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View Full Version : 1998 Pro star LT1 over heating issues.


Sloz06
09-02-2009, 12:04 AM
Heres the story.

A purchased a boat 3 weeks ago, before buying, test drove the boat for about 25 minutes,
after some full throttle and cruising I came to a idle, went to accelerate. and engine "safety" wouldn't not let RPM's rise" Temp Gauge started to pin let the boat idle back to the trailer.
engine was VERY HOT .


Took A Gamble . Previous owner, was asking 8500, and he took 5500 AS IS.

Brought the boat to my shop, and started my diagnostic dissecting

First i checked the impeller. "looked new and seemed to be pumping "garden house" water through intake house quite nicely.

started taking each house off coolant system, and found a lot of crud "rust" gunk in manifold drains, block holes ect. Cleaned everything out and replaced thermostats"both".
Ran bought for 30 minutes everything seemed Fine.


Put boat in at my lake and have at least put 20 hours on boat with only 2 sign of first engine hesitation"stall" after heavy use of boat.

PROBLEM TODAY!!!!
My brother Pulled me skiing roughly 6-10 minutes of 36 mph "3400 RMP"

after 2 passes I dropped and rested. 3 minutes later he went to pull me up and same problem with engine NOT GOING.

brought RPMS up with TRANY not engaged and saw temp drop 30-40 degrees.

Have done a bit of reading and talked to a few people and i guess this is a known problem with the LT1 engine. Any quick fixes to ride out the rest of the summer" this winter I can do further work.

ANY HELP GREATLY APPRECIATED.

D3skier
09-02-2009, 12:19 AM
have you done a search on here? I've found many threads regarding this and did a search from here...type in for search LT1 overheating

http://www.google.com/coop/cse?cx=005775850323706454504:8-nmuizykqo

jakethebt
09-02-2009, 08:05 AM
I think this will help.

http://www.mastercraft.com/teamtalk/showthread.php?t=31626&highlight=overheat

billr
09-02-2009, 09:27 AM
You might want to check your water pump to see if it's leaking.

Thrall
09-02-2009, 10:15 AM
Check for any obstructions in the raw water screen (in the trans cooler).
Replace BOTH thermostats, make sure the upper 160 deg is lt1 marine specific with the hole drilled in it.
Replace impeller. (if it looked good, but pulled the temp down with increased flow, no load on engine, it coul be soft and not pulling water like it should)
Check that it has the mods for teh water vent line(s) coming off the heads, being a 98, it should already be set up like that.
Make sure none of the hoses are collapsed, especially the rw intake hose.
There's alot of info on here, do some searches.

That said, you seem to have got a screaming deal on the boat (unless it's beat up real bad and has 2000hrs on it). I wouldn't take double that for my '96.

Ski-me
09-02-2009, 11:48 AM
Check for any obstructions in the raw water screen (in the trans cooler).
Replace BOTH thermostats, make sure the upper 160 deg is lt1 marine specific with the hole drilled in it.
Replace impeller. (if it looked good, but pulled the temp down with increased flow, no load on engine, it coul be soft and not pulling water like it should)
Check that it has the mods for teh water vent line(s) coming off the heads, being a 98, it should already be set up like that.
Make sure none of the hoses are collapsed, especially the rw intake hose.
There's alot of info on here, do some searches.

That said, you seem to have got a screaming deal on the boat (unless it's beat up real bad and has 2000hrs on it). I wouldn't take double that for my '96.

Agree....check your thermostats. My LT1 did the same thing and later found out I had an automotive 185 stat. If yours is similar to mine, the lower stat is a 142 and the upper one is 160 with a hole drilled into it. Good luck and let us know how it goes. Sweet deal on your boat, too!:cool:

Sloz06
09-02-2009, 10:11 PM
Hey thanks for your quick reply's


right now i have 2 160 thermostats auto part ones. the Correct Ones are on order now. and should be here any-day. but the problem is summer is not waiting... and coming to a quick end.

Am i doing Any kind of damage to the engine. it doesn't seem to get super hot

and only happens once we stay at a constant speed of 36 after 2 passes up and down the lake.
coming to a stop and then go for another run. thats when if we get the RPM limiter.

today after checking the tube that connects the blocks for any blockage.I found a constant leak coming from the shaft for the water pump."could this be a source of an Air pocket?
whats leaking, what do i need to do repair this ? should I continue using the boat for a few more weeks and fix the leak come "winter months?"
the boat only has 280 hours on it.

JimN
09-02-2009, 10:49 PM
Hey thanks for your quick reply's


right now i have 2 160 thermostats auto part ones. the Correct Ones are on order now. and should be here any-day. but the problem is summer is not waiting... and coming to a quick end.

Am i doing Any kind of damage to the engine. it doesn't seem to get super hot

and only happens once we stay at a constant speed of 36 after 2 passes up and down the lake.
coming to a stop and then go for another run. thats when if we get the RPM limiter.

today after checking the tube that connects the blocks for any blockage.I found a constant leak coming from the shaft for the water pump."could this be a source of an Air pocket?
whats leaking, what do i need to do repair this ? should I continue using the boat for a few more weeks and fix the leak come "winter months?"
the boat only has 280 hours on it.

You have aluminum heads and they don't like being overheated. Make sure all of the hose clamps are tight. I wouldn't bother with a screwdriver- use a nut driver or a 1/4" ratchet with a short extension and a 5/16" socket. If your water pump is leaking, it needs to be replaced. Which pump- raw water or circulating? Id you have a water pump leak, I would fix it. Running it hard while it's leaking could cook your motor.

Ski-me
09-03-2009, 12:53 PM
Aren't the water pumps suppose to leak a little to indicate the need for a replacement? Kinda like an automotive pump.....leaking at the weap hole indicates the pump is wearing out and needs replacement. I'd recommend replacing the water pump.

Does your top 160 stat have a hole drilled in it? That is necessary for the LT1.

Here is my original thread on this problem when I first bought my boat....

http://www.mastercraft.com/teamtalk/showthread.php?t=23352

Jorski
09-03-2009, 12:59 PM
+ 1 for checking out the circulation pump...make sure that your boat has the correct one as the LT1 is reverse flow cooling.

justinglow
09-03-2009, 01:01 PM
A 1998 with only 280 hours for $5500?? Man you got a killer deal even if needs work to make it right!! Good buy.