150 black max overheating

The motor runs awsome but when Im traveling between 15mph and 25mph she overheats but if I slow down to 10mph or speed up over 30mph she cools right down. Any ideas would be greatly apreciated.

Jeff Z

Re: 150 black max overheating

No responce? Water is coming out of the pisser,Pulled out the t-stats and put them in boiling water and they both open up. Pulled the heads off,cooling passages look fantastic as do the cylinders and pistons. Im stumped. Im still gona replace the impeller just because I dont know when the last time it was changed.

Re: 150 black max overheating

Don't just change the impeller, get a water pump kit and do it right.

Re: 150 black max overheating

Thats the plan,Im ordering pump kit, and new t-stats.

Re: 150 black max overheating

You don,t mention anything about the boat hull, at 15 to 25 mph the hull might be pushing water and making the engine work harder. A weak waterpump will allow it to overheat. When you are up to speed the water pressure feeding the water pump increases and helps the weak pump. At slow speed the weak pump provides enough water as the engine is not working hard. Rebuilding the pump will likely cure your problem, the thermostats are a good idea but likely have nothing to do with what is happening.

Re: 150 black max overheating

Thanks,Ive ben racking My brain and over analizing this (lol) and thats kinda what I was thinking also. Its an 86 capri bow rider with a not so deep hull.The pump rebuild kit should be here thursday.It didnt include the housing tho. Is that ok?

Re: 150 black max overheating

Water pressure is the most important diagnostic tool here. The poppet may be failing, or you may not have sufficient water, ie impeller end leaks past bad wear plate or housing.

Overload will heat em up, also. If it's over-propped and you're pushing hard, it'll overheat. Prop it so it can see near 6000 rpm with a light load, and it should be OK for all loads.

hope it helps
John

Re: 150 black max overheating

Thanks John,She might be over propped since she never gets above 5500 rpm.Im thinking maby $2000 for this boat wasnt as such a good deal as I thought.lol

Re: 150 black max overheating

What you're dealing with is normal maintenance. If you hit some crap weeds and manage to suck them into the motor, you have to fix it. 5500 WOT is technically the right prop for it. If it doesn't have a water pressure gauge, get the kit (under $50) and put it in. Then you have both early warning for failure, and the most useful diagnostic tool you could have.

Re: 150 black max overheating

I had a few pieces of gravel (oyster) on the inlet side of the poppet do that to me as well. It seems to have made the poppet open later than it should have. Ran fine at idle, and at WOT, after the pressure was enough to open it. As a matter of fact, gotta go do it again this morning. It ran PERFECT for a month, then drug a reef a couple times and it started again. One of my symptoms that it is the poppet is that its not coughing water out of the exhaust, only steam. Right now, mines not alarming again yet, but it's steaming again. The pisser gets its water from the thermostats, the other small amount of water the comes out the back (not thru the prop) comes from a different place. You can have one partially clogged and it still pee strong and overheat. I changed my water pump, housing, both tstats, and cleaned my poppet, all at the same time and wow what a difference!

Re: 150 black max overheating

So,um,there's suposed to be water coming out of the exhaust? Not mine aparentily.lol
You might be on to something there.where's this poppit you speak of?

Re: 150 black max overheating

you are going to have to pull the powerhead to get to your real problem, at the adapter plate below powerhead. It will be filled up with crap!