johnson v4 150 1995

[Michael Healy]

Motor intermittantly bogs down when running at cruising speed. Seems to be firing fine, but not getting good fuel supply. After a few minutes it usually catches, and runs normally for awhile before bogging down again.

Recently it ran at idle speed all afternoon with no problem. Started to have problems when making the run back home.

Thanks,

Mike

 

[HighTrim]

Re: johnson v4 150 1995

Welcome to iboats Michael. I would start by check the spark and compression to ensure that you have a bright blue spark that will jump a 7/16 of an inch gap on all cylinders and you have a viable base to work with in regards to compression, around 100 psi on all cylinders and within 10 percent of each other. Let us know if you need help with these procedures. If you have good spark and compression, I would move on to fuel delivery. Test by spraying some premixed fuel into the carbs when it is acting up. Does this improve things? How about pumping the primer bulb, does this pick it up? Let us know what you find.

 

[w2much]

Re: johnson v4 150 1995

Fuel tank vent, fuel connector O ring.Had the same issues went all around the electrical found nothing . I overlooked the obvious. For me it was a $5.00 part. Still, check your spark. Good luck.

 

[HighTrim]

Re: johnson v4 150 1995

Very well could be the anti syphon valve as stated, they are notorious for sticking in the semi closed position. If that is the case, you will need to remove it of replace it. As far as fuel delivery goes, try this test out.

Get a vacuum gauge and hook it inline on the fuel hose before the engine, along with a clear section of hose. Take it for a spin, noting the readings and monitor the fuel flow through the clear hose.

Findings:

-Vacuum of less than 2 inches and air bubbles in the clear hose indicates an airleak into the fuel system
-No air bubbles and less than 2 inches indicates a bad fuel pump
-Vacuum over 4 inches indicates a restriction.

Sample gauge

"http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=STRK%3AMEBTOX%3AIT&viewitem=&item=4610113711&_trksid=p3984.cTODAY.m238.lVI"

 

[Dhadley]

Re: johnson v4 150 1995

Mike, lets start from the begining. There are a couple of 1995 V4s and a 1995 150 V6. Which do you have?

 

[Michael Healy]

Re: johnson v4 150 1995

Thank you for your reply. Where is the anti-syphon valve located? Due to the intermittant nature of the problem, it seems like a likely suspect, and inexpensive to repair/test.

Very well could be the anti syphon valve as stated, they are notorious for sticking in the semi closed position. If that is the case, you will need to remove it of replace it. As far as fuel delivery goes, try this test out.

Get a vacuum gauge and hook it inline on the fuel hose before the engine, along with a clear section of hose. Take it for a spin, noting the readings and monitor the fuel flow through the clear hose.

Findings:

-Vacuum of less than 2 inches and air bubbles in the clear hose indicates an airleak into the fuel system
-No air bubbles and less than 2 inches indicates a bad fuel pump
-Vacuum over 4 inches indicates a restriction.

Sample gauge

"http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=STRK%3AMEBTOX%3AIT&viewitem=&item=4610113711&_trksid=p3984.cTODAY.m238.lVI"

 

[Chris1956]

Re: johnson v4 150 1995

Mike, the antisiphon valve is usually located in the fuel tank pickup fitting. On my boat, the pickup tube that goes to the bottom of the tank unscrewed from the elbow. The A-S valve was under this tube.

 

[ezeke]

Re: johnson v4 150 1995

Almost all built in tanks that have a anti-siphon valve have them in the outlet fitting where the outgoing fuel line attaches. Most consist of a spring and stainless steel ball bearing.

BTW, OMC did not have a 150HP V4 in 1995.