Should you pull the engine to rebuild or not

rkkoeb

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#1
So I have a 98 speedster and last year the compression was about 130 on each cylinder. With that said I decide to rebuild the engines this spring. Couple of questions, first should I just do the top end or the complete motor? I have no idea on the hours on both engines but after will install an hour meter. I was told that I should just look at the top end rebuild. Second, should I remove the engines to do the rebuilds or just do them in the boat? I understand that taking them out will require me to have to align then again using some type of tool. How hard is that to do? What tool would I need and how much are they? If I take the engines out I will clean the inside of the engine compartment but if I leave them in I will save some work of having to take them out and putting them back in. Any suggestions on what people have found to be easier to do?
 


jhjesse

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#3
Yes pull the engine. Yes you will have to realign but it is not hard. It is way easier than working upside down in the engine compartment.
My opinion is do a full rebuild with older engines.
Pulling the engines allows you to get at everything. Just makes a neater cleaner job.
 

jts32

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#4
A lot of things to consider, and ultimately depends on your intentions for the boat and conditions of the motors.

If you plan on keeping it for a number of years, I'd pull the motors, do complete rebuilds and clean everything up. This requires more work, money, and special tools. You'll need an alignment tool, flywheel puller, impeller/pto tool, and degree wheel. End result would be a hopefully reliable boat for many seasons.

If you plan to get rid of the boat in the near future, and the bottom ends are good(bearings and seals), I would just do a top end rebuild in the boat. Depending on the condition of the cylinders and pistons, you may get away with just replacing the rings(doubtful, but wishful thinking). No special tools needed, less work, and less money. It is a PITA working in a cramped space, especially a twin engine. Remove the engine cover, and most of it can be done kneeling on the swim platform and leaning in.

I personally prefer to pull the motors and go through everything, but I also have all the tools needed. I also can't stand a filthy engine bay, and removing everything allows me to pressure wash 20 years of grime away. Good luck.
 
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mikidymac

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#5
Even if I wasn’t doing the crank I would at least pull the engine and replace the crank and rotary seals and intake o-rings. It’s very common for older engines to develop air leaks as the rubber degrades.
 

jhjesse

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#6
Anyone ever installed wrist pin circlips upside down in and engine bay?
 

rkkoeb

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#7
How hard is it to replace the crank and rotary seals? Do I need any special tools to do this job? I am pretty sure I will pull both engines this way I can clean the inside of the engine compartment and also paint the engines when they are out. I am not sure how long we will keep this boat as it is our first boat. The only reason I would sell it would be to upgrade to a 4 stroke speedster but that is a lot of money to spend.
 

jts32

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#9
No special tools to replace outer crank seals. For the RV shaft, you will need a snap ring pliers and make a puller out of threaded rod. You will also need a press to remove/install outer RV shaft bearing to replace the seal
 

Sandman251

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#13
Looks like I am the only one wondering why you are rebuilding running motors just because they only blow 130psi. First, I would double-check those compression numbers with a different gauge that is known accurate. Although it could happen, I would be suspect of BOTH motors being down exactly 20lbs. If those numbers end up being accurate, why not just run the thing like you stole it? Who cares? Even at 130psi, that boat should STILL be running low to mid 50's. Those 787's could run strong 25 hours a year for many more years. If you're feeling like you MUST do some maintenance, go through the carbs.... whatever. Anyway, just my nickel's worth.
 

jhjesse

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#14
I agree, but the OP wants to rebuild his engines. It is his boat. Just trying to say if it’s going to happen pull the engines vs. working upside down in the engine compartment. When I had my boat, it seemed like I was always upside down.
 

rkkoeb

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#15
I will check the compression again once I get my boat back out of storage. I guess I was just trying to be proactive with the motors and keeping them fresh
 

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