OhSnap
Petty Officer 3rd Class
- Joined
- May 4, 2010
- Messages
- 77
Hopefully someone can help me with this one! I have some boat experience and 20 years automotive experience, so I have a little mechanical ability but this has me stumped.
I have a 1987 Four Winns Horizon 190, 19' boat with a GM 350 / Mercruiser 260HP with an Alpha One outdrive. It is not a closed cooling system and had a power steering fluid cooler, no engine oil cooler.
Never used in salt water (I was told, and it sure looks good for its age). The engine has overheated at speeds above idle since I bought it last year. I can idle the boat around the lake all day long and it runs cool, but at higher speeds, it overheats within 10-15 minutes and you can smell the exhaust tubes burning. Once, it even blew out the porcelain from the #8 spark plug? but left the metal threaded piece in the head. I believe the engine dieseled and ran backwards after it blew the plug and it shot the drive belts right off the engine and broke one. It appeared there was a little detonation as the electrode on the spark plug was beaten pretty good.
The temp gauge is a little sticky but it works. When the engine overheats is diesels, smells hot and the gauge will shoot up all the way (after I un-stick it). So im sure it is really overheating.
Here is what I have done so far (testing the boat with no improvement between each):
-I removed the hose that comes from the lower unit to the engine and ran the engine and it ran like a garden hose
-I replaced the impeller in the lower unit. The impeller I removed was old and the fins were bent and wouldn't spring back but all the fins were completely intact.
-I replaced the tstat with a marine OEM stat. Other stat may have been original? I had to pry it out in 4 pieces.
-Checked the water flow from the tail pipes. Water runs out of each pipe lightly, like a garden hose at ? volume on each side. There are times when one side runs more than the other. I assume that?s the checkballs for the risers that change this.
-Removed the checkball assembly near the stat housing. It appeared ok, it wasn?t frozen but I wasn't 100% sure what I was looking at.
-I removed and inspected the riser on the starboard side, very little rust inside.
-Replaced the belts
-I replaced the distributor cap, rotor, wires, plugs, water separator and adjusted the timing to book spec.
-Removed the new stat
-Put the new stat back in
-Removed the water pump and took off the back plate. The pump is original (black overspray visible on back plate). The impeller looks good, shaft is intact, bearing is good and it wasn't leaking, so I assume the seal is ok too.
-Opened the petcocks on both sides of the block and poured water in one of the hoses into the engine, the water flowed out freely
The engine runs smooth, just still overheats at higher than idle speeds.
Any advice would be great!
Thanks!
I have a 1987 Four Winns Horizon 190, 19' boat with a GM 350 / Mercruiser 260HP with an Alpha One outdrive. It is not a closed cooling system and had a power steering fluid cooler, no engine oil cooler.
Never used in salt water (I was told, and it sure looks good for its age). The engine has overheated at speeds above idle since I bought it last year. I can idle the boat around the lake all day long and it runs cool, but at higher speeds, it overheats within 10-15 minutes and you can smell the exhaust tubes burning. Once, it even blew out the porcelain from the #8 spark plug? but left the metal threaded piece in the head. I believe the engine dieseled and ran backwards after it blew the plug and it shot the drive belts right off the engine and broke one. It appeared there was a little detonation as the electrode on the spark plug was beaten pretty good.
The temp gauge is a little sticky but it works. When the engine overheats is diesels, smells hot and the gauge will shoot up all the way (after I un-stick it). So im sure it is really overheating.
Here is what I have done so far (testing the boat with no improvement between each):
-I removed the hose that comes from the lower unit to the engine and ran the engine and it ran like a garden hose
-I replaced the impeller in the lower unit. The impeller I removed was old and the fins were bent and wouldn't spring back but all the fins were completely intact.
-I replaced the tstat with a marine OEM stat. Other stat may have been original? I had to pry it out in 4 pieces.
-Checked the water flow from the tail pipes. Water runs out of each pipe lightly, like a garden hose at ? volume on each side. There are times when one side runs more than the other. I assume that?s the checkballs for the risers that change this.
-Removed the checkball assembly near the stat housing. It appeared ok, it wasn?t frozen but I wasn't 100% sure what I was looking at.
-I removed and inspected the riser on the starboard side, very little rust inside.
-Replaced the belts
-I replaced the distributor cap, rotor, wires, plugs, water separator and adjusted the timing to book spec.
-Removed the new stat
-Put the new stat back in
-Removed the water pump and took off the back plate. The pump is original (black overspray visible on back plate). The impeller looks good, shaft is intact, bearing is good and it wasn't leaking, so I assume the seal is ok too.
-Opened the petcocks on both sides of the block and poured water in one of the hoses into the engine, the water flowed out freely
The engine runs smooth, just still overheats at higher than idle speeds.
Any advice would be great!
Thanks!
