1987 Suzuki DT85 overheats at high RPM

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

After first managing to lose the motor cover off my 'kicker' (a mid 60's Johnson that belonged to my grandfather) on the drive to the lake, I think we made some headway.

I ran for quite some time at WOT without the alarm. At one point, I pulled the motor cover and checked the block and it felt pretty warm, but the alarm did not sound. Water pressure seemed to hover around 5-7 psi at WOT. After some more running, the alarm finally sounded, but when I checked my improvised cover over the intake it had been pulled free. It sure seems like you nailed it, mphelle8vld.

I'll either purchase the OEM cover for that intake or come up with something more permanent.

When I first got the motor, it had a 'whale tail' mounted to the cavitation plate. I wonder if I should re-install that?

You asked for a photo of the lower unit and transom of my boat. You can find that attached. As you can see, the cavitation plate is basically even with the bottom of the boat.

 

[mphelle8vld]

Re: 1987 Suzuki DT85 overheats at high RPM

Great news! You really stuck with this one. I would play around with load and balance, try the whale tail, smoke a cigar, and then look at sizing the prop. I believe it's around 200rpm per in of pitch. Keep us posted.

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

Yeah, I stuck with it, but I never would have guessed to block that intake. Thanks for your efforts - they were a huge help.

I'll be sure to give an update when I've got things 'dialed-in'.

 

[fish4970]

Re: 1987 Suzuki DT85 overheats at high RPM

There should be a thread on here that I posted a few years ago, I had the same problem with mine. I only found the problem after I tosted the motor trying figure it out. Durring the rebuild I found the gasket between the the motor and the lower unit had corroded, there are small holes where tje water is supposed to spray in the exhaust had rotted out tobe large holes and the water flowed too freely out the exhaust and not allowing Iit to reach the top cylinder. After I replaced that gasket and rebuilt the motor, I have had no more problems

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

Interesting that someone posted today. I was actually out with the boat yesterday and am still struggling with water pressure issues.

First, let me discuss your suggestion, fish4970. Are you referring to the 'motor holder gasket' which the motor sits directly on? I've actually replaced that gasket twice during this exercise. There appears to be another gasket below that, between the engine holder and lower unit that I have not replaced, but I think at that point, the water is still in a tube being transferred up to the manifold in the engine holder.

I permanently mounted a water pressure gage on the boat so I could keep an eye on this issue.

I've altered the water intake cover on the bottom side of the cavitation plate so it is effectively a cover. I've also played with covering some of the top slots on the other water intakes going on the theory that the motor is sucking air. Yesterday I had the top two slots covered on the intakes and could not maintain pressure at all. I even pulled the water tube off the gage when running and found the water to flowing in a slow, hot stream.

Last evening I fabricated some 'scoops' that I mounted over the water intakes that will hopefully force some additional water into the system. I'll be trying this out today.

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

I took the boat out today and the new 'scoops' I added over the water intakes didn't seem to help much, if any. So, I'm back to where I was - decent water pressure sitting on the driveway with muffs or sitting at the dock. But once I get underway, water pressure drops to 5psi or less.

Given the number of things I've tried to get water to the pump, it seems like there has to be something after the pump. I dropped the lower unit again this afternoon and checked out the seals on the water transfer tube that runs up between the pump and the bottom of the motor. The seals on it look OK. However, fish4970's post got me looking closer and it doesn't seem to run all the way up to the bottom of the motor. Maybe there is something bad in that area?

I'm working at pulling the driveshaft housing, but that seems like its going to get involved.

I'll post more as I get further along, but any further input from fish4970 or mphelle8vld would be welcomed.

 

[mphelle8vld]

Re: 1987 Suzuki DT85 overheats at high RPM

I think fish4970 provided the next thing to check by dropping the driveshaft housing. You should be able to check the castings and gasket (12). The tube only runs up into the driveshaft housing. http://www.**********/parts/search/Suzuki/Outboard/1987/DT75TCLH/Engine Holder/parts.html

The link wouldn't work, look for a parts diagram and click on engine holder.

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

Yeah, unfortunately, I agree. After pulling the water tube, it's obvious that doesn't make it all the way up to the 'engine holder'. It also appears that in order to get the driveshaft housing loose and examine/replace the gasket (12), I'm going to need to pull off the engine - again. Maybe when I go out and stare at the motor again today I'll figure out a better way. Thanks, both of you, for your input.

As I'm tearing into this engine again, I keep seeing the perfectly good 50hp motor I have sitting in the corner of the garage. If I had good sense, I'd just put it back on....but I don't like to lose.

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

I'm stumped.

I have the drive shaft housing loose from the bottom of the engine holder, but it cannot drop free because its held by the Exhaust Tube (13 on Engine Holder Diagram) and the Lower Mounting Bracket (15 on the Drive Shaft Housing Diagram).

I have the bolt (11) loose that holds the Lower Mounting Bracket to the Drive Shaft Housing. It looks to me, like if I take off the nut (19 on Drive Shaft Housing or 6 on the Swivel Bracket Diagram) off the steering bracket (5 on Swivel Bracket Diagram), I should just be able to push the Lower Mounting bracket down off the steering bracket and the drive shaft housing will just come with it. Alternately, I should be able to just pick up the entire entire engine/lower unit by the Steering Bracket. However, I can't get the Lower Mounting Bracket to budge off the lower rod on the Steering Bracket.

I've tried to get a puller on the lower mounting bracket, but I can't get a good grip due to geometry of the casting. I've also tried to drive a wedge between the main motor bracket and the lower bracket and it won't budge.

I took out the little rubber thrust cushion (8 on the Drive Shaft Housing diagram) to see if perhaps there was a set screw hiding back behind there, but I didn't see anything.

