Mercruiser 5.7 questions.

[floating_viking]

Hi all, just joined this forum. A lot of interesting reading here. To my first question: I recently got a boat with a 1988 5.7 Mercruiser. I have no idea of the history of the engine(rebuilds, maintenance etc.). I took a day trip the past weekend with it, seems to run fine. What would be the best way for me to minimize risk of getting stuck with a dead engine out on the water? Get a boat mechanic to give it a good overhaul? I've played around with some motorcycle engines, but never boat engines. I have no problems replacing plugs, oil, filters etc. But I'm not sure if I'd start rebuilding it.

 

[thumpar]

I would start with the impeller. Check the bellows over and see how the gimbal bearing is doing. Get yourself an alignment tool if you plan on doing your own maintenance. I wouldn't overhaul the engine unless there is a problem.

 

[Bt Doctur]

Kinda doubtful the engine is original so...........................
Do a full tune up, including the filters. spare belts, spare tune up parts, Atleast pull the manifolds and risers for an inspection, risers live about 5 years so replacement should be considered to prevent overheating and water intrusion.manifolds about 10-12 years before replacement.
Have the drive fully serviced if you don't know or cant do it yourself.Alpha drives need impellers every 2 years no matter what .

 

[Scott Danforth]

Does the boat have an hour meter on it? if so, how many hours?
is the boat a freshwater boat or salt water boat. Most freshwater boats will last 40+ years on original motor, manifolds, and risers. Most salt water boats need manifolds ever 5 years or so.

Here is what I would do (and have done with my '88 vintage motor)

• pull the starter and alternator, take them to your local alternator shop, have them gone thru.
• clean all battery cable connections.
• check the health of your battery(s) (load test)
• perform a compression check - all numbers should be within 5% of each other, and over 150psi
• perform a pressure check of the cooling system.
• replace the raw water impeller
• keep up with the maintenance
• get towing insurance (either Boat US or SeaTow) because sometimes crap just happens.

 

[floating_viking]

Thanks for the tips. Gotta love these forums, best place for DIY guys. I've found out a lot of stuff on my motorcycle forum. On the other hand I have also spent a ton on upgrades on my bike from ideas I got on the forum.
I actually managed to find out that the impeller was replaced last year. Done by the mechanic at a neighboring marina, I spoke to the mechanic myself. I figure he's got no reason to lie about it. He remembered the boat because the previous owner had a smoking hot wife(trophy wife?). I met her and that's definitely true.

Gotta find out the serial number so that I can start getting the correct parts(plugs, belts etc).

The hour meter is unfortunately dead, so no use of that. I'll have to fix that somehow. The temperature gauge is also dead. Another thing to fix. The boat is in Ontario so fresh water it is. I did check the batteries, they are in great shape. The boat needs some TLC so that makes me think the engine might need it too.

I have a compression gauge so that won't be a problem.

To be continued....