Overheating 1995 88 SPL

[Caseyuconn]

Finally got my boat in the water today after doing so much work to the motor.
I changed the outer exhaust gaskets, the thermostats and the water pump.

The motor was pumping good out of the telltale, very strong. I took a 20 min ride up river at low RPM and as soon as I reached the Sound the alarm started going off, constant noise, and the tell tale looked like it was steaming.

I got it home and ran it on the muffs. One thing I notice is the telltale stays ice cold even after 15mins on the muff.

My Questions are:
1. If the tell tale is pumping strong the water pump must be working correctly, right?
2. If I just replaced the thermostats and water pump what else would make this thing overheat?

Thanks

 

[Daviet]

Re: Overheating 1995 88 SPL

When running an engine on a hose the water pressure will overcome a defective pump. The tell-tale is the first thing that gets pressure from the pump, it does not mean the cooling system is in good shape, just that the pump is working. If you are not getting a tell-tale while running in the water or in a barrel, remove the lower unit and recheck the pump. Sometimes the tell-tale will get plugged up, but since your heat alarm went off, I would look at the pump.

 

[Caseyuconn]

Re: Overheating 1995 88 SPL

The telltale was strong the whole way in the ocean. It almost seems like a thermostat not opening issue, but they are brand new 143 degree OMC thermostats...And I rebuilt the whole water pump..

 

[emdsapmgr]

Re: Overheating 1995 88 SPL

Daviet is right on with his comments. The issue is, can the water circulate through the rest of the engine, then out the exhaust. If you still have an overheat (even with new stats,) the the water may not be circulating through the powerhead. You could have one of two issues. 1 you could have one or more of rubber water deflectors out of postion by each cylinder, even a restriction by those deflectors. 2. You could have a restriction elsewhere in the powerhead, such as in the cylinder head covers. If you have access to a laser temp gun, check to see if one or both heads are overheating. That will tell you something.

 

[DJ]

Re: Overheating 1995 88 SPL

My vote goes for the deflectors and a potentially defective stat..

 

[emoney]

Re: Overheating 1995 88 SPL

If you need to buy one of those IR temp lasers, Harbor Freight has them on sale (with a coupon) right now for $29.98. I only know this because I just payed $39.98 two weeks ago:facepalm:

 

[Caseyuconn]

Re: Overheating 1995 88 SPL

I am not familiar with the deflectors, anyone care to elaborate?

 

[DJ]

Re: Overheating 1995 88 SPL

I am not familiar with the deflectors, anyone care to elaborate?

They are basically small pieces of rubber tubing, in the cooling passages, under the heads. In the block. They can deteriorate and move around.

 

[Daviet]

Re: Overheating 1995 88 SPL

#10 in the breakdown below. They make the water circulate in a specfic direction.
http://www.ishopmarine.com/ishop/js...CatFilter=BRP&eCatSupFldr=supplier-100-005-EJ

 

[Caseyuconn]

Re: Overheating 1995 88 SPL

I appreciate the assistance.

It confuses me that these would be the culprit. I just purchased this boat/motor and it ran fine during the test run.

Replacing these includes the removal of the cylinder head cover not the cylinder head correct? This sounds like a recipe for broken bolts to me.

I had asked this earlier but just want to verify. If the telltale is strong at idle in the river is this indicative of a properly functioning water pump?

 

[Daviet]

Re: Overheating 1995 88 SPL

How long was the test run? You have to remove the cylinder heads to replace the deflectors. Correct, the tell-tale is an indicator of the condition of the pump, you could have problems upstream of the tell-tale that could cause overheating problems.

 

[DJ]

Re: Overheating 1995 88 SPL

One good overheat and then a nice strong pump can displace the deflectors.

You can get the heads off without removing the head covers. Although, the covers are easy, especially on the workbench.

 

[emdsapmgr]

Re: Overheating 1995 88 SPL

The rubber water diverters direct water flow around the cylinders in the block. Not only can these diverters get out of place, but they can accumulate debris by them, restricting the water flow through the block. Here is a picture where the right water diverter has moved out of position. The left one is correctly positioned.

 

[emoney]

Re: Overheating 1995 88 SPL

And, the strong tell-tale stream, doesn't mean that the water diverters aren't malfunctioning. The tell-tale just let's you know that water is pumping; not if it's going to the right places in order to cool the block.

I'd still, however, double check the t-stats. Just because someone sold you a new part doesn't mean it's a functioning part. If they cook right, I'd believe these guys about the diverters and take a look (as much of a hassle as it sounds, it's better than an overheat).

 

[Caseyuconn]

Re: Overheating 1995 88 SPL

Anyone know of a good way to test the diverters without disassembling the heads?
If I remove the hose on the lower end of the cylinders would this tell if water is making it through the head properly?

I would like to diagnosis this without ripping apart the heads and thermostat covers.

Thanks

 

[emdsapmgr]

Re: Overheating 1995 88 SPL

You have to pull the heads to inspect the diverters. That means new head gaskets. Check your head temps with a laser temp gun. If you know only one head is overheating, you can just pull that head off.

 

[Faztbullet]

Re: Overheating 1995 88 SPL

If you have the t-stats installed reversed it will cause this and it can be done.

 

[Caseyuconn]

Re: Overheating 1995 88 SPL

I have been thinking about the T-stats and how I put them in. It would be difficult to put them in backwards considering I have the manual however it is not impossible.

I may pull the cover to take a peak tonight after taking some temperature readings running on the muffs. I do notice that the telltale is ice cold all the time, however as someone pointed out I think this water exits before entering the heads. Also I have run it for over 15 mins on the muffs with no overheat.

 

[Caseyuconn]

Re: Overheating 1995 88 SPL

I bought an infrared thermometer today and ran the motor for 20 mins on the muffs.
Here are the results after 20 mins of idle

+Thermostat cover was 137
+Port Head midsection just inside the over seam was 153-157 F (Head cover was steady 146)
+Starboard head midsection was 155 - 163 F

The starboard head would go up to 163 then immediately down to 155

I believe my T-stats are 143 F. Are the numbers above average or acceptable??

Thanks

 

[emdsapmgr]

Re: Overheating 1995 88 SPL

You will get an overheat horn at 212, which will silence when the head temps get back down to 175. 163 is above normal and should be investigated. Your temps are still high, for idling. I'd be looking for normal temps just over 143 when idling on the hose with cool household water. In the summer, temps can get up to 155. The 155 would be in the dead of summer, when idling in warm lake water for a while. Measured on each head.