'88 150hp - 18 month prob - o'heating

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,780
Re: '88 150hp - 18 month prob - o'heating

Well Fine. <br /><br />Thanks to my belligerance we are getting a good discussion going here that hopefully will help someone make the right decisions. Seems we have several knowledgeable people on the same sheet of music which speaks of truth and facts. Great!<br /><br />Back to my pedigree; all this temp stuff is new to me as I have been away from boats for 10 years and we (Merc) didn't have all that stuff on my '89 tower.<br /><br />I will take a look at your schematic (after I finish surfing the site) as I am genuinely interested. So interested in fact that I spent all of 2 hours today looking thru my maint manual for some mention of "don'ts" i.e. don't remove this or that.....found nothing.<br /><br />He's still not out of the woods. He said he is running 20 at 3100 with a 19 pitch prop on a 150 on a 17' boat with a gear ration of 1.87 (according to the sales brochure).<br /><br />Now I agree that lugging, like he said his wot is 5000 and the sales broc says 5 to 5800, so he is really lugging it, and lugging adds to overheating....will give you that. Butttttt the numbers don't add up.....just a sec going to the prop calculator. The numbers:<br /><br />Gear 1.87<br />Pitch 19<br />Theoretical speed <br /><br />3100rpm - 30mph, 5000 48, 5800 56.<br />Assuming slip of 33% (based upon his numbers) at 3100, 20 (estimated) at 5000 and 10 (est) at 5800,<br /><br />Actual speed: 20 (his numbers) 38 calculated, and 50 calc.<br /><br />I believe these numbers and based upon that I don't think he is overloading a 17' boat with a 150 with a 19" prop.<br /><br />Something doesn't make sense.<br /><br />One final thing and I'll leave.....the maint manual did say for overheating, be sure and insure that your water pickup holes (on your skeg) are all under water. We didn't verify that.<br /><br />Mark
 

KCLOST

Commander
Joined
Jun 22, 2002
Messages
2,095
Re: '88 150hp - 18 month prob - o'heating

Texas, <br />This lugging problem could very well be it!<br />I didn't mean to suggest that it wasn't, I just wanted to make sure the poppet valve wasn't removed...<br />I guess we should have asked him if he had the same symptoms without pulling skiers...<br />And also as Andy suggests, decarb the darn thing first to ensure that isn't a cause.... Retest with the engine running at the recommended rpm at WOT...<br />However, I still want to know what his exact WOT rpms are, and if that poppet is operating properly...
 

ronnieboy

Petty Officer 2nd Class
Joined
Feb 5, 2006
Messages
149
Re: '88 150hp - 18 month prob - o'heating

hi guys, my ranger 374 is 18 feet,and very heavy, i use a 4 blade stainless turbo prop of 19 pitch and my 150 mag ll turns 5800 wot with motor tilted to raise the bow, dead stop to full plane in 30 feet, boat will do this loaded or unloaded, dont think his is over loaded, check the small stuff, one thing at a time, to eliminate problem, good luck ron
 

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: '88 150hp - 18 month prob - o'heating

ronnieboy-<br />You are right 5800 RPMs @ WOT is not lugging an engine, but he said he is only getting 5000 RPMs at WOT and that is lugging an engine.
 

mortey

Cadet
Joined
Mar 21, 2006
Messages
10
Re: '88 150hp - 18 month prob - o'heating

Hi Guys, thanks for all this info, just to clarify one thing though, I mentioned that the WOT is somewhere over 5000rpm as it does rev quite freely, I havent actually taken an exact note of what it is, will do next run though. My boat (Haines Hunter 17ft) is a relativley light boat too. My gut tells me it is not lugging that is the cause (may add slightly maybe?) but not the main cause. I will run with fitting a new poppet, new thermo's, rechecking all channels (still have heads off) put it all back together and see how we go.<br />Safe boating
 

KCLOST

Commander
Joined
Jun 22, 2002
Messages
2,095
Re: '88 150hp - 18 month prob - o'heating

ronnieboy,<br /><br />I have about the same boat set-up as you... Ranger 371 V with a Merc. 175 Black Max...<br /><br />I find your prop pitch pretty interesting! I know I have an extra 25 horsepower to play with, but I'm running a Lazer II 25p 3-blade prop and can get up on plane very quickly as well. WOT rpm is 5800 with the motor tilted out! I also have a 24p Trophy 4-blade and have an even quicker hole shot but loose a few mph at WOT.<br />63mph top end speed with the Lazer.<br /><br />I'm thinking of trying out a 25p trophy and see what happens...
 

