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Discussion Starter #1
Hello guys, I have a problem with my boat and have a question for ya! Long read but please bear with me!:bangmyhead: :wink2:

First off, I have a '75 18' Riviera speed boat with a 455 olds and a Berkeley JC pump. The other day while out on the river, as I pulled out onto the river from the bank I sucked something up from under the water into my jet (nothing new and happens from time to time on our river). I tried to get on the accelerator and that's when I knew I sucked something up, no forward power and was starting to overheat! I shut it off and turned it back on and it was still plugged, so I shut it off and went under the water to see if I could feel anything in the intake but I couldn't! So, while attempting to get back to shore, I would romp on it a few times on the way to clear it out and finally it seemed to break free and my power was back!! Only problem this time was on the way back to the boat ramp after that, my temp would fluctuate quite a bit, from 160 to 210 and back all the way to the ramp!!

Now, I have this thermostat kit from Rex Marine Chevy / Olds Thermostat Kit - Aluminum: Automotive Performance Products, Boat & Marine Parts & Hardware and have been running it for 6+ years now without a problem at all before this so I know that it's plumbed correctly. It has a 160 deg thermostat in it and my boat usually runs at 160 +/- 5 degrees which makes for a pretty boring temp gauge to look at normally! But after this last plugged pump problem, the boat runs like it normally does for power but the temp gauge is having a seizure with the temp fluctuating, which it never did before!!

So when I got home and looked in the intake grate, it was perfectly clear with absolutely nothing foreign in it. So figuring that it was time for a new thermostat since I was still on the original 6+ year old one, I ordered a new 160 replacement from Rex Marine and installed it!! Also hosed out every hose going in and out of the block to make sure water flowed like it should and no foreign matter was in anything which it didn't seem like it was!! Everything looked good to go.......until my next outing!

I took the boat out yesterday, and as soon as the boat got up to 160, it kept going!! It was doing the same thing as the other thermostat did, going from 160 to 210 and quickly back down to 160, just to repeat itself all over again! If I went less RPM, it didn't go as high, but around 2500 rpm or so it would get all the way up to 210 and quickly drop back down!! Intake for the pump is still clean, and all the hoses flow great with no obstructions, and since the boat heats up to a point and then quickly drops I'm pretty sure the thermostat is working correctly (and yes the plastic divider and spring are installed with the thermostat and housing in case someone was wondering!:D)

But here's the kicker! When I run the boat in the driveway with a garden hose and a hose splitter (I have the splitter giving most of the water to the motor and a little to the pump to see some water come out of the jet), I can run the motor for the same amount of time at 2500 rpm or so like on the water but in my driveway with the hose and the temp stays like it should at 160 with no fluctuation like normal!!

So............. my question is this!! Since if I can supply water to my motor by the hose which bypass's the pump completely and it runs a perfect to me temp but as soon as I run it like normal in the water with the pump supplying the water, the temp gauge wigs out! Is it possible that there could be something pretty small caught in my pump as to not hamper my "on the water" forward power output but big enough to not want to go through the veins of the bowl or get chewed up by the impeller? Is there a big enough void in between the impellor and the bowl for this to be possible? I have tried everything I can think of for flushing out my pump to get something to come out but all I get is water and no evidence of anything coming out that shouldn't be!! Whatcha guys think, I'm open to any and all constructive ideas on solving this matter before I just pull the jet to inspect the bowl for anything that shouldn't be in there!
 

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Discussion Starter #2
Like I said in the beginning, I apologize for the long drawn out post, but it's late in the evening for me and I wanted to get all the info out there that I though was gonna be important to remedy this problem!! :)
 

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It you can put water in AFTER the pump and it runs cool as you say; yes. there may be a restriction in the little 3/8" hole behind the impeller where the water supply comes from. Remove the impeller and look. Do you have a gate valve or any other type of valve in the water supply line coming from the pump? If you do, these are the two places I'd look first. You'll probably get many ideas here and they may well all have merit, but start here and if you don't find it; we will try to guide you on in a logical process of elimination rather than just hunting down random ideas.

Duane HTP
 

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Discussion Starter #4 (Edited)
Thanks for your reply!! No, I used to run gate valves before the thermostat setup, now it's just a hose that goes from the berk to the front of the motor, which tee's off and goes to the front of the exhaust logs!! I was hoping for a clog in any or all of that so I took it all out and it's all clean as well!! Even took the hose fitting off of the berk and looked through it with a flashlight and all I see is the impeller!

