115Yamaha overheating above ±3000rpm

[Bandito]

I have tried just aboud everything but the motor overheats when doing speeds off up to± 17mph have checked base gasket,water tube,salt build up around cylinders,feul starvation thermostats just about everything but water pressure decrease at high revs at telltail.Motor was from 25mm above keel to50mm bellow keel,messured at cavitation plate.Model "84 115 6E5 twins.I have cut the transsom at the keel and starboard motor seems to be better. Prop size(19K s/s.Motors on a 8m/lee cat with centre console.

 

[rickdb1boat]

Re: 115Yamaha overheating above ±3000rpm

Bandito <br />I assume you replaced the Water Pump?? If so, are you sure it was properly keyed to the shaft? That might explain why after you gain speed, it starts to overheat. That's if the impeller is slipping on the shaft.

 

[Harry Blanchard]

Re: 115Yamaha overheating above ±3000rpm

Bandito, I had a similar experience with my 85 and it turned out that the seal around the tube running from the water pump to the head had a seal around it that was worn. It doesn't show up in the parts breakdown and is hidden under a plastic cap at the water pump outlet. Try looking at that, maybe that is the culprit.

 

[Solittle]

Re: 115Yamaha overheating above ±3000rpm

Bandito - I have seen heavy salt water crud build-up under the exhaust cover plate that can restrict the water flow.

 

[ICEMAN]

Re: 115Yamaha overheating above ±3000rpm

I See you mentioned that this is a twin engine set up. Are the motors toed in out out properly. On twin engine set ups, if the two motors are out of adjustment, they can caused a loss of water pressure to one motor or both. The water pressure difference can usually be seen on the guages especially when you turn the boat, one way or the other.

 

[Bandito]

Re: 115Yamaha overheating above ±3000rpm

I just fitted the power head and diagnosed all the possible trouble areas on the motor and leg. The water pump looks OK and the impeller is not slipping! If I open only the starboard motor (that is the one giving problems)and let it labour at full throttle ±12Knots 4600rpm no problem,but i found that as soon as I open both motors full then the water pressure disapear from the teltail,or when I trim up the motor.The motor is currently ±25mm bellow main keel.All I can think is that it is getting cavitated water at the intake and the water is in the middle of the intake at times.Maybe I should cut the keel more at an angle towards the transom,then i<br />could get use off my trim&tilts and maybe solve the problems.I had the motors on a 19 feet mono keel boat first and never had problems only great fishing.MAYBE A BOAT BUILDER COULD GIVE ME SOME ADVISE PLEASE.

 

[Bandito]

Re: 115Yamaha overheating above ±3000rpm

 

[ob]

Re: 115Yamaha overheating above ±3000rpm

Bandito ,If height of water intake is a problem causing pump cavitation from adjacent engine turbulence maybe something along these lines would benefit. <br /><br />low water pickup

 

[Bandito]

Re: 115Yamaha overheating above ±3000rpm

OB thanks,have I only knew you 18 months back I could have saved thoudands on these motors you are the first that make any sense on this.I will try to get hold off that,but with me sitting in South Africa I will propably wait two months for that pick up.But Look forward to that

 

[Bandito]

Re: 115Yamaha overheating above ±3000rpm

Could anybody please tel me where i can get hold of a low water pick up from(porta products)for a yamaha 115 6e5 or any other make it would be greatly apreaceated

 

[rodbolt]

Re: 115Yamaha overheating above ±3000rpm

hello<br /> are theses counter rotating engines?<br /> if so the try switching the gear cases. we see some hulls react differently when the left hand case is on the stbd side.<br /> how far apart are the engines?<br /> did this problem just occur or has it always done this since mounting the engines?<br /> remember that when the hull breaks a plane it is actually rising out of the water. on some hulls with a lot of V it can actually pull the water intakes out of the clean water and cause the pump to lose pressure. also look for any trim tabs or transducers that could be causing turbulence.<br /> good luck and keep posting

 

[Bandito]

Re: 115Yamaha overheating above ±3000rpm

I made some scoops at the water intake and that solved my troobles but i still want to fitt the low water pick ups from porta products or any simalar range I dont have counter pairs on the boat and found that it is the hull that is creating cavatation water