Engine Overheating Problems

[conradg]

I have discussed my problems in the general section of the forum but think this is the appropriate place to continue.

I have an AS Pro 2002 whic I bought about 6 weeks ago. I have had ongoing issues with seeming sporadic engine overheating. Here is the background:

- Marine Power 5.7l engine with Raw Water Cooling
- From condition of boat and trailer it appears to have always been used in fresh water
- I am using the boat consistently in Salt Water
- After every use I disconnect the hose going from the strainer to the pump and flush with garden hose under gravity (no household water pressure applied). At idle hose supplies more than enough water as it overflows.
- I have a new 140f thermostat installed which I did based on reading many posts on this forum. It originally had a 160f thermostat when I got it. It runs at about 160f with the 140 thermostat.
- I have dismantled and checked the entire cooling system from the pickup to the raw water pump and am confident that there are no air leaks and that the impeller is ok.

I have worked out that the overheating occurs after the boat has been running for a while and then is switched for probably at least 10 mins. Continuous running seems to be ok but sometimes when trying to teach someone to ski, the constant acceleration and then idle can cause the overheat. On starting after a greater than 10 min break, the temp slowly starts to rise to the maximum and the only thing that fixes is it to get the boat on the plane. The temp then rapidly returns to normal.

On occasion when the temp indicates max, I have noticed what looks like small bursts of steam coming from the back of the boat.

I normally have no problems when flushing but yesterday it started overheating at idle. Obviously not being able to get in the plane, I thought the only solution would be shut it off but I decided first to try squeezing some of the cooling hoses. When I gave a few pumps on one of the hoses leading from the thermostat to the manifold, all of a sudden the temp rapidly dropped back to normal. I noticed a cloud of steam from the exhaust a few seconds after the return to normal.

I'm going to remove the other hoses and check them.

I have written this long post in the hope that more detail will help someone to recognize this specific problem. This is driving me nuts but it never seems like the engine is actually overheating. Obviously I could be totally wrong!

I am convinced that a build up of steam is happening in the top of the engine when it is switched off and it needs something to happen to push this out of the engine before it will indicate a temperature drop. I recall my cousin being warned about running his Nautique in salt water due to potential for boiling to occur and consequent damage to aluminum heads.

[Midskier]

did you replace the impeller?

After every use I disconnect the hose going from the strainer to the pump and flush with garden hose under gravity (no household water pressure applied). At idle hose supplies more than enough water as it overflows.

unless you have an unusually high volume household supply it sounds like your impeller is shot.  if you have to bring the boat up to any speed above 15mph to get the temp down the impeller is NOT doing it's job the PROPELLER is doing the work - bringing the boat to speed will force water up the water intake grate.

engine temp will rise after the engine is turned off because there is no source to cool it.  turning the engine back on the impeller if still functional should easily bring the temp back to normal without having to move the boat or bring it up to speed.  I think I have posted a few impeller pics in the gallery bad impellers are not always obvious. 
or maybe you have a good impeller just not the right one.

Dan T

a call or e-mail to me or Ron T and we'll help you get cooled off

[Joel]

Listen to Dan Da Man!!!  Definitely the impeller...  easy fix & relatively cheap compared to EVERYTHING else that could go wrong.   

Joel

[conradg]

Ok guys I'm listening.

The previous owner told me he had replaced the impeller just before i bought the boat and so I was assuming all was ok with the impeller. I found a blister pack in the boat which had the old impeller in it which I assume came from the new impeller. On initial checking of the numbers on the pack I am starting to think they put the wrong impeller in. I recall reading somewhere that an incorrect one may work but not provide enough pressure or flow.

I have the Jabsco pump number 22110-0201 but am battling to find the correct impeller for it. Can anyone help?

The label on the blister pack reads:
J53-555
KIT Impeller Neoprene
13554-0001-P

But as mentioned I think that is the wrong impeller.

Assuming the impeller is the problem I can see how the symptoms match your guys explanation.

Thanks again to Dan and Joel for all your help. I really appreciate it.

[RonT]

The impeller that belongs in there is a Jabsco 18777-0001 $39.95

[RonT]

The impeller that belongs in there is a Jabsco 18777-0001 $39.95 kit
I don't recognize the part numbers on the blister pack you have, maybe a Johnson number or aftermarket.
Another cause I have seen is running too wide of an impeller wearing the end plate & inside wall, then replacing with the correct impeller after the damage is done & now there is clearance at the ends causing min. pumping at idle. 

[conradg]

Upon further research I have discovered that current installed impeller (incorrect one) is only 1 29/32 inches deep (according to Jabsco data sheets). Correct impeller as suggested by Ron is 2 inches deep. This would mean there is currently an air gap in the pump between the impeller and the pump walls which I think would explain the less than designed water pressure.

I have ordered a correct impeller from local supplier in Oz. I will install and test this weekend.

[conradg]

Good news! I put the correct impeller in and ran the boat twice since then and all my overheating issues are gone. She runs perfect now.

I actually discovered that the 2 previous impellers where both wrong. There was an old one lying in the boat. The previous owner must have just matched up to the impeller that was in the pump but this was the wrong one originally.

A big thanks to Dan, Ron and Joel for being so insistent. This forum is great, not sure what I would have done without it.

Cheers,
Conrad.

[conradg]

Something else I did which may be of interest to other saltwater users is that I added in a home made garden hose flushing facility.

I put a T joiner in the coolant inlet hose between the strainer and the oil cooler. Connected to the T is a valve and then a quick connect hose fitting to connect my garden hose. Under normal operation the valve is closed. For flushing, I connect the garden hose, open the valve, turn the hose on and with the engine off all the water pushes backwards through the strainer and out the water intake. Once the engine is running the coolant pump just sucks as much as it needs and the excess goes out the water intake. You can see if the engine has enough water just by making sure some water comes out the water intake under the boat. The T piece is below the level of the strainer so there is no chance of pump priming issues. Also the garden hose does not pressurize the cooling system as any excess water that the coolant pump does not use just goes out the water intake.

The garden hose pressure in Australia must be higher than US as at idle, it supplies more water than the coolant pump needs.

Anyway it makes those late night cleaning sessions a lot easier. It's summer here and Saturday night we were flushing the boat at 11 at night. Had to get the best water just after sunset and then some evening drinks. Thank god for great silencers.

I think the neighbors are probably cursing the day I bought the boat but I am sure they will get over it!

[RonT]

That's exactly where I place the "Tee" on my installations, the deluxe install includes a hose extension to the transom & a stainless fitting with a cap & threads for a garden hose to connect to right at the transom. This system with 3/4" garden hose with good pressure is good for about 1000 rpm, above that you will begin starving the pump.