1989 GT150hp hard start

1989 GT150 takes awhile to get going. Once she fires, she runs fine (turns normal rpms at WOT and has normal strong power throughout the range, no hesitation) and will start at the slightest bump of the starter for the rest of the day. After attempting to start it for a while, the top plugs are dry, middle are damp and the lower are wet. Ideas?

Re: GT150 hard start

Is this your cold start procedure?

Pump fuel primer bulb up hard. Apply a slight bit of throttle to take throttle butterflies off idle setting. Turn key to START position..... and push key in and hold it there at the same time to activate the primer solenoid. When engine fires and starts, release key from START position to ON position.

If so, the engine should fire and start within 6 revolutions.

If not, what is your starting procedure?

Re: GT150 hard start

That's pretty much the standard procedure for any outboard I've ever run except that this GT150 likes a little throttle with choke in warm weather but no throttle when it's below 50 or so out. For the six years I've had it it's always fired within 3 seconds or so, until about a month ago. This appears to have gotten progressively worse, now taking a good 8 to 10 five second tries to get it cranked unless I use a shot of starter fluid (made for 2 cycles.) Then it fires right up, runs rough for a few seconds then smooths out. It would appear the top carb isn't getting fuel at first since the top plugs are dry (do these carbs have individual anti-siphon valves or is there just one in the system - maybe this one is siphoning somehow and is dry at first?)

Re: GT150 hard start

When was the last time the carbs were cleaned & new kits installed?

Re: GT150 hard start

While I've replaced every electrical component on this engine (several years back,) air/fuel delivery has never been an issue until now so the I've not touched the carbs except to sync them a few years ago. I find it hard to blame this on an internal carb part (except for something that prevents siphoning) due to the fact it performs flawlessly at idle, acceleration, WOT operation and cranking (after the first time that day.) Rebuilding the carb would be, of course, a default action but I was looking for any specific ideas on what is going on.

Re: GT150 hard start

The condition of the spark plugs..... Dry, Damp, Wet, would indicate carburetor problems. They do tend to foul over a period of time, and the top carburetor would be more subject then the bottom one.

However...... first check the compression which shuld be approximately 100+ psi and even on all cylinders. Then, with the spark plugs removed, check the spark which should jump a 7/16" gap with a strong blue lightning like flame.... a real SNAP! The 7/16" gap is important. Checking spark by using the spark plugs is a waste of time.

Now, trace one of the small hoses that lead from the primer solenoid to either the carburetor(s) or intake manifold (forget where they end up on that model) and pull one loose. Pump the fuel primer bulb up hard. Now, while watching the loose end of that small hose, turn the key to the ON (NOT START) position and push the key in. Fuel should shoot out of that loose hose..... if it does not, threin lies your problem.

If the compression, spark, and the primer solenoid fuel flow checks out, that leaves the carburetors.

Re: GT150 hard start

I've checked the spark with an inline bulb gauge (I've found over the years it is much easier to compare the brightness of a bulb than to guess at the brightness and intensity of a spark jumping a gap) and the compression is right at 85 psi on all cylinders (remember these GTs are 'low compression' engines, they are the exception to the normal compression numbers, 85 psi on one is as high as they should be.) But again, this engine fires right up with starter fluid and runs strong thereafter, no it is not an ignition problem.
I was staring at the primer solenoid this afternoon and thought about but didn't have time to do exactly what you are suggesting. I replaced the solenoid a few years ago due to a leaking o-ring on the adjuster. I'll try to find time tomorrow to make sure it is giving a shot of fuel to the top carb.

Re: GT150 hard start

georgia-dawg said:

While I've replaced every electrical component on this engine (several years back,) air/fuel delivery has never been an issue until now so the I've not touched the carbs except to sync them a few years ago. I find it hard to blame this on an internal carb part (except for something that prevents siphoning) due to the fact it performs flawlessly at idle, acceleration, WOT operation and cranking (after the first time that day.) Rebuilding the carb would be, of course, a default action but I was looking for any specific ideas on what is going on.

Click to expand...

If you own Outboards long enough you should now know the is never any "specific ideas" Pull the carbs clean and rebuild em if you have to and go from there ..

Re: GT150 hard start

Just replacing or rebuilding things to try to cure an issue without really understanding what is wrong has cost anyone and everyone at some point money and time that they later found out was a waste. If you've got a week or two to kick something around to figure it out, you not only save money, more importantly you learn more so that next time you know more.
This time, it was just a simple hose from the primer solenoid that had hardened and was restricted from a bend not visible until it was removed. Problem solved with just a foot of fuel line that was already lying around.
BTW, this engine has been run weekly since I acquired it six years ago. Hot or cold, I fish, therefore I am.

Re: GT150 hard start

Glad it all worked out for you, thanks for the feedback..