I have had these same symptoms on 2 engines, old mostly stock 454 and the new 476. With the pump outlet valve all the way open the engine runs at 150 idle and 130 cruising, if I close the valve at all it gets hotter. I have checked everything but the wear ring. Turning the pump over by hand it sounds totally normal, no rubbing or grinding sounds, jet seems to be running fairly efficiently. I pulled the pump outlet pipe off and there was nothing gumming up the hole, can't really see anything. Is this definitely a shifted wear ring? My dash gauge reads 150 when my manifold mounted gauge reads 120, but this is the second dash mount gauge and second sending unit reading the same thing. Is it at all possible that the wire could cause this?? My experience tells me know, but I've seen some weird shit happen before...
what pump are you running? If a berk. style pump, I don't see any way a wear ring could "shift" and interrupt the water flow. If the w.r were to move it would be on the impeller and making noise. As mentioned those temps aren't really anything to be overly concerned with. I am more concerned with my oil temps than water temps. although I monitor both carefully. I trust my mechanical location gages more than elec. gages. What size and type of plumbing are you running? Are you running a t-valve for headers with the ball and spring for idle water control? Maybe it's sticking? Where has the boat been used for the previous years? If in a sandy water area like the lower colorado, such as blyth, yuma etc. the block may be filling with sand and need to be flushed if the problems worsen. Kinda graspen at straws on the last one but just a potential issue/thought. When your gage reads 250+, you can hear the water boiling in the block and it's steaming violently out the dump line then you should get worried.
I figured the old engine had sand in it, but the fresh engine is doing the same thing. It's just a valve at the pump followed by the normal log setup. I also just ultra sonic cleaned my logs and snails and got a crap ton of sand and zebra snail chicks out. I'm not worried about these temps, just curious as to why it's happening. Previously in every boat I have ever had, including this boat when I first got it, with the valve wide open the temp gauges wouldn't even read above 110 no matter what the speed. I guess I should hook up a pressure gauge and see what's up.
well since the old block and exhaust manifolds were clogged with sand and z. muscles it seems safe to assume one or both is also clogging every other item associated with that system so it seems a complete replacement or thorough cleaning of all cooling sys. components, hoses, fittings etc. would be necessary. Maybe the new motor is just tighter and not fully broke in yet and causing more heat from tighter tolerances? Is the new motor turning more rpm's?
Hoses are all new or inspected, logs and snails were sonic cleaned and water runs through them like butter, temperature is at idle and same cruising speed/rpm. I can easily squeeze the pump outlet hose with two fingers, feels like there's barely any pressure. I haven't taken the jet apart, but looking through the intake and hand hole everything looks fine.
the only thing that is the same on the boat is the pump and the outlet valve, and I took the outlet valve apart to inspect it. What kind of direct mount pressure gauge is readily available at lowes or Home Depot?
Good Investment is a small handheld IR temp sensor (Pep boys, Oriellys ect) ,you can use it for a multitude of things like checking oil temp on the pan surface as well as actual block and head temp. The temps you describe are close to what everyone seems to want (but normally cant obtain ) for their Jet I would first verify that the temp your seeing is actually true , if you want it to run cooler you could re plumby running raw water to a T , then into the block , then out of the intake (no T stat) and then to your logs and then the second log nipple loops back to your rizer and finally out thru the tips
pull your bowl and check the area behind impeller. I had a thrust bearing failure that caused overheating from it eating up the area by the water inlet for motor, destroyed the impeller and did not really hear or feel it. I bought the boat apparently with this issue and did not know it
I measured from the water outlet opening to the impeller on two pumps, the one in my boat and one I have sitting in the garage and the distance was the same.
Tanks Tom. I spent a few years of of life carrying one of those around a ship, I probably have one at work I can borrow for a day. I'm happy with the temps, just a little worried that I have these temps with the valve all the way open. I'll just monitor both gauges next week, knowing that the impeller hasn't shifted gives me more of a warm and fuzzy.
Ok so now the only thing that remains of the original package is the logs. Just installed a rebuilt tight jet from MPD. Gauge reads 150-170, local gauge reads 140-150. This is with the valve fully open. If it was running lean it wouldnt heat up so much at idle, the logs must be leaking!?!? Getting exhaust gases into the cooling system of the engine. Season is over for me so by next year I'll have the new exhaust on. My dads boat runs at 110 with the valve closed just a little, raw water lines routed the exact same way. Everything that I changed I was changing anyways, but talk about taking the long road to find the problem.
You are backwards on the lean fat idea. A lean engine will run hotter than a fat engine. As per your'e post over on the dyno section I would fatten it up and see what happens with the engine temp. Keep in mind that fuel in its self is a coolant. M
What I meant to say was that if it was running warmer due to running lean it wouldn't show up so much at idle, which it is. But I am going to re jet and pull the logs to inspect again.
I just read your thread for the first time. I've had several jet boats and they all ran about 150 water temp with zero restrictions. The one time I turned the valve a little closed to get the temp closer to 175 I burned holes in the exhaust tubes linking the exhaust to the transom. Stop comparing to other boats and simply watch your gauges for changes, if something changes then you have a problem.
150 is ideal and normal. Always run it without restriction. You're running logs so you're not trying to get every ounce of power out of it.
Get your engine happy with your jetting. I don't see the point of pulling the logs again.
The majority of production jetboats both thru hull and headers in stock form will typically "barely getting off the cold peg" (100,110 to 120 ) under most circumstances unless restricted in some fashion, having jet issues or running a bypass thermostat system... even on a hot day , mean average seems to be 120 to maybe 140 depending on what and how accurate a gauge is employed and even then the true temp is somewhat erroneous as the water from the jet is only in the block a short time (no circulation or dwell time) , Oil temp is much more important to monitor. In Your case I would recommend that IR temp tester to first establish that you temps are actually what your seeing (or not)
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