Cleaning out the Cooling System

[4x15mph]

I am having problems with my SB engine overheating on my last trip out and I think it is due to sand clogging up the cooling system. Apparently there are some cooling veins (3?) that need to be looked and and possibly unclogged but I don't know how to get to them.

I started taking off the exhaust ring but I am not sure what to do next. I have the service manual but it isnt clear to me through reading that either.

Has anyone done this before and can they provide some advice? Thank you

 

[Speedling]

Well, to be honest you need to pull the engine assembly out. You can ty to do it without, but it's actually harder.
Then, you will see all the bolts etc under the exhaust as well. It will be much easier to fit the exhaust over that sleeve again when putting it all back together.
As far as where you may have cooling issues, once it is all apart you will be able to run the hose over everything very easily.

Again, pull the motor. Those engines are easy to work on, but only on the bench. While you're at it, do a top end rebuild if you haven't recently. Maybe even bore the cylinders and get oversizes pistons and maybe even mill the head for a bit more compression. I would highly recommend all yamaha oem gaskets as the aftermarket ones i have seen are not up to par.
If you do any of that fancy go fast stuff, let me know with a tag, but the top end rebuild is supposes to be done every few seasons

 

[Speedling]

https://www.shopsbt.com/pdfs/y11001200npv.pdf
This may help as well

 

[4x15mph]

@Speedling , this was very helpful. My compression test suggests that the engine is strong so I am holding off on any rebuild. I have learned to leave well enough alone since once I start something, I make it a larger project.

Do you have other ideas on checking the condition of the cooling system? I ran it on the hose yesterday and I was getting what looked to be the same flow out of both exhaust outlets. I also have water out both pee holes when on the water.

I will add that yesterday, when I was trying to look at the ring assembly, I pulled off the exhaust water outlet/hose and blew air through it with my mouth. At first air wouldn't pass through but after a few seconds it seemed to "pop". I was then able to blow through that tube like a straw. This may have just been water in the line that I had to clear first but I was wondering if that could have been the clog.

Again, if I can see water circulate on the hose, that would tell me that it isn't clogged. Right?

 

[Speedling]

Right, but you could also use weed whacker line through all the hoses and lines to be sure they are clear

 

[Cobra Jet Steering LLC]

The heat sensors on those engines Especially the exhaust sensors are notorious for going bad, I even had a bad sensor on my 2010 s h o.
Usually if the sensor goes bad it will continue to give false readings of the engine overheating.
On the other hand sand or weeds can block the pump screen and temporarily restrict the flow of cooling water to the engine and make it run hot. I would use a non contact thermometer to get readings from the two engines when they are being used just to see if in fact one is running hotter than the other.

 

[4x15mph]

@Cobra Jet Steering LLC , that is a great idea. Do you mean a thermo similar to what I can get from Harbor Freight? Where would i take the reading? Point it at the exhaust or on the top of the engine manifold? I haven't used one of these before

@Speedling , i will spend more time today using weed whacker line through the hoses. It doesn't seem like I have a clog though since water circulates but it could be a small restriction somewhere.

I am going to run a quick compression test today (again) so that i don't overlook something more critical with the internals.

 

[Speedling]

Good ideas about checking the temperature.
Maybe that's how i came about my infrared thermometer. ..

 

[4x15mph]

Compression is great across all cylinders and matches the port side. It is never a wasted effort to perform this test as part of troubleshooting.

Hmmm... next will be the infrared temp check when I get it out on the water.

 

[Cobra Jet Steering LLC]

If you take readings from the block the exhaust manifold and the water box on both engines and they are close on both you probably have a defective sensor, finding the culprit is the hard part but it is usually the one on the exhaust system. If you check with green hulk I am sure people there have plenty of posts about the 2 stroke sensors and where they are located etc.\

The non contact thermometer you get at harbor freight is all you need , I also use those to monitor the wheel bearing temps on my trailers, If one gets hotter that the others it usually means a bearing is going bad however I would imagine that won't work for wheels with brakes . You can also take that to the beach and point it at the girls to see witch one is the hottest.

 

[4x15mph]

I originally described my problem as overheating but I think that was more the result versus the real problem. In other words, the starboard engine is actually bogging down and eventually losing RPM's to the point where it would seem like it is overheating (RPM <3500) or it is overheating as a result of whatever is causing the bogging (i.e. running lean and causing it to get hot).

I brought it to a dealer and they blew out the SB cooling system. I was told they "thought" they cleared a jam but I have to say that I was not surprised when I brought it to the lake and continue to have the same problem.

