75 or 110 Motor?

[pvh762000]

Hi everyone, I just bought a motor and the previous owner told me that it's a 1975 9.8HP motor. On the motor cover there is a label with the number 75 and then on the crowl there is a 9.8hp label. After reading this forum I noticed that there is a 75 model which is a 7.5HP motor and a 110 model which is a 9.8HP. My question is the 75 label stand for the year or does it stand for the model? If it stand for the model then that mean my motor is really a 7.5HP. I would find it odd to have the year on the motor cover. Or maybe someone took a 75 motor cover and put it on my motor? <br /><br />Is there a way to tell for sure what motor I have?

 

[rickdb1boat]

Re: 75 or 110 Motor?

I don't see the 9.8 going back to 1975. Looks like it takes off in 1979. I do see the 75 (7.5) that goes back to 1969. If it has "75" on it, I would assume it is a 7.5 HP Motor, but I can't be 100% sure. Maybe others will know how to tell. Guess there is no title to the motor?? Look for serial numbers on the transom bracket(Tag)...

 

[pvh762000]

Re: 75 or 110 Motor?

I think the 9.8hp is the 110 model. The serial number is 4247526. I checked the serial # and it is within the range of the 75 and 110 models. So this doesn't help me identify which model it is. <br /><br />Can anyone help?

 

[rickdb1boat]

Re: 75 or 110 Motor?

110 (11,0) 4079000 - 4304784 1975 2 cyl<br /><br /><br />75 (7,5) 4085865 - 4314384 1975 2 cyl<br /><br />Yeah, either way it's a 75' model. Wait for others who know more on the Mercs...

 

[rickdb1boat]

Re: 75 or 110 Motor?

Here's a small difference that may or may not tell the difference:<br /><br />Coil #33(9)-5288T2 (7.5)<br /><br />Coil #33(6)-5288T2 (110)<br /><br />Might see if you can find the part # on the coils....

 

[pvh762000]

Re: 75 or 110 Motor?

Rick, where did you see the 33(6)-5288T2. I checked http://www.mercruiserparts.com and found 33(9)-5288T2 for both models.

 

[rickdb1boat]

Re: 75 or 110 Motor?

I found it at this site, but that may have been a goof-up on their part...<br /><br /> web page

 

[pvh762000]

Re: 75 or 110 Motor?

I'll wait for comments from other people. Thank you for your help.

 

[Chinewalker]

Re: 75 or 110 Motor?

The 7.5 and 9.8 share the block casting, and both are approximately 11-cubic inches in displacement. However, the 9.8hp is ported differently for better breathing and that's where it gains the extra 33% in power. <br /><br />The memory is a little fuzzy on this, but the easiest way to tell is to look at the block. I'm pretty sure all of the 11-cube blocks are embossed with the word "Lightning". One of the blocks has the word "Comet" on a sticker on the side of the block, and I'm fairly certain it was the smaller ported 7.5 version that had the sticker.. If I've got that backwards, I'm sure someone will rectify it for me....<br />- Scott

 

[pvh762000]

Re: 75 or 110 Motor?

I noticed the Lightning on the blocks. I also remembered seeing a sticker on the block as well. I will check on this when I get home. <br /><br />Any idea on the motor cover with the sticker 75 on it?

 

[joblo33]

Re: 75 or 110 Motor?

Yes, "comet" is on the 7.5hp. Both the 9.8hp and the 7.5 date back to the 60's. Sounds like either your Motor cover or cowling isn't original, probably the cowl as it's easier to swap.<br />Here's a 1975 Merc 9.8hp:<br />

<br />Eric

 

[pvh762000]

Re: 75 or 110 Motor?

My motor looks exactly like that. But with the 75 on the cover. It has the Lightning on the block.<br /><br />So do you think the motor cover could be swap?

 

[pvh762000]

Re: 75 or 110 Motor?

Another question, does the 7.5HP also have the Lightning on the block in addition to the Comet sticker or just the Comet sticker?<br /><br />I only see Lightning on my block and no sticker.<br /><br />I want to make sure that the previous owner didn't rip me off.

 

[Chinewalker]

Re: 75 or 110 Motor?

Yes, both blocks have the Lightning designation as that was actually cast into the block. The sticker was to note how it was machined after it was cast. The sticker means it has the small ports, no sticker means it has the larger ports (or someone removed the sticker).<br />- Scott

 

[pvh762000]

Re: 75 or 110 Motor?

Can you tell me where the sticker is located? I noticed a spot on the exhaust manifold cover where a sticker could have been removed.

 

[Chinewalker]

Re: 75 or 110 Motor?

Hi PVH,<br /> The sticker would be on the intake side of the block, right near the cast-in Lightning. The sticker on the exhaust cover was likely either the "OK" sticker with the test run date or the one that recommends Champion Perma Gap plugs.<br />- Scott

 

[pvh762000]

Re: 75 or 110 Motor?

Thank you everyone for your help. I would conclude that my motor is a 9.8hp since I did not see any sticker mark near the Lightning cast. I guess the previous owner swapped the cover with a 75 model cover.<br /><br />I have a couple more questions to ask. I just tried changing the impeller on the motor. When I took the water pump cover off the drive shaft I noticed a black rubber washer fell off. I didn't pay attention to where that washer came from. Can someone help me figure where this washer go to? My guess is the washer goes on top of the water pump cover but does it just sit on top of the cover with nothing holding it down, if so what is the purpose of this washer?<br /><br />Another question is where is the zinc anode plate for this motor? I can't seem to find it.

 

[joblo33]

Re: 75 or 110 Motor?

If it's a thick rubber washer it sits on top of the water pump, if it's a o-ring there's a groove near the top of the driveshaft on some models where that would go.<br />Eric

 

[pvh762000]

Re: 75 or 110 Motor?

Thank you Eric.<br /><br />Do you have an anode plate on your 9.8 hp motor? I can't seem to find where mine is.

 

[joblo33]

Re: 75 or 110 Motor?

I don't think the 9.8's and 7.5's have anodes, but one of my 7.5's has one bolted onto the anti-cavitation plate aftermarket.<br />Eric<br /><br />EDIT: This leg has an anode bolted on:<br />

<br />(notice the two bolts on the bottom of the anti-cav plate)