will wrong pitch prop cause overheating?

[MEM]

i have a 16ft. deep v-bottom walk-through windshield.it has a 13x19 prop on a 85 hp motor.my max rpms are 4,000-4,100.it comes out of the hole fairly well,not great.water temp coming out of pee hole and outlet is to hot to hold my hand in for more than a second or two.much hotter than my friends boat.can this prop be lugging the engine causing this slight overheating?thanks!

 

[Down South]

Re: will wrong pitch prop cause overheating?

How long have you owned this boat and have the rpm always been this low? What brand motor and year model is it? Most motors min WOT rpm range is around 4500 or above. 5000 rpm or a little above is a good figure to shoot for. If your motor is running well, I'd say you are over propped. It's possible that the motor will over heat in this situation. Do you have a high temp alarm and if you do, is it coming on? Anyway, you need to get the WOT rpm up. You may need to go to a 13X15 prop by looking at the info you gave. Is there anything else you can tell us about your problem?

 

[DJ]

Re: will wrong pitch prop cause overheating?

MEM,<br /><br />That is too slow-no matter which flavor O/B you have.

 

[Spidybot]

Re: will wrong pitch prop cause overheating?

Your cooling system will cope with some excess heating. If the balance between heat buildup and cooling system capacity is not maintained, your motor will run too hot. Your cooling capacity relates to the impeller and/or thermostat (and free waterways in the cooling circuit).<br /><br />I'd suggest you test the boat with minimum load. For comparison, my SeaRay 16 with Merc 115 originally came with a 19 pitch. Worked alright but went pretty high in rpm and had problems dragging air when turning or trimming out the motor. Swithed to a stainless HighFive and went up to 23 pitch to get best possible mileage. I'm still within WOT range and has a top speed under best conditions of 53 mph.<br /><br />As a rule when calculating rpm, one inch up or down in pitch makes a change of 200 rpm (higher pitch = lower rpm).<br /><br />For checking you may visit Mercury's site and click Propeller Selector. This will give you an idea.

 

[MEM]

Re: will wrong pitch prop cause overheating?

its a suzuki dt 85 has new t-stat and head gasket.overheat alarm came on once ,which along with very clean white plugs ,induced me into the head gasket swap.what should the water temp be coming out ? i have looked every where and can't find the answer.i know the stat opens at about 111 deg.i will measure it this weekend and find out exactly how how the water is.thanks for the input.

 

[Mumblerone]

Re: will wrong pitch prop cause overheating?

I do not believe a prop pitch can overheat your engine.(non-racing etc.) I would look elsewhere, something to do with your recent repair. Blockage on water circulating through engine. I've never had water coming out hot. Is it a good stream of water. Does it over heat at idle or just WOT. Which is low, should be closer to 5000 rpm's. Be careful, you don't want to do additional damage.