New to inboards

jt77029

Cadet
Joined
Apr 12, 2005
Messages
6
I just purchased a 1980 16ft Glastron ssv-168 with a 120hr mercruiser. I have never owned a inboard before and have a few questions about some issues that I am having. The temperature seems to be relatively hot, about 180 at plane and 200 degree and rising to 220 cruising at idle. I don?t know what the normal temp should be but this seems a little hot. The engine starts fine and runs excellent, can rev the engine fine. It goes through the rpms fine. But under load like trying to get on plane, it seems to want to stall. But if I finesse it, it is fine. The overall speed of the boat at full throttle 3900rpm is about 25 miles an hour, that is from the dash gauge but it does seem about right. With this horsepower available, it seems that this small of a boat should be able to go a little faster. Also, coming off plane to idle the outdrive has a whine, that goes away after a min or so. I guess the questions would be: what is the normal temp range, average speed of the boat and why does it seem to lack power? Any help is much appreciated.
 

Gary H NC

Fleet Admiral
Joined
Dec 1, 2005
Messages
8,972
Re: New to inboards

Welcome to the world of I/O boats!
It should be running around 170 degrees,220 is way to warm.
I would bet the raw water impeller is in need of replacing. It may have run hot enough to cause damage.Head gaskets are usually the first thing to fail from running hot.That would explain the loss of top end power.It should run at least 4200 rpm at full throttle in the water in gear..
Don't rev it that much on the trailer!
If it were mine a leak down test on the cylinders and impeller replacement would be first on the list.
Good Luck!!
Welcome to Iboats!!
 

njlarry

Petty Officer 1st Class
Joined
Sep 13, 2005
Messages
330
Re: New to inboards

and also check that your prop is not too high a pitch. Have you got the factory manuals yet?
 

jt77029

Cadet
Joined
Apr 12, 2005
Messages
6
Re: New to inboards

The engine tag says max rpm is 3900-4100. And 220 degrees does not seem hot enough to blow a head gasket. The engine runs great. I haven?t check the gauges to check to see if it is accurate but the engine did seem to diesel at that temp. I did not run it at 220 very long. The 180 is at plane. So what is with the increase at idle? I am not reving it on the trailer, know better. than that. The boat was not used for several years. It doesn?t seem to lack power necessary. It just in the mid range it wants to stall. At high end it runs fine. Thanks for your help.
 

thrasher

Chief Petty Officer
Joined
May 23, 2007
Messages
443
Re: New to inboards

But I think he is correct about the water pump impellor.. It is inside the stern drive and will probably have broken if the engine stood unused for a few years. Once the impellor has broken you will not get much water pumped up to the engine, causing overheating. The poor throttle response is probably due to deposits (varnish) left inside the carburettor from standing so long. If the engine is running, I would suggest adding a strong dose of fuel/engine cleaner to the gas tank and just drive the boat, over a couple of tank fulls of gas it will clean the varnish off and the engine will run as good as new..

Gary
 

Gary H NC

Fleet Admiral
Joined
Dec 1, 2005
Messages
8,972
Re: New to inboards

Its not like a car engine,220 is too warm! At least have the impeller changed.They get brittle,fall apart and plug up water passages.
They should be inspected and replaced every couple years anyway.
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: New to inboards


220 is way too hot.......
Change the raw water impeller as suggested above....
Here is a link for your drive.......
http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf
There are some other things that need to be serviced on your drive if it sat for a few years....
Pull the drive, change the impeller & gear oil & grease the ujoints while it is off........;)
 

jt77029

Cadet
Joined
Apr 12, 2005
Messages
6
Re: New to inboards

Thanks I will change the impeller this weekend.Where is the best place to buy parts?
 

Gary H NC

Fleet Admiral
Joined
Dec 1, 2005
Messages
8,972
Re: New to inboards

You may check with Napa, Or if you have a West Marine in the Houston area
 
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