5.7 Alpha One Gen One Overheating

[4ceesuns]

I have an 87 Searay with the Alpha one. It has been used in salt water forever. I'm not sure the history on the motor but it is in very good condition, clean, runs great, gets winterized every year. The last several seasons I noticed the max RPM I can continuously run (without overheating) has been lowering each year. When I bought the boat five years ago I could cruise at 4400 RPM. Each year that dropped to the current cruising RPM this year of about 3500 RPM. Anything higher and runs hot, at 4500 it would overheat if run continuously. So I'm asking everyone what needs to be replaced to restore the cooling on this motor?
Thanks, Gene

 

[MarkSee]

Re: 5.7 Alpha One Gen One Overheating

I'm not sure the history on the motor but it is in very good condition, clean, runs great, gets winterized every year.

Does the "winterized" include changing the impeller? Do you know when the last time that was changed?

Welcome to IBOATS.

Mark

 

[Don S]

Re: 5.7 Alpha One Gen One Overheating

Winterized in itself means little. Some consider draining the block as being winterized and does nothing to help anything else on the engine and drive. Impellers should be changed every other year at least in salt water. Manifolds and elbow need to be checked to make sure they aren't plugging up. Thermostats go bad as well, along with basic corrosion.
So what all have you checked so far?

 

[4ceesuns]

Re: 5.7 Alpha One Gen One Overheating

Thanks for the fast reply. The winterizing has been just that.

The impeller has been changed every year for years and was just changed again at the beginning of this season.

The thermostat was changed last season and seems to open fine and the motor settles on the correct temp and only heats up a little until I go above 3500 RPM then really runs hot as described earlier.

This motor has been well maintained, oil changed every season, spark plugs every couple years, and the thermostat and impeller just a few weeks ago. So what do you think guys?

 

[Don S]

Re: 5.7 Alpha One Gen One Overheating

Manifolds and elbow need to be checked to make sure they aren't plugging up.

You didn't mention the manifold and elbows. Time to pull the elbows and check out the water passages.

 

[4ceesuns]

Re: 5.7 Alpha One Gen One Overheating

OK. I assume the elbows are on top of the manifolds. I also assume this can be done with the boat in the water. Should I be looking for a restriction that can be cleared out, or peering inside the manifolds to look for corrosion, inspecting inside the elbows, or all of the above?

 

[Bondo]

Re: 5.7 Alpha One Gen One Overheating

OK. I assume the elbows are on top of the manifolds. I also assume this can be done with the boat in the water. Should I be looking for a restriction that can be cleared out, or peering inside the manifolds to look for corrosion, inspecting inside the elbows, or all of the above?

Ayuh,... Welcome Aboard,... The areas by the gasket corrodes, 'n rusts, 'n get clogged up...

Cleanin' 'em out, buys a short time, 'n sets ya up to Destroy yer motor when they rot through, dumpin' Saltwater into yer cylinders...

Generally, ya swap on New 1s,....

 

[4ceesuns]

Re: 5.7 Alpha One Gen One Overheating

Is it overkill to simply replace the elbows instead of cleaning them out and reusing? What about the exhuast manifolds, someone I know suggested they should be replaced. I know with an older boat it was only a matter of time before I would get involved in this type of repair. Suggestions appreciated. The boat is basically sound and I will invest in manifolds/elbows as needed. Just want to be pointed in the right direction. Thanks........

 

[Bondo]

Re: 5.7 Alpha One Gen One Overheating

Is it overkill to simply replace the elbows instead of cleaning them out and reusing? What about the exhuast manifolds, someone I know suggested they should be replaced. I know with an older boat it was only a matter of time before I would get involved in this type of repair. Suggestions appreciated. The boat is basically sound and I will invest in manifolds/elbows as needed. Just want to be pointed in the right direction. Thanks........

Ayuh,.... With an unknown history, it's ridiculous to not replace the Whole Shebang, manifolds, 'n risers....

How long have You owned it,..??
Is there any rust creep around the gasket where they meet,..??
It's rotting in toward the exhaust passage the same way,....

Look into the new dry joint exhaust sets,.... I hear they last longer in the brine....