440]

Well since your boat has a GM engine, I would scrap it now and put in a Ford engine. Just kidding. I'm just a grumpy Ford guy. Hey, I waited 16 years for them to make a new boat engine!$%#$@%#$

Joking aside, There are a lot of factors that have to go into deciding to overhaul a boat engine. Work load, maintenance schedule, oil usage, smokes on startup, rust issues in block or heads, etc... Good rule of thumb is 1500 hours max but start looking for issues of excessive wear at 1000 hours.

BTW car engines can go 3000 hours before watching close for issues. Car engines have extremely less work loads. Boats and cars just cant be compared.

[mmandley]

Other then all the above issues to watch the only true way to tell an engines health is a compression test.

All the cylinders need to be with in x% of each other and at least x PSI I don't want to post numbers as I'm not sure off them exactly.

[CRAZy440]

Other then all the above issues to watch the only true way to tell an engines health is a compression test.

All the cylinders need to be with in x% of each other and at least x PSI I don't want to post numbers as I'm not sure off them exactly.

Yeah this^^^^ Do that before you buy any boat!

[gregski]

My last boat had nearly 1500 hours on it and never gave me any trouble. I used to think that 1000 hours was "high" but now I think you could reasonably expect 1500-2000 hours without major service.

FWIW, our truck has nearly 6000 hours on it and I'm only now starting to think about age-related issues.

[kaneboats]

The ski schools would run their inboards to 2000+ hrs. Not sure about the current wakeboard schools.

[Old/newboater]

Okay first disclaimer:not a mechanic. That said I see numbers posted at around 175 psi but I thought most of these engines had ratios of approx. 10:1. With std pressure at about 14.5 wouldn't that equate to about 145 psi?

[mmandley]

Okay first disclaimer:not a mechanic. That said I see numbers posted at around 175 psi but I thought most of these engines had ratios of approx. 10:1. With std pressure at about 14.5 wouldn't that equate to about 145 psi?

10.1 refers to the compression ratio in the cylinder with relation to your cylinder heads. The higher the Compression the higher Octane fuel you need to keep it from per-detonation or pinging.

The 14.5 your referring to is the optimum fuel to air ratio which is 14.7-1 and this is whats needed so the engine doesn't run lean or rich.

This is one of the reason why gas engines have so many sensors on them to help keep this ratio exact all the time.

Diesels don't care, you run it rich it makes more power and dumps the rest as black smoke through the exhaust, Run it lean and it loses power, clear exhaust lol.

160+ is an idea compression per clinder, mind you this is a number I am pulling from memory and not exact. 175 is a really nice healthy engine.

A compression test is essentially testing the Valves sealing in the heads, and rings sealing on the cylinder walls, both are the main wear points in an engine.
If you see smoke <blue in color> at start up your Valve seals are going bad, this is allowing Oil to leak by into the cylinder and at startup you see blue smoke, White smoke is water in the engine and means a head gasket has failed.

I can go on and on, trust me LOL. Thats the basics of what is important in telling if an engine is tired or not.

Good thing is the Chevy Small Block 350 is called Bullet Proof for a reason, because they last and last. Idmar only stopped using them recently and switched to Ford because Chevy after more then 50 years is finally stopping production on them. The LSX series is the new engine Chevy is pushing. I personally would have rather seen the LSX engine adopted, so much easier to make gobs and gobs of power from those lol.

[Old/newboater]

Ok thanks for that. Next question. I also found an 02 mobius that has only 600 hours on it and a bit better equipped. Is it worth an extra 5 grand for the lower time boat? I know it's a little subjective but I appreciate different perspectives when weighing these types of decisions. Thanks to all for your input.

[zabooda]

Check NADA for a guide.