New to me Regal Rush, low compression in number 3

[Drew Caplan]

I just picked up a 1997 Regal Rush with a Force 120 engine. The boat is in immaculate condition and I got it for a really great price. Cylinder 3 has compression of 60 psi (other around 150). In the past I have worked on many different kinds of engine but with this one a few friends had said it is likely just a stuck ring and to use PB or something like that to free it up. The question I am facing is should I do this or just tear into it and replace the rings while affording me the opportunity to check out everything else and replace the gaskets/rings on all cylinders.

 

[jcyamaharider]

Have you checked the oil lines to make sure they are still on the carbs/cylinders? I worked on one and it worked its way off and fried the cylinder. A conversion over to pre mix may not be a bad idea.

 

[4x15mph]

I would pull of the carb(s) and clean them. I would also pull the engine head off and take a look with the probability of having to do at least a top-end rebuild. Once you score the cylinder which may already be the case, you may have to bore it out or get a sleeve.

Definitely check that your oil lines are secure and once you have it running, check that you are getting oil into each cylinder. I like oil injection unless you know that it is compromised already.

That's a great find given that is probably pretty rare. Keep us posted on the upgrades and maiden voyage.

 

[Drew Caplan]

Thanks guys, I really appreciate the help. This weekend I will pull the head off and look at each cylinder to see how they look. I like the idea of sticking with the oil injection but I am not sure the best way to test it. Should I just watch the oil level or would a more proactive approach be to pull the line off for a second to see if there is oil being delivered? I figured I would keep an eye on the oil level as I fried an ATV a few years back after the pump stopped working on a ride without my knowledge.

I paid $400 for the boat and the trailer which was an absolute steal. The engine is clean and looks brand new and there isn't even a tear or much wear on the seats. It was owned by the same person since brand new and garage stored every year. Downside is the owner didn't know much about boats and didn't fog it properly every year.

 

[Cobra Jet Steering LLC]

Look for signs of discoloration caused from overheating, this is the main reason a top cylinder looses compression as it runs the hottest. Usually the paint on the head will be " darker " looking. If it ran hot it most certainly warped the head and will leak water into the cylinders, check end play also just to get an idea of the condition of the rod bearings. Remove all spark plugs , rotate the engine by hand at the flywheel, watching for the pistons to come to top dead center , when a piston passes the point of t d c and starts to go back down the cylinder, stop moving the flywheel , use a screwdriver and push on the top of the piston, if it is tight you are fine if you feel a clunk and then it gets tight you have play, you don't want play that means the bottom end needs work. Ignore it and eventually you have the pleasure of throwing a rod through the block.

 

[4x15mph]

Is there a flame arrestor on top of the carb(s) or an air filter? You should be able to pull that off and look down the throttle body of the carbs. While it is running look for oil feeding into each carb. I don't know anything about that engine but this is the idea. You would want to have the engine running first. Also, if the oil lines aren't secured with wire or clamps, I would secure them asap.

 

[RiverRat]

I've wasted 400 bucks on waaaay less awesome things. Congrats and good luck! Can't wait to hear about you flyin around the lake on that thing!

 

[biglar155]

Wow, for $400 you did great! Welcome to the Jetboat club!

 

[Drew Caplan]

Look for signs of discoloration caused from overheating, this is the main reason a top cylinder looses compression as it runs the hottest. Usually the paint on the head will be " darker " looking. If it ran hot it most certainly warped the head and will leak water into the cylinders, check end play also just to get an idea of the condition of the rod bearings. Remove all spark plugs , rotate the engine by hand at the flywheel, watching for the pistons to come to top dead center , when a piston passes the point of t d c and starts to go back down the cylinder, stop moving the flywheel , use a screwdriver and push on the top of the piston, if it is tight you are fine if you feel a clunk and then it gets tight you have play, you don't want play that means the bottom end needs work. Ignore it and eventually you have the pleasure of throwing a rod through the block.

Thank you for the advice, it isn't the top cylinder, it is number three which is second from the bottom (it is a 4 cylinder). I looked and there is absolutely no discolouration of the paint so I think I am safe there. Looking at this engine if I want to replace the rings the cylinders are one piece with half of the lower so if I pull them off I have easy access to the crank anyways.

First things first though is to do a little more investigation at the head.

 

[Cobra Jet Steering LLC]

ok good, the head may just have a bad gasket and the rings may not be messed up so pulling the head may be the fastest way to see what the problem is.
Those were notorious for frying the brain, I had one and I figured out what the cause of the problem was and how to protect it from happening so when you get it all fixed I can tell you what to do to keep it from having that issue.

 

[Drew Caplan]

ok good, the head may just have a bad gasket and the rings may not be messed up so pulling the head may be the fastest way to see what the problem is.
Those were notorious for frying the brain, I had one and I figured out what the cause of the problem was and how to protect it from happening so when you get it all fixed I can tell you what to do to keep it from having that issue.

Thanks for all the advice, reading past threads you seem to be a good knowledge base! If you don't mind me asking when you say 'brain' are you referring to the engine in general or something specific on it? Also, if you don't mind sending some info along for what you did to your engine that would be great! It is hard to find info on these engines really. There are a lot of parts readily available on eBay which is great. As long as I can keep the major pieces in working condition I don't mind doing repairs here and there. I will post some more photos today.

 

[Geiger41]

WOW lets see some more pictures !!

 

[Bilmon]

If you need a manual http://www.boatinfo.no/lib/mercury/manuals/90-120_sportjet.html#/0 Looks like a great find and welcome aboard

 

[Drew Caplan]

If you need a manual http://www.boatinfo.no/lib/mercury/manuals/90-120_sportjet.html#/0 Looks like a great find and welcome aboard

Thanks, I was kinda stupid and ordered one from ebay for $15.00... I should have looked here first! lol

 

[Cobra Jet Steering LLC]

The brain is what I call the ignition module, also remember N A P A autot parts carries small engine parts for those older force power heads including electronics, however I should qualify that and say that was many years ago back when I owned one . But it can't hurt to check on that since their prices were very reasonable. Tell them to look in the small engine parts catalog if you check because most of the counter help probably has no idea that they handle marine parts. People will tell you that you need the new stator to avoid the problem but that is not correct I had a new stator and it still fried the brain, like I said when you get it running I will tell you how to avoid having your ignition get fried due to a design flaw in the electrical system, it's simple and inexpensive.

 

[Drew Caplan]

Here are some more photos after the first light clean. It will be getting the full scrub down this weekend.

 

[Cobra Jet Steering LLC]

If you follow the link and click on the bottom video you can see my regal rush jet boat, the video can be expanded since it is condensed, that was the actual boat that got me started in 2001 on the path of fixing handling issues with jet boats.
http://www.cobrajetsteering.com/index.php?option=com_content&view=article&id=60&Itemid=67

 

[Drew Caplan]

If you follow the link and click on the bottom video you can see my regal rush jet boat, the video can be expanded since it is condensed, that was the actual boat that got me started in 2001 on the path of fixing handling issues with jet boats.
http://www.cobrajetsteering.com/index.php?option=com_content&view=article&id=60&Itemid=67

The videos are in an old windows format that you can't play on a mac but I will convert them and have a look! Thanks for all of the advice so far!