rising engine temperature

[handball]

1987 mercruiser inboards 260 h.p. fresh water cooled 800 hours.both engines ran at 170 degrees at cruise speed of 24 mph @ 3000 rpms. starboard engine recently running warmer about 185 to 190 and seems to go a little higher each time the boat is used.water antifreeze mix is topped off, oil full and there is equal flow of salt water from both engines out the exhausts.rises recently replaced and cool to the touch.also checked the screens on the water intakes and found them clean.<br />Also belt on the salt water pump has proper tension.Both engines do not seem to use any significant oil, none added yet.temperature seems to be rpm related and goes down to about 145 when rpm is reduced to about 1500.Seems to me that this would show marginal cooling of the heat exchanger or maybe the loss of a blade from the salt water pump.I would like to check the impeller on this engine but in this case sea ray has put the pump where you cannot even see it no less repair it.whats the best way to replace the impeller and what do you need to remove to do the job?Im thinking I should probably remove the pump to do it, but it is going to have to be done by feel only while laying on top of the engine as it is on the fwd outside on the starboard engine.Today I will remove the end plates on the heat exchanger to see if it is clean.Does anyone have a clue for me as to whats causing this rise in temperature? it is no where near overheating but is heading in that direction.

 

[akriverrat]

Re: rising engine temperature

tstat?

 

[Juancho]

Re: rising engine temperature

Have your exhaust manifold been replaced recently? Exhaust manifolds will last 5 years max in salt water, and that's if you are lucky.

 

[handball]

Re: rising engine temperature

Exhaust manifolds are fresh water cooled, also I have checked the heat exchanger and found it to be clean. also found the screens for the salt water intake to be clean.also have put dock hose in hose to thru hull fitting and blown water thru hull fitting seems clear.I have not checked the thermostat yet but will pick up a new one and change it .

 

[handball]

Re: rising engine temperature

Update on high engine temperature----------------<br />I spent a good part of yesterday pulling off my risers to see what kind of restriction they might have. As it turns out both rises are in great shape and have full water flow. Also changed the thermostat and took her out for a test run. The tempertures of both engines start out the same untill you get to about 2000 rpm the port engine reads about 165 and the starboard is allready climbing 20 degrees higher.When 3000 rpm is reached starboard engine is at 200 degrees, still have the same problem showing restriction of salt water in.So far I have done the following<br />cleaned main heat exchanger, replaced salt water pump, backflushed tranny cooler, checked both rises, replaced thermostat, flushed thru hull with dock hose,checked belt tension on fresh water pump.When inspecting the groco sea water screen I found that the hose going to the salt water pump (wire reinforced) had started to collapse inward so I cut off 3" and reatached it . I think that was my hint for finding the problem.There must be some restriction in the thru hull fitting that allows water flow untill the pump demands full flow, at which time with the partial restriction the hose starts to collapse.There is a bronze fitting on the bottom of the boat with slits in it that are offset from the part that screws into the sea **** so you cannot really get to what might be in the offset area.I have run a knife thru the slits from under the boat and did not feel a lot of resistance like barnicles and such. Today I will try to work the sea **** handle and if it can turn off the water I will remove the hose to see whats what, to really clean this assy I would have to haul the boat or possibly cover the intake with a piece of clear plastic.The other thing I was thinking was to some how plum the salt water intake hose temperarilly to the thru hull for the head overboard thru hull, If I could get that handle to turn on.Any more sugestions would be greatly appreciated.

 

[handball]

Re: rising engine temperature

ALL WORK AND NO PLAY------------------------------Today I took the heat exchanger off the boat and with the end plates off I could flush the small tubes with dockwater and found them to be all clear. also flushed the fresh water side of the cooler it was also clear. took the dock hose and after removing the lines to the risers flushed them out and found no restrictions.I also removed the thermostat put all the lines back together, took her out for a ride and found the problem still there with the engine still running about 200 degrees @ 3000 rpms if I go to 3200 the temp rises even higher.<br />If anyone can think of something else to do I would appreciate hearing from you , as for myself I think I have run out of ideas.<br />Guess I will have to call the local marine mechanic and see if he can figure this one out.

 

[chris in va]

Re: rising engine temperature

It's summer. The water is getting warmer. Still doesn't explain why one engine is running hotter though...

 

[crazy charlie]

Re: rising engine temperature

I have a friend that had a similar problem and did all the same things that you have done.The things he did that you have not are replaced the gasket on strainer,he thought it may be loosing prime.Replaced the hose from strainer to intake,he thought it may be collapsing under higher rpm which causes vacuum on that hose.Replaced entire thermostat housing.He also replaced all risers and manifolds which he said the old ones looked fine.Have your replaced the circulator pump at the front of the motor??He also opened the block drains and ran the engine with a food strainer checking to see what came out of the block.He said plenty of rust and crap came out.He then took a coat hanger and made a 90 degree angle to it and pushed it in the drain to loosen up whatever may be in there.He eventually got the motor right but does not know exactly which cured it.You can also check your sender to the guage by swapping them. Good luck Charlie

 

[ed hobbs]

Re: rising engine temperature

Dang Charlie! I was just going to say "swap the guages" to make sure the problem is not electric.

