1989 Johnson Seahorse 150 questions

[MASTER Brian]

I am looking at buying a 1989 Ranger 363V 18' fish/ski boat that has this motor on it.<br /><br />Is this a good motor for this size/type boat?<br /><br />What compression should this motor have and what is the best way to check compression on these motors? When I check compression on 2 stroke jetski's the plugs need to be grounded to the block so that you don't fry the coil, is that the same for these motors as well? I don't want to fry anything, especially before I buy. <br /><br />I'm also curious what spark plug this takes or what the plug size is, so that I can make certain I have the correct adapter for my compression tester on hand when I go to look at the boat.<br /><br />Are there any other things to check for when looking this motor over? I've been told that these motors sometimes had issues, because the rings were too high on the pistons, any truth to this? This is why I want to run a compression test.<br /><br />Thanks for any info...

 

[OBJ]

Re: 1989 Johnson Seahorse 150 questions

Welcome to iboats Brian!<br /><br />Is this a good motor for this size boat? If it's set up correctly, should do well.<br /><br />Do get compression readings on all cylinders. The higher the compression, the better. What's more important is how close to each other the cylinders are. It is recommended that the cylinders be within 10>15% of each other. If all the cylinders are in the 90's, I would think the engine block is good to go.<br /><br />Use only Champion spark plugs. The recommended plug for this engine is the QL77JC4 gapped at .030. For a better low end idle, gap them at .040. Won't hurt top end.<br /><br />Check the spark on all cylinders. They should jump a 1/2" gap with a hot lighting like spark.<br /><br />Check the gear case lube for any signs of water intrusion.<br /><br />Get a maint. history off the owner. When were the carbs last rebuilt, when was the water pump impeller last changed out and does the block run at temp, any known current problems. Get a ride. See how it does through the throttle range. Look for a smooth transition idle to WOT.<br /><br />Don't be afraid to ask questions of the owner. It's your money your putting down.

 

[MASTER Brian]

Re: 1989 Johnson Seahorse 150 questions

Thanks for the info, that will be useful. I have talked more with the current owner, it's a boat that came from insurance as a theft boat. I guess they took the electrics, trolling motor, motor, etc. The guy selling it put this motor on, I'm not sure how old the motor is, but he said it runs strong and is willing to take me out in it. I'll ask about the motors age, he did say he'd guarantee the motor, but didn't say for how long. Runs a tractor business and sells used boats.<br /><br />I'll check the gear case lube, but it doesn't sound like it's been on the water for some time, probably a year or two and not positive with the current motor. Which begs the question, how do I know the motor has been set correctly on the boat? Do I just pay attention to how it handles on the water, speed and handling wise?<br /><br />Thanks again...

 

[ezeke]

Re: 1989 Johnson Seahorse 150 questions

You could take a lot of risk out of your purchase by hiring a marine surveyor to look the boat and motor over for you, and possibly to go with you on the test run.<br /><br /> Marine Surveyors <br /><br />Good Luck!

 

[MASTER Brian]

Re: 1989 Johnson Seahorse 150 questions

I appreciate that advice, but the nearest one that link came up with was 800 miles away. For the price of this boat, that's not justifiable.