Mercruiser 150

[CaptRon66]

Oh boy. Looking over the used engine I bought and now see a big mistake I made. At least it came with exhaust which has never seen h20 .Owner sold it as a 250 ci engine. I noticed it had flat top pistons today. It's a Chevy 230. Not a 250. I'll have to double check the stroke. My boat was built in 71 and it's solid. Pretty heavy 23 footer. How can I tell what a difference in top end and out of the hole performance it will make dropping this in with 15 hp less than a Mercruiser165? It's not exactly a speed demon now and I'm not crazy about less hp. Maybe drop a prop size with same outdrive?

 

[180shabah]

Re: Mercruiser 150

That is alot of boat for a six. The only way to know for sure, is to run it. What was WOT with current prop and 165hp?

 

[cr2k]

Re: Mercruiser 150

Time to pony up for premium and bump the timing a few degrees.

 

[Bondo]

Re: Mercruiser 150

Ayuh,... Does this block have the motor mount boss on the front corner..??

 

[mkast]

Re: Mercruiser 150

Time to pony up for premium and bump the timing a few degrees.

Rookie mistake.

 

[CaptRon66]

Re: Mercruiser 150

The old engine, Mercruiser 165 previously ran 4100 rpm wot with a prop of 15.25 x 15.
Yes,The engine has all the motor mount holes needed for marine including the extra ear. It even came with rear bell housing and front stand.

 

[HT32BSX115]

Re: Mercruiser 150

I had one of those 230 cu-in 150hp mercs in an 18' Mark Twain.

Dad bought it new in 1966 and I sold it in 2005....It never had the head off. Not a lot of complaints. The hr meter died in the early to mid 80's at about 1500-1800 hours.

It ran fine in the 18' boat. Might be a little anemic in a 23ft boat though. If I had kept the boat I would have gotten a 250cu-in 6 and built it up a little.



Cheers,


Rick

 

[CaptRon66]

Re: Mercruiser 150

I finally got the engine started on the garage floor. Used an old distributor to spin the oil pump before hand. Oil pressure was good with mech gauge. After running the engine did a compression test. Cylinders 1-4 were between 150 and 154. 5=160 , 6=180. Why would cyl 6 be so high?

 

[CaptRon66]

Re: Mercruiser 150

I should have added prior that this engine was allegedly rebuilt and then sat for years in a shed. I don't see carbon build up on top of the piston when peaking through the plug hole with a maglight.

 

[mkast]

Re: Mercruiser 150

Why would cyl 6 be so high?

Because it's in better shape than the rest?
Do a cylinder leak down test on the engine.

 

[CaptRon66]

Re: Mercruiser 150

The 180 psi is higher than spec and I wasn't sure if a flat exhaust cam lobe could cause a high compression test result.

 

[CaptRon66]

Re: Mercruiser 150

Discovered what caused the high compression in the 6th cylinder. The exhaust manifold which was supposed to be never used was cracked and leaking into the exhaust. The manifold had no rust inside while inspecting with the end plates off. The previous owner must have let a new manifold freeze. Engine block pressure tested good again. Somehow I missed this when running the engine on the floor. Maybe because the manifold didn't sit with water in it for long. After running in boat on hose it was obvious. Water spray out the spark plug hole #6 during compression test( after engine shut down for 10 min). Replaced manifold,all dry and compression between 152 and 158 psi in all cylinders. Real test comes within the next few days after the boat is launched.

 

[zbnutcase]

Re: Mercruiser 150

Yes a cam going flat can cause a high compression reading.