Switching powerheads

[FlaCowboy]

I have been lurking the forum for awhile now and would like to commend those of you for sharing the knowledge you have with those of us without the knowledge. This is my first post of what I am sure will be many more since I am one of those without the knowledge...lol.
I recently bought a 1990 TideCraft WideFire Bass Boat with a 89 Johnson 150 J150STLCEM model. I knew when I bought the boat that it had motor issues. I am going to rebuild the powerhead, however, I just saw a 87 Johnson GT150 complete powerhead for sale at a resonable price. My question is will this powerhead bolt on to what I have, if so will I need any special adaptors?
I am in no way a mechanic but this is something that I want to do with my son. So if you take the time to reply please keep that in mind and explain it as easily as possible.

Thank you in advance

 

[milliesdad]

Re: Switching powerheads

Personally, if I was planning on rebuilding the power head, I wouldn't go out and buy a motor with a questionable history.Might end up rebuilding that one.

I'd rebuild the 89 150 HP, incl rebuilding carbs. Then you know what you have.

 

[dehydrated]

Re: Switching powerheads

They will bolt up the same in answer to your question

 

[emdsapmgr]

Re: Switching powerheads

About the only difference between the engines is in the electrical. The 87 has dual power packs, the 89 has a single-with quickstart. The 87 has the large 35 amp alternator, the 89 is the smaller 9-10 amp variety.

 

[1946Zephyr]

Re: Switching powerheads

With a rebore and new pistons/rings, you're talking around $1200 for everyhting. If the cylinders are good, then that's a big savings on your part.

 

[FlaCowboy]

Re: Switching powerheads

Thanks folks for the input. The only reason I was thinking about switching powerheads is the time frame between rebuilding vs switching and getting out on the water. It has been about 15 years since I have had a boat therefore I have that itch to get back out asap. I went ahead and made the decision to rebuild. I started yesterday afternoon around 3 and just finished the disasembly. I have pictures that I will post later. I bought the boat several weeks ago knowing the previous ower had overheated the engine when the water pump went out while he was on the water. I plan to rebuild this thing from the steering wheel back so this will be a slow process seeing how I work out of town thru the week.
What I found when I took it apart is this...on the right bank ( standing behind the engine ) the center piston looks like it has been sand blasted. The cylinder walls feel and look more like there is a build up on the walls rather than scratched. Looking at the heads the middle one has alot of light grayish buildup on it. However the top head is pitted. It looks more like it is damage from something previous. There are no markings on the top cylinder or piston or any other ones for that matter. I will be going back out of town early in the morning so there is not much else that I can do until next weekend. What I would like to know for the time being is this. I want to clean the block as much as possible before it goes to the machine shop. There is some corrosion in the water areas that I would like to get cleaned out. Nothing heavy but enough that it needs to come out. Any ideas what to use or how to get it out?
Again...I will post some pics in just a little while....wife says it is time to start the grill.

Thanks for any input or replies.

 

[dehydrated]

Re: Switching powerheads

take alot of pictures and put them on here you will get more specific answers .

 

[emdsapmgr]

Re: Switching powerheads

Possible the starboard center piston suffered from lack of lubrication. When this happens it is not unusual for the aluminum of the piston skirt to transfer to the cast iron cyl walls. You can clean this aluminum transfer off the walls with some muratic acid. Dents in the piston crown are probably from the upper ring which let go and got pounded between the head and the piston top. You need to determine just what cause the failure so it does not occur when you start up the rebuild powerhead. I'd be pulling that center carb apart and visually inspect the side of the carb that feeds that bad cyl. You may find some dirt/debris clogging the high speed jet, causing your problem. If you have water corrosion in the powerhead, keep in mind it is also in the heads-pull the head covers off the heads for a visual inspection. Also check the valley between the V-banks of the powerhead-you will have to remove the voltage regulator to have a look.

