4.3 YAMAHA I/O OVERHEATS

[mobiletech]

Engine overheats at cruising speeds. Does not overheat at idle or when going very slow. Any advice would be helpful. After cruising for about 4 or 5 min temp will go well above 175 when stopped and let idle temp will fall back to around 125 or less in about three minutes.

 

[Mod2]

Re: 4.3 YAMAHA I/O OVERHEATS

Mobile...moving your post to the I/O Troubles and Repair forum.

 

[Capt Ken]

Re: 4.3 YAMAHA I/O OVERHEATS

One of two things can do that. Either the water pump impeller needs changing or the risers has rusted up and not allowing water to exit the engine. To check the risers, remove the top hose on each riser and connect a garden hose. Turn the hose on and there shouldn't be much of any back pressure. If back pressure is present, then you've located your problem. Next problem is, there ain't no riser to be had. They're suppose to start recasting them in sept, but no firm dates as of yet.

 

[mobiletech]

Re: 4.3 YAMAHA I/O OVERHEATS

Followed Capt Kens advice. Checked risers with hose and they flow very well. Removed raw water pump impeller. Impeller is very much like new. None of the vane are hard, missing or distorted. I failed to mention that I got this thing out of the shop the day before overheating. Had to have shifter cable and those bushings cleaned up in lower unit to have smooth shifting once again. The guy who did the work does almost all of the sterndrive repair work in this area and is very proficient with the yamaha unit but I guess there is always room for error. I am taking it back to him tomorrow to see if he can figure it out. I think and a few others agree that I must be getting air from around a seal or o ring somewhere. If anyone has run into this i would appreciate the help. By the way, just wanted to give an extra thanks to Capt Ken for taking the time to talk with me today. Super nice guy.

 

[Capt Ken]

Re: 4.3 YAMAHA I/O OVERHEATS

Anytime

 

[mobiletech]

Re: 4.3 YAMAHA I/O OVERHEATS

Took boat back to repair shop yesterday. The guy said he pressurized the water intake system and found no leaks there. Put a new thermostat in it and freed up some bypass plate in the upper t/stat housing that had rusted up. Took it to the water and once again it overheated when getting up on plane------soon as I back out of throttle to idle it cooled back down. Repair shop is suppose to take it to water today and see if they can find any hoses collapsing. If not I guess they will pull the outdrive again and check for any mistakes there.

 

[mobiletech]

Re: 4.3 YAMAHA I/O OVERHEATS

Thank God. Boat is finally fixed. Repair shop found impeller vanes had worked through hose to powersteering cooler screen and at high rpms engine was starving for water. Previous owner must have had an impeller come apart and did not find all of the pieces.

 

[jsharrow]

Re: 4.3 YAMAHA I/O OVERHEATS

Where is the impeller on the Yamaha 4.3? We bought the repair kit, but don't know where it is. I guess we should alos buy a shop manual? I heard it wasn't too hard to replace the impeller. Please tell me where it is. Thank you.

 

[Capt Ken]

Re: 4.3 YAMAHA I/O OVERHEATS

Its a trade secret. If I told you, I'd have to send Rocko and Lefty to visit you and make sure you would never talk again. Go check your other post, I answered it there.