 

[handball]

Re: rising engine temperature

Charlie,<br />Was your friends engine fresh water cooled? I also replaced the short hose from the intake to the screen housing the other day. I have not replaced the circulator pump as I can see good movement with the cap off the heat exchanger . A mechanic I know told me to replace the guage and sender just to make sure it really is running warm, I will pick up a new pair today and replace them , the guage I have now is a teleflex and there is no marked numbers between 170 and 220 so you have to guess what the temps really are. I am going to buy the red series teleflex that has a 200 degree line to replace the one I have.<br /><br />My mechanic friend also reccomended I replace the heat exchanger with a new one for about $500, I would never do that without first switching exchangers with the port engine. Another mechanic reccomended I bring the exchanger to a radiator repair guy to boil it out, that I might do.I wish your friend could say what he did to fix his engine.Another thing I might try is to drain the fresh water and antifreeze from the block and replace it with plain water and rust preventative, as I understand plain water is a better heat transfer then a mix of anti freeze and water. I hope it is as simple as replacing the guage and sender but I really dont think it is as both guages start out rising the same untill the rpms get to 3000. There is a gadget on the market that reads temperatures on a digital scale put out by a company called dytec and sold at napa stores it cost $100 it would be real interesting to compair readings of blocks manifolds, rises etc. with the port engine.Another thing that is true is the water temperature in the sound has increased about 30 degrees since spring, but it has no effect on the port engine.Last week I took a 300 mile trip up the hudson river and as I did I saw the outside water temp going up and the guage reading going up slightly It seems to me that this shows something is marginal in the cooling system.I dont give up easily but this one has me baffled, pretty soon I am going to run out of Ideas.

 

[MarkJSullivan]

Re: rising engine temperature

You must be driving your passengers crazy!!!! Let it run hot for the rest of the season, watch the gauges, then leave it to a winter project. You have 2 engines, so you will get home..I find talking boats is like talking golf..soon enough nobody cares and the fun is spoiled...

 

[crazy charlie]

Re: rising engine temperature

Handball,my friend had the same set up that you have except his was older.I asked him what he thinks was the ultimate problem and he thinks it was the seawater pickup and the hose to it.He said it looked fine when he finally got the impeller out but he replaced it anyway and noticed a difference.He said a lot of rust and crap came out of the block when he ran water through it and opened the drain and fished around in there with a coat hanger.He also replaced the thermo. housing.Good luck getting to the sea water pickup but it needs to be done.I would never recommend continuing to use the boat that way.The people that do that wonder why their boat burns oil and why they eventually break down.How could this happen to me they say????These are the same people that when the temp. gauge rises they go faster to get where they are going quicker. Charlie

 

[MarkJSullivan]

Re: rising engine temperature

sorry Charlie...good point...I was being irresponsible...it just seemed that for 20 degrees he was ruining his summer and it could wait until a full winter project

 

[boatingfool]

Re: rising engine temperature

I have a fresh water cooled volvo that is having the same problems.<br /><br />I have changed the water pumps,fresh & raw.<br />Didnt help.<br /><br />I changed the thermostat.<br />Didnt help.<br /><br />I pulled the heatexchanger and cleaned it out.Some small debris; pebbles ,a weed or two.<br />Didnt help.<br /><br />Removed thermostat and ran with out one.<br /><br />IT HELPED!!<br /><br />The engine went from running 200 - 210(then I would have to stop and let her cool off)down to 175- 180. <br /><br />That was about 2 months ago.<br /><br />But since that day, everytime I take her out she runs a little hotter .She is back up to running at 200. <br /><br />I'm lost.

 

[crazy charlie]

Re: rising engine temperature

Boatingfool,be very careful!!!! Every manual I have ever read all say NEVER run without a thermostat.Since your temp went down right after you removed it you know it is a flow problem.Look carefully at the passages in the thermo. housing.Open the brass plug on the riser while running and see if the water shoots out or dribbles out.A coat hanger works wonders on clogged risers. Charlie

 

[handball]

Re: rising engine temperature

charleeeeeeeeeeeeee I found the problem and am almost embarest to admit what it was.The thing that fooled me was that both gauges acted identicle as the engines warmed up untill about 3000 rpms. IT WAS THE GAUGE OR SENDING UNIT-------<br />I replaced them both with new teleflex units and for about $45 all my troubles for now are gone. The engine now runs at 180 degrees at 3400 rpms.<br />I guess that going through every thing up to this point at least gives me some piece of mind knowing what kind of condition every thing else is in. These 350 mercruisers run beautifully and still look like almost new I would not take any chances overheating them and ruining them.I have always been bothered by things that are just not right and dont stop untill I can correct the problem.Thanks to all you fellows who tried to help with this problem I really appreciate it.

 

[crazy charlie]

Re: rising engine temperature

Handball Good news!!!Now you have piece of mind and new guages.I guess thats why the professional mechanics that really care about their customers recommend to check the simple and obvious things FIRST.My friend has sold his boat since,it was a 78 formula with the orig. motor.He sold it to a mechanic who had every intention of repowering it.This was 2 years ago and it is still going strong.the new owner said he ran full throttle all day last weekend trying to MAKE a reason to replace the motor.He just cant kill it.**** good motor!!!! SEE you on the Great South Bay. Charlie