What I'm wondering is if something small could be in there laying at the bottom of the pump when the boats not in the water and is low enough for the driveway flushing to miss but floats up into the middle of the jet when the boat is in the water right around the water level which allows it to get sucked up in the pump water intake path and not out the bowl! I've had the bill to a hat sucked up into the intake of the pump before and had to get the boat out of the water to pull it out because it wedged/sprung itself in the cavity and wasn't about to move anywhere. The crazy thing is that the engine is getting some water because when it heats up, the thermostat does open and allow some cold water in there to cool it off pretty quick! So if there is something in there it's not fully plugging anything up but I'm suspecting it's redirecting some of the flow from going through to feed the motor!! This is one of those times I wish I had or knew of someone with a little inspection camera that I could use to look inside of the pump!! :cool:

Also, no water at all in the oil if that crosses anyones mind!! Please keep pumping out the ideas guys, would love your input especially on the pump theory!!
 

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this may be a bit off course, but since im kinda new i would have thought all the things you have already tried would have remedied the problem. 2 things i can think of

the feed line from the pump has delayered and the inside layer has a weak spot causing it to fold over and causing a restriction.

or

you may have a small head gasket leak that is pumping a small bit of air into the cooling system. this is making steam around the thermo sender and causing it to rise. then when the bubble gets big enough it washes out covering the thermo with fresh water dropping the temp radically.

thats all i got so far. good luck
 

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Discussion Starter #6
Not off course at all!! The delivery hose is in great condition and is only a few years old!! When I took it all out and inspected it all, it was all firm with no soft spots!!
As for your second idea, it could be but find it hard to believe that it happened the same time as the pump plugging up!! The boat never did overheat fully at that time either, never got above 210 but usually it doesn't ever move from 160 either!!

Keep the ideas and input coming, I really wanna get this resolved quickly!! Probably gonna pull the pump bowl tomorrow to check it all out for my own piece of mind, but hoping something else gets brought up before then that I haven't checked yet!!
 

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Have you tried flushing water back thru the pump with the water hose? Also if you're saying you don't have a valve at the pump to be able to shut the wate[HR][/HR]r off you might want to put one on. If you have a water leak after the pump it is a good idea to be able to shut the water off so your boat doesn't sink.
 

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Discussion Starter #8
Have you tried flushing water back thru the pump with the water hose? Also if you're saying you don't have a valve at the pump to be able to shut the wate[HR][/HR]r off you might want to put one on. If you have a water leak after the pump it is a good idea to be able to shut the water off so your boat doesn't sink.
To answer the first response, I have tried flushing out the jet a few ways!! First I've ran water through the pump through the pickup hose and out the back, running and not running! Then I've also taken a big lid from a container I have and with the water running into the jet and the motor running (I've got water running to the motor as well), I've taken that lid to the back of the pump, preventing the water from escaping and making the water build up enough out of the jet to actually drain out the intake. I've let it run that way a bunch of times and holding the cap onto the pump until the pressure builds out and the water just gushes out when I remove the lid!! I've even taken a high powered hose and just hosed out each fin in the bowl, the motor running or not!! I've pretty much tried everything to flush whatever might be in there out, but nothing was ever on the ground after each attempt!!

For your second, that's something I've never thought about doing and will end up putting something inline to prevent that tragedy from becoming a reality ever!! Would suck for sure to have a hose failure like that, thank you for that great idea!!

Keep the ideas coming folks, D day for the pump is coming up tomorrow but would love for a golden idea to pop up to prevent that from occupying my day tomorrow!!
 

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Discussion Starter #9
Well, ended up taking the bowl off last night after all, and low and behold........nothing in there!! So........ looks like I will put it all back together today and slowly go through all the hoses yet again and possibly start looking at the thermostat to confirm that i put it in correctly and hoping it's not the heads!! SUCKS!

Question, when putting this bowl back on, do I need to get get a new gasket and O-ring or can I reuse the gasket with some rtv or such for this install?
 

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Well, ended up taking the bowl off last night after all, and low and behold........nothing in there!! So........ looks like I will put it all back together today and slowly go through all the hoses yet again and possibly start looking at the thermostat to confirm that i put it in correctly and hoping it's not the heads!! SUCKS!

