88 Merc XR4 150 Troubles

Nachman

Cadet
Joined
Jun 4, 2010
Messages
10
First Thanks for your help! I have been lurking and learning the ins and outs of my "new" 150 BMax thru this forum and all of you in cyberspace have great insight and words of wisdom for us all.
My issue is a hard starting, rough idle, smoky XR4 that when she's running is a power beast. She'll run and start pretty well when she's hot, but will be hard to start when I'm ready to move to a different spot on the lake. She will respond from a few push chokes but won't idle or roar to start unless I give her some extra throttle. Sometimes she dies when I move back to idle, and the whole process repeats. I can install ears in the driveway, choke a few times, crank, choke, crank, give a little throttle and she comes to life. Move to idle and die. Try again and she starts right away. Will run at idle, (a bit rough) for as long as I need (3-5 min). Turn off and she's hard to start.
I am new to HPERF outboards as my last one was a Nissan 70HP that was a jewel.
What can i do to get her to respond to my needs? She sounds floody at times and I wondered with the smoke if she is mixing oil at a bad ratio or just needs a good cleaning. Previous owner was meticulous with care and used the right additives for ethanol and such, commented that she was hard to start sometimes......All you input is greatly appreciated.
Dave
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: 88 Merc XR4 150 Troubles

First Thanks for your help! I have been lurking and learning the ins and outs of my "new" 150 BMax thru this forum and all of you in cyberspace have great insight and words of wisdom for us all.
My issue is a hard starting, rough idle, smoky XR4 that when she's running is a power beast. She'll run and start pretty well when she's hot, but will be hard to start when I'm ready to move to a different spot on the lake. She will respond from a few push chokes but won't idle or roar to start unless I give her some extra throttle. Sometimes she dies when I move back to idle, and the whole process repeats. I can install ears in the driveway, choke a few times, crank, choke, crank, give a little throttle and she comes to life. Move to idle and die. Try again and she starts right away. Will run at idle, (a bit rough) for as long as I need (3-5 min). Turn off and she's hard to start.
I am new to HPERF outboards as my last one was a Nissan 70HP that was a jewel.
What can i do to get her to respond to my needs? She sounds floody at times and I wondered with the smoke if she is mixing oil at a bad ratio or just needs a good cleaning. Previous owner was meticulous with care and used the right additives for ethanol and such, commented that she was hard to start sometimes......All you input is greatly appreciated.
Dave

quick check -- a couple of minutes after shut down, crack the fill cap on the boat oil reservoir. It should be flat. If it's pressurized, replace the check valve that supplies pressure to it. (starboard side, low forward.)

First things first.
General health.

What is the cranking speed compression on each cylinder?
What is the idle speed, on the water in gear.
Does the idle stabilizer work right, or is it disconnected? (Tests in the maintenenace manual.)

Then basics
Check the bleed lines and check valves.
If it hasn't seen a fuel pump kit in a couple of years, put one in.
Bubble test the fuel suction line. (looking for air leaks.)

I avoid gasohol at all costs. 91 octane here is non-oxygenated. Don't need the octane, but it doesn't hurt.

Yer right, that engine be a screamer.

hope it helps
John
 

Nachman

Cadet
Joined
Jun 4, 2010
Messages
10
Re: 88 Merc XR4 150 Troubles

Thanks Admiral! I'll make some general health checks and go for the fuel pump. Will keep in touch. Thanks for the response...you set me right on my warn horn Q, and Texas BBQ is on the house!
Thanks again.
Dave
 

Titanty

Seaman Apprentice
Joined
Apr 6, 2010
Messages
36
Re: 88 Merc XR4 150 Troubles

Nach,
Good luck getting her runing right. I just bought my first boat with the same motor (1990 model). So far it's been real nice, with minor issues. On mine the first things I had to fix was hoses and plastic cap on the oil res.

I actually took mine to a shop for a complete tune up since I just don't know much about outboards. IMO, it was the best $300 I spent on it so far.
 
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