 

[FlaCowboy]

Re: Switching powerheads

Thanks for the input. Here are a few pics, I had more to upload but I suppose they were too big. Anyway the center piston on the right back is the issue. The rings are in tact, however the side of the piston is scratched as though something got into the cylinder. I will not have a chance to pull the carbs apart until this weekend. All cylinders were oily including the one in question not as oily but not completely dry either.

 

[1946Zephyr]

Re: Switching powerheads

That one cylinder looks pretty rough. looks like a bore job is in order.

 

[FlaCowboy]

Re: Switching powerheads

That one cylinder looks pretty rough. looks like a bore job is in order.

Hi Zephyr,
actually the wall does not seem to be scratched. This is some type of build up on the wall. The sides of the piston itself is scratched and what it seems to me like is the shavings from the piston melted to the wall of the cylinder. Anyone ever see this before?

 

[dehydrated]

Re: Switching powerheads

a little muratic acid on a q tip will clean it off the walls not too much at one time keep it cleaned off as it will eat aluminum . look for deep scratching with your fingernails you might of gotton lucky and of caught it soon enough . The only way to know for sure is to have it checked out at the machine shop. My .002 worth you have a lean condition on # 3 Time to also rebuild carbs and replace all fuel hoses

 

[FlaCowboy]

Re: Switching powerheads

Thanks for the info. This engine has already been bored to .030. Once I clean the aluminum from the cylinder wall should I hone it? If so, then what size honing tool should I use and is there any certain rpm the honing tool should be used at? Does this process require using oil as it is being honed?

Thanks again for any info and all input.

 

[emdsapmgr]

Re: Switching powerheads

You will need to rehone all the cyls-assuming that you will put new rings on each piston before reassembly. It is possible that the middle cyl overheated. I can't get a look at the rubber water diverters in the blocks from the pictures you posted. Any chance you have pics showing the placement of those diverters?

 

[FlaCowboy]

Re: Switching powerheads

Hi emdsapmgr,
all of the water diverters were in bad shape and will be replaced. I am posting some more pics of what I found when taking this engine apart and where I am now. The first pic is of the piston that is the problem. It got scratched and the shavings melted to the cylinder wall. Rings were still intact but scratched also. I honed all cylinders which brings me to these questions. I am no mechanic and what I need to know is since I honed all cylinders ( not sure if I honed them all equally ) is there any way to measure the cylinders or are rings a standard size? I plan on replacing all pistons, rings, bearings and water diverters. Anything else that I need to replace while the engine is completely apart?

Thanks again for all info and input.

 

[Faztbullet]

Re: Switching powerheads

Classic case of preignition, last picture of piston shows "eyebrow" eroded away, timing or lean on that cylinder. Before you spend anything on this ,mike the cylinders and if they are more than .003 out of round you will need to bore it oversize. If it was bored .030 your spec's are 3.530 and if you do bore the only pistons larger are aftermarket and I dont suggest Wiseco's.I also do not see any crosshatch in the hone job and looks to been with a "ball" hone...

 

[dehydrated]

Re: Switching powerheads

need to get clyinder bore gauge to measure roundness check your local tool rental business or local pawn shop is where i found some.rings are sized in your case i think the standard bore is3.50 if im not mistaking.replacing all the bearings can get expensive but hey why not i would replace the wrist pin bearings and inspect the others for replacement just my .02 worth

 

[emdsapmgr]

Re: Switching powerheads

The factory makes ringsets to go with their oversize pistons. In your case, your pistons are already .030 over, so get a 5 sets of .030 rings. They will work in your bores. They will seat in your cyls-once they are honed properly. You will need one new .030 over piston. Bombardier includes a ringset in the box with each oversize piston. Your bad cylinder was running without proper lubrication, either from fuel/oil starvation or from overheating. I think you would see a problem on all cyls if the timing was incorrect. The correct way to overhaul is to overbore when the cyls get out of factory spec, as Fastbullet indicated. If you need to go to up to .040 over, you get into other issues, including having to rejet that side of the carb. I'd be inclined to overhaul and run it the way it is, even if you find you have slightly oversize bores. Your engine should break in fine and run normally-bascially running with slightly oversize bores reduces your long-term engine life.