Engine overheating at idle

[davidson12]

Hello everyone,

The engine on my 88 Mariah has been overheating when at idle/crawl.
I put in a brand new thermostat that didn't solve the problem, still overheating. It's strange because when I'm cruising at a good pace, the engine cools down rather quickly which makes me think that my water pump or impeller is shot. Thoughts? Also -- can anyone suggest a good place online for replacement parts? I've got a Ford 351 engine.

[davidson12]

Okay -- did a search and found another thread with the exact same issue. It looks like a bad impeller.

[88MariahATX]

http://www.skidim.com/ will have everything you will need. Do you have a filter at the raw water pick-up? Could it be clogged? Have you changed the impellar latley?

[davidson12]

http://www.skidim.com/ will have everything you will need. Do you have a filter at the raw water pick-up? Could it be clogged? Have you changed the impellar latley?

I'm not sure if there is a filter at the raw water pick-up. I don't think it should be clogged, the lake that the boat is in has no weeds. I've never changed the impeller, it's the original.

[mapleleaf]

its time for an impeller.......life's nice cruising at idle.....

[wotan2525]

I at least check the impeller every spring and always keep a spare one in the garage. Easy/cheap way to avoid missing out on a weekend.

[rludtke]

I just ordered a replacement impeller for my 1987 TS6M from Skidim. I plan to replace the thermostat too.

My engine never registered high temps on the gauge, but I noticed the under cowl temps seemed unusually high when I lifted the cover. Then I had difficulty starting the engine, and had to use wide open throttle to do so. My suspicion is that the impellor may have come apart and sent pieces downstream to clog the exhaust cooling passageways. My theory is that the high exhaust temp was causing vapor lock in the carb.

This happened on the last run of the season, and I promptly put the boat away without investigating. So I haven't torn the pump apart yet, but will soon. I may need to pull the exhaust apart too, to inspect for debri.

Anybody else run across this problem?

[purple boat]

I haven't run into the high temps, but if you are going to pull the exhaust manifolds, let me give you a word of advice: use penetrating oil on the mounting bolts for the manifolds and risers. Liberal amounts. Let it sit and soak for a couple days. Apply more oil and let it soak some more. When I pulled mine, I broke 4 bolts from the manifolds to the risers, 1 from the head to the manifold on one side and stripped the heads of 3 bolts from the head to the manifold on the other side. An afternoon of work turned into a month of not being able to run the boat. What a pain in the hindquarters. I replaced the manifold to riser bolts with stainless but cannot find allen head in stainless in the right size to go into the heads. If anyone knows where I can get them, please let me know. And use more penetrating oil...

[87SunSportMikeyD]

Holy crap!!!! Thanks for letting me know!!

[wotan2525]

I haven't run into the high temps, but if you are going to pull the exhaust manifolds, let me give you a word of advice: use penetrating oil on the mounting bolts for the manifolds and risers. Liberal amounts. Let it sit and soak for a couple days. Apply more oil and let it soak some more. When I pulled mine, I broke 4 bolts from the manifolds to the risers, 1 from the head to the manifold on one side and stripped the heads of 3 bolts from the head to the manifold on the other side. An afternoon of work turned into a month of not being able to run the boat. What a pain in the hindquarters. I replaced the manifold to riser bolts with stainless but cannot find allen head in stainless in the right size to go into the heads. If anyone knows where I can get them, please let me know. And use more penetrating oil...

I wouldn't use stainless bolts if I were you.... stainless gets even more brittle when heat cycled and isn't rated for the correct torque specs. It sounds like the person that installed these manifolds didn't use the correct anti-seize when installing them -- that would have avoided all of your issues. I've had my risers on and off a few times (or more!) and have never had any issues. I stripped one head bolt when reinstalling but otherwise.... knock on wood!

[purple boat]

I think the main problem was that the manifolds had not been removed for at least 10 years. Can't say I blame the previous owners for not removing the manifolds for a long time; I wouldn't have tried removing them except I saw evidence of some slow leaks between the manifolds and risers. When I pulled the manifolds (finally) I found long, deep cracks in the bottom of both manifolds (couldn't see the cracks while installed). A friend and I welded them up, repainted them, and put them back on. Look good a year later, and no leaks. Lot less water in the bilge too...

[rludtke]

I replaced the impellor and the 140 F thermostat this weekend. The old impellor was all in one peice, which is good. I decided I didn't need to keep digging into the exhaust. I ran the engine on the hose- temps stabilized at 150 F, and quite a bit more water was noted coming out of the exhaust than the last time I ran it on the hose, so I think I made steps in the right direction.

My carburator has given me fits off and on ever since I purchased the boat, and I may have stumbled on to why...

I have always had occasional flooding problems, which would often prompt me to remove the bowl and adjust the float level. It did it again this time, and several trys could not get it to settle on the right float level. So i remove the needle and seat for inspection, and found debri. Clean, reassemble, and try again. Still flooding. Tear apart, find more debri, try again, still flooding. This went on several times, until i decided to have a look at the inlet screen. My screen was intact, but not fully secure, and could lift away, allowing junk to pass which would hold the needle valve open and cause flooding.

I think I finally found the root cause to my intermittant problem. I plan to add an inline fuel filter down stream from the pump, right before the carb inlet. Hopefully this will cure this issue.

[brack]

I ran accross the same problem.....along with a bunch of rust breaking loose in my risers when i first bought it ( she sat for a few years...FEW )....the impeller broke apart and all of this plugged up the exhaust and this was the root cause of the exhaust hose burning.......