MERPerformance
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Thats funny LOL.
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38 Top Gun Cooling Problem
- Thread starter MERPerformance
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Thats funny LOL.
Blue Thunder
New member
What do you think happens with not enough advance? It makes your exhaust gas temps high which could be why your paint is pealing. Like I said, it was just something to consider as a possible contributing factor.
MERPerformance
Sponsor
Not to be a smart a!! timing only changes on cylinders 5&7 and burns paint, we have been talking about the water pick-ups and air entering the system. The engine would probably not even gain rpms under load, I guess since i'am on the dyno I'll try retarding the timing to the point that I burn the paint off the exhaust ports. Since I've been doing this for over 20 yrs I know what the timing is. Thank you for your thought on the problem.
Blue Thunder
New member
5/7 are next to each other in the firing order so they would show the most heat due to retarted timing. Not to be a smart a!! but everything in an engine is interelated. I would have thought in 20 years you might have picked up on this. My bad, carry on with the tunnel vision.........
Geronimo36
Charter Member
To be honest, I haven't had many engines that over time didn't eventually burn the paint off the tops of the exhaust ports... If not totally burned off, definitely browned... Then again, we run up here for hours at a time.. 
I think his main question was the 5 psi fluctuation in water pressure in upper rpms??? I'm guessing it's either from a disturbance in the pick-up (air) or something causing bad water circulation out of the engine. He said he's not bleeding water off the rear of the heads but I'm not sure if the steam pockets can cause fluctions in pressure like that? At least I've never seen it. One things for sure, a few dumps would help facilitate some flow back there and help cool the rear bank of the heads.
I think his main question was the 5 psi fluctuation in water pressure in upper rpms??? I'm guessing it's either from a disturbance in the pick-up (air) or something causing bad water circulation out of the engine. He said he's not bleeding water off the rear of the heads but I'm not sure if the steam pockets can cause fluctions in pressure like that? At least I've never seen it. One things for sure, a few dumps would help facilitate some flow back there and help cool the rear bank of the heads.
MERPerformance
Sponsor
Testing it today, raised the pick-ups to 3/16",to trailing edge below hull. these pick-ups were modified to make adjustments with them, they have a square sleve that slides over the outside with slots and allen head screws holding them. I blended the inner tube and removed the square edge leading into the pick-up. At this point until I test it today I wouldn't add blleed lines to the back of the intake. One change at a time, this has cost me alot of time and money. I have always seen the paint burn away on cast iron ex. ports, if it was just the port burning some paint I wouldn't have concerns, but; I,am talkiing about burning the paint between the ports also. we'll see this morning. Thanks again.
MERPerformance
Sponsor
Blue Thunder, I understand what you are saying and agree with you, I just know for a fact that we have a water issue. The timing is set at 35 degrees, thunder bolt iv with a crane HI-6 Marine box hall effect pick-up which doesn't seem to pickup noises that i have found come from some magnetic triggers. Timing was the same on dyno and checked again in boat, the water temp on my dyno is between 160-170. I have seen Msd distributors retard the timing 10-15 degrees at about 2500-3000 rpms but,they run really bad and sometimes back fire if accellerated to fast. Thanks again
MERPerformance
Sponsor
Tested it today with results! I raised the pick-ups 3/16 below hull took it out, tools, & thermo gun. 1-7 cylinders heads 180-198 degrees not good, removed thermostat same thing. Loaded it up took it back to the shop got some lunch came back to the shop. Went and bought some 1 1/4 clear plastic hose, installed it between the sea strainer and sea pump, put it back in the water got it on plan, no air still hot 1-7 bank 20 # pressure won,t push it. Why is the 1-7 bank getting so hot oil temp increasing engine won't cool down even at 2500-3000 rpms. My part time helper says; lets block the jumper hose between the cross-over and thermostat housing, I told him we need to remove the thermostat also so we don't burn the headers, this is going against everything I do to my builds, I use thermostats and try to use thermostat controlled oil temps. Here's are cooling system parts: Eddie Marine cross-over kits with thermostats, Stainless Marine water pick-ups, Hardin Marine sea-strainers, 3"oil coolers, stock merc sea-waterpumps, changed the -8an fittings on crossover and therm. housing to -10anso more water would cool headers when therm. is closed. We capped the 10 an fittings removed the thermstat bought upon plan 10#press @ 3500 rpm, temps all equal all 4 corners 110 degrees, oil temps down 160 degrees, took the center out of the thermostat installed it,need some restriction! ran it up 20 # at 4500 rpms still cool temps 120 degrees oil 160,ran itup to wot 6000rpms fingers crossed, perfect! Buy the way lowered the waterpick-ups to 1/2 below hull, going to raise them now to 3/16". I don't believe that a -10an hose which is 5/8 I.D. would take that much water awayfrom the block or was the jumper hose putting cool water on top of the thermostat cooling it to the point of not opening it. Looked at an other cross-over set-upfrom Stainless Marine,the jumper doesn't enter over the thermostat, same set-up -10an jumper,what do you do if you want to use the thermostat, listen to Jerry @ Stainless and go to High speed pick-up or maybe try the Stainless Marine thermostat housing off the other boat, guess i'll try that housing,lets see who, is right or wrong on the product they make. This whole deal has cost me pulling the engines and 2 new cylinder heads and porting them, valve job and gaskets plus labor all covered by me,guess I'll find out who's product works. Letyou know soon.My spacekey is giving me aproblem!