Here are some important points for those that can think through this and help me attack this systemically. I really appreciate it!

1) SB engine problem only
2) Even compression across both engines and all cylinders
3) I have a groupk fuel pump that is a single fuel line out and then splits fuel to both engines. This is after the fuel filters (sierra fuel/water filters) so I think any fuel problem would affect both engines
4) I get water through the pee holes when on the water and I get water out the exhaust and pee holes (WOT) when running on the hose
5) I recently had a problem with an impeller wear ring (replaceable type) so while replacing that, I had the jet pumps rebuilt, new impeller ducts, new impellers, and new wear rings. The back pumps are all new and the boat was working great before the impeller ring was torn up and I completed the "fixes".
6) I replaced the plugs a couple of weeks ago. They all look decent to me and they look similar across both engines. I think one of the easier tests will be to switch spark plugs between engines and while I did that last night, I have not tested it.
7) The engine runs fine when out of the water and on the hose. I am sure this is because I don't run it for the length of time and it is a lot different being in the water.
8) the cooling system was flushed out by a local dealer. They did not look at the exhaust ring and clear out any holes internal to the exhaust. Given that water is flowing on the water and the hose, I am not sure that would be a likely problem.

I have read hundreds of posts on the forum trying to figure out next steps. I am sure one of the next best steps would be to clean/rebuild the carbs since I know that I have not done this over this year or last. I don't have any records of when the previous owner did this either.

How would you go about troubleshooting this next?

Thank you

 

[Cobra Jet Steering LLC]

I have heard of the water boxes getting clogged and even internal baffles coming loose to obstruct the exhaust.
first you need to take some random temperature readings and be sure it is not overheating .
You need to see if the carbs are all connected, I found one once where the linkage had come apart and the rear carb was not opening with the others.

 

[4x15mph]

Linkage seems okay from the outside. I think I am going to swap the carbs as a next step and see if the problem follows the carb. If it does, I will clean and rebuild each of the carbs. Sound right?

The temperatures that I have taken recently do not suggest overheating but I am sure if I let it continue to bog it would get to the overheat point.

 

[Cobra Jet Steering LLC]

check the linkage between each carb and be sure the carbs are all opening properly and evenly

 

[4x15mph]

Carb rack is off and the choke and throttle valves all look to be opening evenly. Next, I am going to break down the carb and look at the fuel filters inside each carb

 

[Scottintexas]

I agree with Jeff about the random temp readings and try to isolate when and where the issue is.

I have no idea about 2 strokes but just a thought,

We had a member at YJB that had intermittent over heating and it finally turned out to be the "veins" inside his exhaust manifold. They had become encrusted with sediment and would let enough water through to work the pee hole but eventually over heat.

look at page 2 of this post near the bottom for pictures,
http://yamahajetboaters.com/forum/viewtopic.php?f=1&t=40908&start=15

 

[Seadeals]

Though it is probably no consolation, I think you have done a very good job working through the logic on this one. A carb swap definitely sounds like a good next step after you check temps as it would isolate or eliminate a lot of intricate parts from the equation. Improper fuel/air ratios cause bogging, even if only in one cylinder. A lean ratio can explain atypical heat and will eventually lead to compression problems, so don't run her too hard until you know they are good. I am glad compressions continue to check good. Keep us posted.

 

[4x15mph]

I changed the approach since there were plenty of gaskets and I pulled off fuel lines in order to remove the rack. I thought it was a good idea to rebuild the carb while I had it out anyway so my first step will be a rebuild and retry. If that doesn't fix it, I will swap carbs.

 

[Cobra Jet Steering LLC]

On those carbs usually all you need is to clean the filters and replace the diaphragms those are available separately. I learned to leave the pop off pressure alone and to restrict the return line after the carbs.
People usually place an old carb main jet in the line or something similar to get some back pressure, the fuel pump on the front carb may also be an issue or the pulse tube if it is loose or leaking.

 

[4x15mph]

Thanks @Cobra Jet Steering LLC, @Scottintexas , and @Seadeals . I have new gaskets and carb rebuild kits on their way. Why not rebuild the carbs? When I tore these apart they looked fugly and not how I would want to take care of things. Hopefully this helps the problem but if it doesn't, it needed to be done.

SBT is awesome! I talked to them yesterday and @Cobra Jet Steering LLC , they told me to use the same spring and control arm along with the new rebuild kit. They are sending me all new gaskets and I can't get over how much their service/sales people know as far as instructing me what to do. #SBTyouRock

Parts will be here on Saturday and I will continue with this. Thanks for all of the help.