mortey

Cadet
Joined
Mar 21, 2006
Messages
10
Re: '88 150hp - 18 month prob - o'heating

Hi guys,<br /><br />Sorry for the delay! Well i finally got time to work on the merc. I ended up pulling the whole thing down again and I had a retired Service Mananger for Merc of some 30 years or something come around and have a look...nothing irregular found. So replace poppet valve spring and all gaskets with everything looking good. I also fitted a temp gauge with numeric readings on it.....<br /><br />Now the test drive.......I found that the buzzer does not come on now unless i am running WOT for about 1min or more. WOT is about 5200rpm. The temp gauge when on my cruise speed of about 23 to 25knots is about 190 to 200F. And when WOT it goes to 230 to 240F. So it is better and I put that to the new spring though there still seems to be some mongrel gremlin in there that NO one can find! Though as I mainly only opertate at the most at 28knots and the buzzer is not going off at this i suppose i will just keep driving it until sometthing happens then get a new one!<br /><br />So thanks again for all your info and if you end up coming up with anything else let me know.<br /><br />Cheers
 

ronnieboy

Petty Officer 2nd Class
Joined
Feb 5, 2006
Messages
149
Re: '88 150hp - 18 month prob - o'heating

mortney, i still say you have to check for proper seating pressure on poppet spring assembly. you should feel it loadup when you assemble and install bolts, this will help midrange, topend will depend on thermostats being open, test by removing stats for ONE wot run just to see if it cools. if not pluged up somewhere, this should let the motor run cooler. have to check the small stuff, thats usually what it is. kclost sounds like we have very similar boats, would like to have a 175 but my 150 sucks toooo much gas as it is. nice to hear it run across the lake though, lots of lookers , hahahahah ron
 

ronnieboy

Petty Officer 2nd Class
Joined
Feb 5, 2006
Messages
149
Re: '88 150hp - 18 month prob - o'heating

forgot to proof read, be sure to check and replace rubber seals on TOP and bottom of water tube . if top is leaking , will let exaust into water jackets, wont cool with air in it. if nothing else, seal top seal with blue silicone for temp check, will eliminate some of the possibilities, good luck ron
 

mortey

Cadet
Joined
Mar 21, 2006
Messages
10
Re: '88 150hp - 18 month prob - o'heating

hi Ron,<br /><br />I can feel the poppet load up when I install it. I have tried running without thermostats and still overheats. Have replaced both seals.<br /><br />Thanks
 

ronnieboy

Petty Officer 2nd Class
Joined
Feb 5, 2006
Messages
149
Re: '88 150hp - 18 month prob - o'heating

might be getting exaust gas inside waterjacket cover, not difficult to replace , just take off covers expose plate with coils on it, and remove carefully with wrench, inspect both sealing surfaces before cleaning to see if a leak can be detected, i made my gaskets by using sheet material from auto parts place, not hard to do. seal with non hardening sealant and hand tighten 2 times, one cold one hot. if this dont help , i bet you have a passage stopped up. have to compress air it out. are you SURE the top seal is good on water tube? silicone to be sure, hope this helps ron
 

rocks

Seaman
Joined
Aug 19, 2004
Messages
64
Re: '88 150hp - 18 month prob - o'heating

Mortey, Had your same problem for 2 yrs.At 3000 rpm alarm,but good tell tale.Finally took to a good mech.. Turns out I was sold a impeller for a mercruiser I/O. Now pressure build to 25 psi at 3000 then drops to 15-20 at cruise.And the tell tale acts completly different,I always thought a really strong pee was good.I was wrong.
 

mortey

Cadet
Joined
Mar 21, 2006
Messages
10
Re: '88 150hp - 18 month prob - o'heating

have had the water jacket cover off, all inspected - water ports etc, all ok. Have checked all passages for blockages.<br />I will silicone the water pipe next time it is out.<br /><br />Thanks again
 
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