1978 Evinrude 35853R 35HP - Exhaust housing cover causing problems

[NicoPags]

down to the very last problem.
Paid mechanic to do a full power head rebuild. He did a good job and the motor runs like a whip finally. At years end he had me come collect the boat as he winterizes and stores boats during the winter. He too is well aware of this problem we are having however said we can tackle it in spring. So, when the housing cover is attached to the housing, the tale stops spitting the o/b starts to heat. However, when the housing gasket is not connected it runs amazing (I witnessed myself). the symptom points to an exhaust issue. It was originally thought that the exhaust tube in the housing may have been pinched off during the power head install. After he removed the power head and carefully reinstalled it, the same symptoms repeated. He did mention, ugh, a hairline crack in the ph. Any thoughts or suggestions?
Here is what's brand new
Pistons, seals/gaskets, thermostat, water pump, prop(worth mentioning as its a prop exhaust?),starter, electrical. This motor was rebuilt top to middle.

 

[jimmbo]

"a hairline crack in the ph" what exactly is a 'ph'?

Ok It sounds like you are saying the engine runs poorly with the cover on, but runs fine when it is off. If so you might very well have exhaust getting in the cowl. There are a few ways it can. The gasket between the powerhead and the midsection, the Exhaust cover and the block. You claim the powerhead was removed,and the exhaust tube was examined, inspected, then put back together. Was a new gasket used?

 

[F_R]

My money is on a sealing problem with the water pump. Exhaust pressure is blowing gasses into the pump, killing the prime. Remove that inspection cover, exhaust pressure is relieved, and pump works again.

Just my guess. Let us know what you find out.

 

[NicoPags]

Thanks for the replies. Jimmbo what I meant was a crack someone on the body of the power head unit. And yes a second new gasket was put on the second time. I personally didn't find it likely. Based on f_r suggestion I will first look at the water pump seal. The mechanic did say that every gasket was changed from the water pump and up.

 

[oldboat1]

Might look for small holes on the leg, particularly up toward the top under the powerhead -- more to the point, look for small plugged holes (open them up). In addition, think I might be tempted to pull the l.u. and look for any kind of blockage anywhere up in the leg. (Think mouse or wasp nests.) Low tech stuff -- flashlight and maybe a wire coat hanger. Also probe outlets on the rear of the leg up under the powerhead.

 

[F_R]

Is the spacer tube in place, above the water pump?

 

[NicoPags]

I'm going to drop the lower unit tonight and inspect water pump F_R, along with Oldboats suggestion. This damn 9-5 gets in the way

 

[NicoPags]

Fixed. New water pump and orings on the spacer tube