Question, when putting this bowl back on, do I need to get get a new gasket and O-ring or can I reuse the gasket with some rtv or such for this install?
Would always suggest a new gasket for sure unless your is perfect (no silicone) as for the bowl to transom Oring , some use them some dont re the Tstat set up its probably not a bad idea to double check that "install" and also check your water line routing at the 4 port setup , if the lines are wrong (reversed) it will overheat . Incidentally overheating on a jet boat is actually unusual and I suspect relates back to your original issue of debris injestion hats off to your dilligence in trying to track this down systematically Tom
 

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Here is a thought, where do you think all the crap that you sucked up went? I think its time to pull out all the freeze plugs in the engine and flush it out with a water pressure hose in the openings. You will probably be amazed at the build up of sand and crap that is in there
 

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Discussion Starter #12
Well, got the boat back together today and even if the boat still overheats, I'm glad I pulled the bowl because I got to do alot of checking out of the pump and did some much needed cleaning and maintenance!! Gonna take it back out on the river tomorrow just to confirm that it's still overheating, if it is then I will be replacing a few hoses and checking out the motor real well!!
 

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Discussion Starter #13 (Edited)
Well, I took it out today and sure enough the problem is still there!! Not suprised since I didn't find anything in the jet but was still hoping for a small miracle!! lol

So, on the agenda for tomorrow is to do a compression check and go from there since the pump is fine!! I took a video of the gauge to show what I'm seeing when I'm running the boat right now, normally it's pretty stationary on 160 but not now!! In this video, I'm running at a steady 3000rpm with the boat warmed up, and the faster I drive the bigger the temp range is and the faster the movement is! At an idle, the temp will only go from 160 to about 170 and then back again but it takes a while longer for all of that to happen compared to 3k rpm!! It's hard to video a gauge steady enough to not get you sick watching it while you are driving at a fast speed and trying not to hit anyone!! hahaha

 

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Discussion Starter #14
Just posted up the video of the temp gauge, sorry about the delay, I forgot that I had to upload it up to Youtube and post it up that way!! Take a look at it and let me know what you guys think!! The compression test I'm gonna do will probably answer alot or make the mystery even deeper!! lol
 

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Well, did a compression check tonight and low and behold all of the cylinders were pretty much equal to each other!! The biggest difference was 6 between the strongest and weakest cylinders, but gonna get my dad's gauge tomorrow to compare the numbers too!!
 

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Looks like I scared everyone off!! hahahaha

Well, talked with a few other folks today and decided to replace the temp sending unit since it's as old as I've had the gauges in my boat (about 6 years old). Kinda thinking that when I sucked up the stuff in the pump and lost water flow, it would have been the first thing left high and dry without water, maybe the heat got to it and did something to it!! Who knows, at least it's better than messing with the heads and I pick it up tomorrow! Gonna replace my main hose that feeds the motor as well since it feels kinda soft for my liking, and also looking into installing a gate valve like mentioned at the pump in case of future hose failure (great idea!).
 

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Read post #11 again. Your engine is not going to cool if its full of crap!!! I know, flushed about 10 lbs of sand that was caked up from a 460 block one time.
 

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Read post #11 again. Your engine is not going to cool if its full of crap!!! I know, flushed about 10 lbs of sand that was caked up from a 460 block one time.
Hope I didn't offend you with my last comment, it was meant to be a joke more than anything!! If I could walk away from the problem, trust me I would have by now!! lol

And yes, I did read your ideas as well as everyone else so far in this thread and I really do appreciated all of them!! I actually did a prelim flush a couple days ago by taking out the petcocks that drain the block and flushed out the block from the waterpump plate as well as back flushed the petcock holes!! I know it's not the best way to flush it out but I wanted to see just how much stuff would come out and it wasn't much to write home about, hence I forgot to add that event to this thread!! Trust me, it's still on my list of stuff to try, and if this sending unit isn't the problem I will probably be doing that next!!

By the way, did you flush yours out when you got the ton of sand because you were having overheating problems? If not, what made you do it in the first place? Curiosity on my part!
 

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Well, did a compression check tonight and low and behold all of the cylinders were pretty much equal to each other!! The biggest difference was 6 between the strongest and weakest cylinders, but gonna get my dad's gauge tomorrow to compare the numbers too!!
sounds like compression is good. also very even. not to beat a dead horse but perhaps a leak down may find what your searching for. saying that it rises and falls would seem like only a small amount of air entering the system.
 

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By the way, did you flush yours out when you got the ton of sand because you were having overheating problems? If not, what made you do it in the first place? Curiosity on my part![/QUOTE]

It seemed to be running a little warm, but to tell you the truth, it was during tear down to build more HP. When I removed the freeze plugs, what a suprise that was. The water passages were just full of caked on sand build-up. You may want to do a leak down test first. Compression sounds good. No water in the oil or valve covers right? And all plugs look the same?
 
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