Running hot at troll speed

[tugboat80]

I have a 92 15hp J15RENM. I freaked out when it started showing steam when the weather changed so took it to a marine shop. Tech repalced water pump and advised me that the prop shaft was straight. I was concerned because previous owner had hit a log. Tech also stated that I have a very fine engine with much life left if taken care of. I had fogged it for winter but today was so nice at 40+ degs and sunny so I took it for a cruise. Had some smoke at first then it ran like a dream. Smooth vibration, purring at wot, trolling 1.7 mph clean as can be. Then it changed slightly so I poped the hood and felt the thermostat housing: Too HOT to touch. HOT HOT. I let cool awhile then started, ran at wot for a mile, then felt the head: warm as normal, three second test. Water temperature reported at 45degs. At troll speed the tell tail is not strong, at plane speed the tell tail is strong. Is it normal to run hot a slow speed?

 

[Rick.]

Re: Running hot at troll speed

Did your mechanic change the entire pump or the impeller only? Sounds like perhaps your pump housing might be worn. Best of luck. Rick.

 

[raczekp1]

Re: Running hot at troll speed

if you trol at salt water there can be some salt products at termostat, chead chanel, and under head(around cylinder bore). water jacket can be also blocket.
try to check termostat-ts only 3 bolts at uppwe part of head.remove termostat, clean and try termostat at glas of hot water.

if you trol a lot and block operate at higher temp water pipe gromets, located under powerhead can start to swalow and block water entring powerhead.

if mator will be mine I would tear powerhead, change this gomets.

here is good link:
http://www.sschapterpsa.com/ramblings/water_circulation.htm

 

[tugboat80]

Re: Running hot at troll speed

My tech has offered this explanation: At low rpm the t stat is restricting water in order to heat up the engine. The needle bearings of the crank are required to expand to avoid chattering and peening the shaft journals. At higher rpm and more heat production the t stat is bipassed so the engine will not be as hot. The sound of my Evenrude 4.5 concurs with this theory because with no tstat it rattels some at low speed then quiets down at higher load. My next move will be to get a heat gun or what it is called to check temp while trolling. I like this engine. Light and powerful.

 

[Rick.]

Re: Running hot at troll speed

My tech has offered this explanation: At low rpm the t stat is restricting water in order to heat up the engine. The needle bearings of the crank are required to expand to avoid chattering and peening the shaft journals. At higher rpm and more heat production the t stat is bipassed so the engine will not be as hot. The sound of my Evenrude 4.5 concurs with this theory because with no tstat it rattels some at low speed then quiets down at higher load. My next move will be to get a heat gun or what it is called to check temp while trolling. I like this engine. Light and powerful.

Never heard an explanation like that before. By your description, it is running way too hot at trolling speed. What did your mechanic say about that? Does he think it is normal? What your looking for is an infra red temperature reader, I think. Rick.

 

[ob]

Re: Running hot at troll speed

Get yourself a 163 degree temp stik. Dealer should be able to provide you with one. Mark the T/stat housing and block and test run. If the marks melt it's overheating. You can also just apply the temp stik to areas while testing and see if it melts.

 

[tugboat80]

Re: Running hot at troll speed

I asked tech "how hot is too hot?" he said "couple hunderd". I ordered a infrared temp gauge, will test under way. Has anyone had to alter a t stat or run without one. Tech had replaced water pump last month and I immediately noticed lower water flow from tell tale at low rpm. Hoping reassembly was done correctly.