What am I missing?

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

I managed to get the drive shaft housing off by loosening the bolts for the Exhaust Tube so everything could drop free. Of course, two of the 6 bolts twisted off, so I'm going to have fun fixing those.

Anyway, the gasket between the driveshaft housing and engine holder was a mess. Thanks fish4970 for steering me in that direction. And, thanks to mphelle8vld to sticking with me.

I'm still not sure how to get the Lower Mounting bracket loose. I think it would be much easier to re-assemble everything if I could get that off.

 

[mphelle8vld]

Re: 1987 Suzuki DT85 overheats at high RPM

I'm at a Fathers day get together so borrowed an ipad to check in. That bracket has been on there for 26 years, I would soak it with pb blaster while you're working on the twist offs, maybe some heat and a rubber mallet if you have touch up paint. I doubt you want to pull the powerhead again.

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

Your post cracked me up. I told my wife she couldn't be mad at me for working on the motor today - it's Father's Day and I get to do what I want. I can't imagine the explanations I'd have to conjure up to check a post from a Father's Day gathering.....

I DO NOT want to do much disassembly again and will figure out a way to put everything back together even if I don't get the Lower Mounting Bracket broken free.

 

[stylesabu]

Re: 1987 Suzuki DT85 overheats at high RPM

so was it the bad gasket?

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

The gasket appears to be corroded through in places. I have a new gasket on order, but am still waiting for it to arrive. Parts for this Suzuki motor always are available, but don't seem to be stocked in distribution so getting them generally takes a week, or so.

I'll be sure to post when I get everything back together.

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

The new gasket did not fix the problem. As bad as that gasket looked, I cannot believe that wasn't the issue. I'm rapidly running out of time to get this motor fixed before taking a day 10 trip.

I believe I have now repaced every gasket in the motor that has contact with the cooling water.

There are two 'seals' on the tube that runs the water up from the pump to the power head. The top seal looks a litte rough, so I'll try testing out a way to get a better seal on that joint.

The water pump was been by a mechanic just before I acquired the motor and then I rebuilt it once myself. The wear surfaces in the pump didnt' look bad to me, but maybe I'm not seeing something. I'm going to try and rig something up so that I can spin the pump while the lower unit is off the motor and check water flow/pressure. Maybe I can get the pump to show something odd.

I'm completely open to any other suggestions. I have to either fix this motor or pull it off this weekend and put the old one back on.

 

[mphelle8vld]

Re: 1987 Suzuki DT85 overheats at high RPM

Strange that the problem seemed fixed with the upper cooling inlet plugged and now it has returned. Is it possible it's a loading/balance issue that has the motor too high while on plane? You mentioned the motor was mounted higher than recommended and it looks like it's as low as it can get, how does your 50hp compare to the 85hp measuring from the hooks of the mount to the cavitation plate?

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

I'm just not sure the problem was really 'fixed' when we covered the water inlet on the cavitation plate. Isn't 5psi still very low for a motor? And, recall that I've played around with covering intakes and even built scoops to help pull water in to address the potential issue of mounting height. I was even losing pressure last weekend before getting up on plane.

I was reading around last night and saw numerous posts with regard to OMC motors that had bad 'water tube grommets' which resulted in low, or no water pressure. The top 'grommet' on my water tube isn't in the best shape. It's certainly not in nearly as good a condition as the lower 'grommet' that inserts into the pump housing. I was having a hard time measuring the diameter of the hole the water tube inserts into up in the casting - I wish I had some pin gages. It seems hard to believe that this could be the source of my problems, but there isn't much else to look at.

I'll post more later this week.

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

Since my last post, I've re-worked the 'grommets' on the water tube and replaced the water pump housing - both without any benefit. As a matter of fact, I think the motor is having a harder time holding pressure now. This evening, it hardly ever held over 5 psi, even when sitting still with the motor throttled up to a higher RPM. I just cannot figure out where the darn water is going.......

I've run out of ideas and time. I'm probably going to start pulling the Suzuki off the boat tomorrow evening and get my old motor re-mounted so I have time to deal with any potential issues it may have prior to leaving for my trip next week. If anyone has any good ideas left, I'm all ears (eyes). Otherwise, I'll probably just go through the thing carefully when I'm dis-assembling it for parts to see if perhaps I missed anything.

mphelle8vld, many thanks for your advice. It's great to have the help.

 

[mphelle8vld]

Re: 1987 Suzuki DT85 overheats at high RPM

Disassemble for parts? Say it ain't so. I'm sure you're pressed for time on the motor swap but did you ever figure a way to spin the driveshaft (drill) with the lower unit in a bucket? I'd sure want to see what the pump is putting out. Then I would use an old washer supply hose with the male end cut off, it fits over the end of the water tube on a DT65 anyway, to see where the water is going and what pressure you see.

 

[mkrussow]

Re: 1987 Suzuki DT85 overheats at high RPM

I appreciate the words of encouragement

I figured out a way to spin the main shaft (I think), but have not done it. The problem is most drills are only good to, at most, 1000 rpms. I wasn't confident that I'd find anything at that speed. You are right that it won't take much to do it and it may prove beneficial. I may just "buck up" this evening and rig something up as it won't cost me much time.

I'm now also struggling with a carbeurator issue (I think). The motor starts and idles fairly well when cold, but once it gets warm it won't idle at all. This problem has been getting worse the last few times I've had the boat out. There were some very choice words spoken last night as I was trying to get the boat on the trailer by myself.

I may not give up on the motor completely and come back to it later, but I've got to get a running motor on my boat for my trip. My family will have some choice words for me if I don't have the boat ready.