Logo

Mercruiser 170 1986 model wonbt start or hard start when hot

K

Kirk Barrett

Guest
I have a 1986 4 cylinder Mercr

I have a 1986 4 cylinder Mercruiser 170 that will start when cold fine but when I shut it down after the engine has warmed up it won't start and barely turns over. The voltage regulator puts out 13-14 volts when engine is cold but goes up to 17-18 volts as the engine heats up. I don't know if this is just a voltage regulator problem or if the high output voltage is affecting the solenoids and or starter. Can anyone give me any guidance on this. The VR costs $400 and I don't want to just start replacing parts if I don't have to.
 
strange. Sounds like you do ha

strange. Sounds like you do have a volt regulator issue. Never seen high voltage like that ruin anything but bulbs and electronic equipment. I do know that some starters fail when not but not cold. I would start by measuring amp draw while cranking the engine both hot and cold. The tool is readily available at auto parts stores and clips onto the battery cable.
 
"It sounds like your engine ma

"It sounds like your engine may be stiffening up a lot after being run. This can be caused by oil thinning too much. Are you running Merc 20W50 or better, or a good synthetic oil?
It may be constuctive to put a torque wrench on the damper nut and measure the torque required to just start the engine turning, both cold and again when hot. If they are close to the same, then you have an electrical or starter issue as David says.
Rod"
 
"Regualtor is on the fritz. F

"Regualtor is on the fritz. For the $400, Mercruiser has a kit to change to a one piece alternator with bracket and belt. I sent you a few items that I saw on eBay. Hope one works. Guy"
 
"Slow cranking warm 170(47

"Slow cranking warm 170(470)engine is not uncommon. The previous owner of my boat installed a brand new starter and fresh battery, it solved the problem. Your VR problem might be a seperate issue. Measure the voltage at the batt. when its running, your gauge may be off.
Chris"
 
"I have a 170 and the VR went

"I have a 170 and the VR went out - high voltage was causing the motor to backfire. Bought an explosion-proof-rated alternator with regulator from the local auto elec shop for $100. Fabbed a bracket and mounted the alt on the front of the head, aligned with the sheave on the damper. Works great. The motor has always been balky to restart when hot. Maybe the oil. I am using 30 wt non-detergent, per the manual. Should I switch to 20W50? JW in Dixie"
 
"JW:

"I am using 30 wt


"JW:

"I am using 30 wt non-detergent, per the manual."

Which manual? You should switch to a DETERGENT OIL, 15W40, 25W40, 20W50 will all work. Guy"
 
"I just went through this same

"I just went through this same thing,exact same thing last weekend.My voltage regulator is working fine and my gauge was lieing.changed the gauge and voltage is good.
My also started hard when it got warm and found that the distributor clamp was loose enough to let the distrubutor turn while I was driving causing it to retard and start hard
I fixed the timing and clamp down the distributor and it cranks over great ever time."
 
Back
Top