Geronimo36
Charter Member
Looks like you solved the temp problem, no???
Maybe you need to run a smaller hose to the crossover. I always thought the hose was smaller than a -10 though, no?
Silly off-the-wall question but was the t-stat installed upside down?
MOBILEMERCMAN
Founding Member / Competitor
Glad to hear progress. On the clear hose in the future, It will tell you more if it is after the motor before the headers.
MERPerformance
Sponsor
It'snot over yet! Removing the thermostat and restricting it along with capping the by-pass isn't the repair, by far is it the way I want it. I know some guys don't like thermostats in the water or for the oil temp, but' I use both when able to. To many suppliers out there build stuff for the marine business and don't test it enough before they sell it or they copy someone elses product and make a change on it and call it theirs. I did some research on what one of the main players in the marine manufacturing does with theirs and what design engineering they put into it.They have been around for a long time and I know for a fact that, their product works and talked to the owner of the company about this problem, I have been having. There is a difference in the design between the two, I am making a change on the housing. I'll let you know how it works and post pics of before and after. This product may work on other smaller H.P. but not on 800 that turn 6200. As you well know this product was purchased because of cost, cheaper! When this is over and I have all the facts I will post it.
Geronimo36
Charter Member
At least you were able to isolate the problem and now it's easier to fix!! 
MERPerformance
Sponsor
Found the cause of the problem! Thermostat housing. Tried to modify it to keep the cold water off the thermostat. The cold water cools the top of the thermostat sending a false temp on the water temp, making the water in the heads and block rise in temp and not cool down and develope a steam pocket on cylinders 1-7 also causing the oil temp to rise beyond to point of wanting to cool down, so hot the oil was tring to cool the cylinder head. This was a system from Eddie Marine' cross-over with by-pass to thermostat housing and a 140 degree thermostat. Here's what finally worked took a housing made by Stainless Marine, cast stainless. These are made with a diverter cast into the housing that keeps the hot water over the thermostat and the cold water away from it by directing it to the exhaust, we changed it to have 2 # 12 water outlets and a #10 or #12 by-pass fitting both off these worked on the other 2 boats, one was a 33' Fountain 1987 with 800s, #4 drives, original water pick-ups, the other boat 2004 38 top gun with 815s XR drives sportmaster lowers with modified water inlets, Marine Machine strainers with air dump check valves going over board. Both equipped with Stainless Marine housings and thermostats 142 degrees. Taked with Mike @ Hardin Marine today about their kits, this problem seens to exist on higher hp set ups using this style housing, the have a housing that is spring loaded to 10# allowing the water to mix and dump out the exhaust. I'am ordering 2 housings tomorrow from Jerry, Tried of being a test subject for non proven products. So if you have encountered this problem in the past with thermostats and cross over kits maybe this will help. I 'am sure this product works for stock power applications but, not higher HP set-ups.
2112
Founding Member / Contributor
How did you modify the sportmaster pick ups and do you have a picture of the air dump/check valve attachment point on your strainers?
What raw water pressure are you looking to get?
Much appreciated :USA:
txriverrat2001
Charter Member
Good info!! I have a client with a 38 Fountain - not real big power - but the same scenario. One bank gets way much hotter when the T-stats are in the housings (generic aftermarket with crossovers) and the bypass does dump directly on top of the T-Stat - I agree with you on running T-stats - control is always much better!
Keep us updated and thanks for sharing.
2112
Founding Member / Contributor
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