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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4724
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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My friend has an old 90hp 2 stroke outboard,the problem when

Customer Question

my friend has an old 90hp 2 stroke outboard,the problem when you increase speed the overheating alarm sounds,i have checked the carboretters,sparking on all three and the water comes out of the telltale ok wondering what is the next step,it is not oil injection but straight mixure
JA: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else important you think the Marine Mechanic should know?
Customer: not at this time i may change the water pump and give it a good clean in fresh water plus i believe there is a chemical you can use to clear any salt deposits
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Marine Mechanic about your situation and then connect you two.
Submitted: 11 months ago.
Category: Boat
Expert:  Jeff G. replied 11 months ago.
Replace the thermostats and the water pump. What engine is this? Model number?
Customer: replied 11 months ago.
i work in saudi for BAE systems it must be quite old as a friend i am only trying to help as when you increase in speed the alarms sounds overheating,i have checked the carbs and sparks as i thought it may be firing on two cylinders,also jumps when you put it into gear so some adjustment needed there,i believe from looking at it must be a 90's model,the telltale is throwing out a good stream of water but maybe a bit less at full speed, hope this may help?
Expert:  Jeff G. replied 11 months ago.
What brand engine?
Customer: replied 11 months ago.
it is a 90hp mariner
Customer: replied 11 months ago.
it is a 90hp 2stroke mariner
Customer: replied 11 months ago.
it is not oil injection but straight mix in the fuel tank
Expert:  Jeff G. replied 11 months ago.
I'm going to assume it is the 3 cylinder model. The engine serial number will ID it positively for me.If the impeller hasn't been replaced in the last 2 to 3 years I would replace it. Next look at the top back of the cylinder head. The thermostat is located there. If it isn't opening properly then it may provide enough water at slow speeds but not cruse speeds.In the thermostat assembly is also a poppit valve. This is a spring loaded diahram. It opens at higher speeds and water pressure to allow additional cooling. If it isn't opening properly the engine will overheat at higher rpm.Check these and let me know what you find. I'll be out for a few hours but will respond asap.I think replacing the impeller, thermostat and poppit valve will solve your problem and all for under $100 in parts.

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